commit d8794ac20a299b647ba9958f6d657051fc51a540 upstream.
As Andrew pointed out, it will make sense that the PTP core
checked timespec64 struct's tv_sec and tv_nsec range before calling
ptp->info->settime64().
As the man manual of clock_settime() said, if tp.tv_sec is negative or
tp.tv_nsec is outside the range [0..999,999,999], it should return EINVAL,
which include dynamic clocks which handles PTP clock, and the condition is
consistent with timespec64_valid(). As Thomas suggested, timespec64_valid()
only check the timespec is valid, but not ensure that the time is
in a valid range, so check it ahead using timespec64_valid_strict()
in pc_clock_settime() and return -EINVAL if not valid.
There are some drivers that use tp->tv_sec and tp->tv_nsec directly to
write registers without validity checks and assume that the higher layer
has checked it, which is dangerous and will benefit from this, such as
hclge_ptp_settime(), igb_ptp_settime_i210(), _rcar_gen4_ptp_settime(),
and some drivers can remove the checks of itself.
Cc: stable@vger.kernel.org
Fixes: 0606f422b4 ("posix clocks: Introduce dynamic clocks")
Acked-by: Richard Cochran <richardcochran@gmail.com>
Suggested-by: Andrew Lunn <andrew@lunn.ch>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Link: https://patch.msgid.link/20241009072302.1754567-2-ruanjinjie@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 5a830bbce3af16833fe0092dec47b6dd30279825 ]
The hrtimer function callback must not be NULL. It has to be specified by
the call side but it is not validated by the hrtimer code. When a hrtimer
is queued without a function callback, the kernel crashes with a null
pointer dereference when trying to execute the callback in __run_hrtimer().
Introduce a validation before queuing the hrtimer in
hrtimer_start_range_ns().
[anna-maria: Rephrase commit message]
Signed-off-by: Phil Chang <phil.chang@mediatek.com>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit d0304569fb019d1bcfbbbce1ce6df6b96f04079b ]
Kernel timekeeping is designed to keep the change in cycles (since the last
timer interrupt) below max_cycles, which prevents multiplication overflow
when converting cycles to nanoseconds. However, if timer interrupts stop,
the clocksource_cyc2ns() calculation will eventually overflow.
Add protection against that. Simplify by folding together
clocksource_delta() and clocksource_cyc2ns() into cycles_to_nsec_safe().
Check against max_cycles, falling back to a slower higher precision
calculation.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240325064023.2997-20-adrian.hunter@intel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 3ce74f1a8566dbbc9774f85fb0ce781fe290fd32 ]
tick_nohz_idle_got_tick() is called by cpuidle_reflect() within the idle
loop with interrupts enabled. This function modifies the struct
tick_sched's bitfield "got_idle_tick". However this bitfield is stored
within the same mask as other bitfields that can be modified from
interrupts.
Fortunately so far it looks like the only race that can happen is while
writing ->got_idle_tick to 0, an interrupt fires and writes the
->idle_active field to 0. It's then possible that the interrupted write
to ->got_idle_tick writes back the old value of ->idle_active back to 1.
However if that happens, the worst possible outcome is that the time
spent between that interrupt and the upcoming call to
tick_nohz_idle_exit() is accounted as idle, which is negligible quantity.
Still all the bitfield writes within this struct tick_sched's shadow
mask should be IRQ-safe. Therefore move this bitfield out to its own
storage to avoid further suprises.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-12-frederic@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 56c2cb10120894be40c40a9bf0ce798da14c50f6 ]
During CPU-down hotplug, hrtimers may migrate to isolated CPUs,
compromising CPU isolation.
Address this issue by masking valid CPUs for hrtimers using
housekeeping_cpumask(HK_TYPE_TIMER).
Suggested-by: Waiman Long <longman@redhat.com>
Signed-off-by: Costa Shulyupin <costa.shul@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20240222200856.569036-1-costa.shul@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 5916be8a53de6401871bdd953f6c60237b47d6d3 upstream.
The addition of the bases argument to clock_was_set() fixed up all call
sites correctly except for do_adjtimex(). This uses CLOCK_REALTIME
instead of CLOCK_SET_WALL as argument. CLOCK_REALTIME is 0.
As a result the effect of that clock_was_set() notification is incomplete
and might result in timers expiring late because the hrtimer code does
not re-evaluate the affected clock bases.
Use CLOCK_SET_WALL instead of CLOCK_REALTIME to tell the hrtimers code
which clock bases need to be re-evaluated.
Fixes: 17a1b8826b ("hrtimer: Add bases argument to clock_was_set()")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/877ccx7igo.ffs@tglx
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 06c03c8edce333b9ad9c6b207d93d3a5ae7c10c0 upstream.
Using syzkaller with the recently reintroduced signed integer overflow
sanitizer produces this UBSAN report:
UBSAN: signed-integer-overflow in ../kernel/time/ntp.c:738:18
9223372036854775806 + 4 cannot be represented in type 'long'
Call Trace:
handle_overflow+0x171/0x1b0
__do_adjtimex+0x1236/0x1440
do_adjtimex+0x2be/0x740
The user supplied time_constant value is incremented by four and then
clamped to the operating range.
Before commit eea83d896e ("ntp: NTP4 user space bits update") the user
supplied value was sanity checked to be in the operating range. That change
removed the sanity check and relied on clamping after incrementing which
does not work correctly when the user supplied value is in the overflow
zone of the '+ 4' operation.
The operation requires CAP_SYS_TIME and the side effect of the overflow is
NTP getting out of sync.
Similar to the fixups for time_maxerror and time_esterror, clamp the user
space supplied value to the operating range.
[ tglx: Switch to clamping ]
Fixes: eea83d896e ("ntp: NTP4 user space bits update")
Signed-off-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Miroslav Lichvar <mlichvar@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20240517-b4-sio-ntp-c-v2-1-f3a80096f36f@google.com
Closes: https://github.com/KSPP/linux/issues/352
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit f2655ac2c06a15558e51ed6529de280e1553c86e ]
The current "nretries > 1 || nretries >= max_retries" check in
cs_watchdog_read() will always evaluate to true, and thus pr_warn(), if
nretries is greater than 1. The intent is instead to never warn on the
first try, but otherwise warn if the successful retry was the last retry.
Therefore, change that "||" to "&&".
Fixes: db3a34e174 ("clocksource: Retry clock read if long delays detected")
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20240802154618.4149953-2-paulmck@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 2ed08e4bc53298db3f87b528cd804cb0cce066a9 ]
On a 8-socket server the TSC is wrongly marked as 'unstable' and disabled
during boot time on about one out of 120 boot attempts:
clocksource: timekeeping watchdog on CPU227: wd-tsc-wd excessive read-back delay of 153560ns vs. limit of 125000ns,
wd-wd read-back delay only 11440ns, attempt 3, marking tsc unstable
tsc: Marking TSC unstable due to clocksource watchdog
TSC found unstable after boot, most likely due to broken BIOS. Use 'tsc=unstable'.
sched_clock: Marking unstable (119294969739, 159204297)<-(125446229205, -5992055152)
clocksource: Checking clocksource tsc synchronization from CPU 319 to CPUs 0,99,136,180,210,542,601,896.
clocksource: Switched to clocksource hpet
The reason is that for platform with a large number of CPUs, there are
sporadic big or huge read latencies while reading the watchog/clocksource
during boot or when system is under stress work load, and the frequency and
maximum value of the latency goes up with the number of online CPUs.
The cCurrent code already has logic to detect and filter such high latency
case by reading the watchdog twice and checking the two deltas. Due to the
randomness of the latency, there is a low probabilty that the first delta
(latency) is big, but the second delta is small and looks valid. The
watchdog code retries the readouts by default twice, which is not
necessarily sufficient for systems with a large number of CPUs.
There is a command line parameter 'max_cswd_read_retries' which allows to
increase the number of retries, but that's not user friendly as it needs to
be tweaked per system. As the number of required retries is proportional to
the number of online CPUs, this parameter can be calculated at runtime.
Scale and enlarge the number of retries according to the number of online
CPUs and remove the command line parameter completely.
[ tglx: Massaged change log and comments ]
Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jin Wang <jin1.wang@intel.com>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Waiman Long <longman@redhat.com>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20240221060859.1027450-1-feng.tang@intel.com
Stable-dep-of: f2655ac2c06a ("clocksource: Fix brown-bag boolean thinko in cs_watchdog_read()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 87d571d6fb77ec342a985afa8744bb9bb75b3622 ]
Using syzkaller alongside the newly reintroduced signed integer overflow
sanitizer spits out this report:
UBSAN: signed-integer-overflow in ../kernel/time/ntp.c:461:16
9223372036854775807 + 500 cannot be represented in type 'long'
Call Trace:
handle_overflow+0x171/0x1b0
second_overflow+0x2d6/0x500
accumulate_nsecs_to_secs+0x60/0x160
timekeeping_advance+0x1fe/0x890
update_wall_time+0x10/0x30
time_maxerror is unconditionally incremented and the result is checked
against NTP_PHASE_LIMIT, but the increment itself can overflow, resulting
in wrap-around to negative space.
Before commit eea83d896e ("ntp: NTP4 user space bits update") the user
supplied value was sanity checked to be in the operating range. That change
removed the sanity check and relied on clamping in handle_overflow() which
does not work correctly when the user supplied value is in the overflow
zone of the '+ 500' operation.
The operation requires CAP_SYS_TIME and the side effect of the overflow is
NTP getting out of sync.
Miroslav confirmed that the input value should be clamped to the operating
range and the same applies to time_esterror. The latter is not used by the
kernel, but the value still should be in the operating range as it was
before the sanity check got removed.
Clamp them to the operating range.
[ tglx: Changed it to clamping and included time_esterror ]
Fixes: eea83d896e ("ntp: NTP4 user space bits update")
Signed-off-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Miroslav Lichvar <mlichvar@redhat.com>
Link: https://lore.kernel.org/all/20240517-b4-sio-ntp-usec-v2-1-d539180f2b79@google.com
Closes: https://github.com/KSPP/linux/issues/354
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 6881e75237a84093d0986f56223db3724619f26e upstream.
The recent fix for making the take over of the broadcast timer more
reliable retrieves a per CPU pointer in preemptible context.
This went unnoticed as compilers hoist the access into the non-preemptible
region where the pointer is actually used. But of course it's valid that
the compiler keeps it at the place where the code puts it which rightfully
triggers:
BUG: using smp_processor_id() in preemptible [00000000] code:
caller is hotplug_cpu__broadcast_tick_pull+0x1c/0xc0
Move it to the actual usage site which is in a non-preemptible region.
Fixes: f7d43dd206e7 ("tick/broadcast: Make takeover of broadcast hrtimer reliable")
Reported-by: David Wang <00107082@163.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Yu Liao <liaoyu15@huawei.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/87ttg56ers.ffs@tglx
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit f7d43dd206e7e18c182f200e67a8db8c209907fa upstream.
Running the LTP hotplug stress test on a aarch64 machine results in
rcu_sched stall warnings when the broadcast hrtimer was owned by the
un-plugged CPU. The issue is the following:
CPU1 (owns the broadcast hrtimer) CPU2
tick_broadcast_enter()
// shutdown local timer device
broadcast_shutdown_local()
...
tick_broadcast_exit()
clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT)
// timer device is not programmed
cpumask_set_cpu(cpu, tick_broadcast_force_mask)
initiates offlining of CPU1
take_cpu_down()
/*
* CPU1 shuts down and does not
* send broadcast IPI anymore
*/
takedown_cpu()
hotplug_cpu__broadcast_tick_pull()
// move broadcast hrtimer to this CPU
clockevents_program_event()
bc_set_next()
hrtimer_start()
/*
* timer device is not programmed
* because only the first expiring
* timer will trigger clockevent
* device reprogramming
*/
What happens is that CPU2 exits broadcast mode with force bit set, then the
local timer device is not reprogrammed and CPU2 expects to receive the
expired event by the broadcast IPI. But this does not happen because CPU1
is offlined by CPU2. CPU switches the clockevent device to ONESHOT state,
but does not reprogram the device.
The subsequent reprogramming of the hrtimer broadcast device does not
program the clockevent device of CPU2 either because the pending expiry
time is already in the past and the CPU expects the event to be delivered.
As a consequence all CPUs which wait for a broadcast event to be delivered
are stuck forever.
Fix this issue by reprogramming the local timer device if the broadcast
force bit of the CPU is set so that the broadcast hrtimer is delivered.
[ tglx: Massage comment and change log. Add Fixes tag ]
Fixes: 989dcb645c ("tick: Handle broadcast wakeup of multiple cpus")
Signed-off-by: Yu Liao <liaoyu15@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240711124843.64167-1-liaoyu15@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 07c54cc5988f19c9642fd463c2dbdac7fc52f777 upstream.
After the recent commit 5097cbcb38e6 ("sched/isolation: Prevent boot crash
when the boot CPU is nohz_full") the kernel no longer crashes, but there is
another problem.
In this case tick_setup_device() calls tick_take_do_timer_from_boot() to
update tick_do_timer_cpu and this triggers the WARN_ON_ONCE(irqs_disabled)
in smp_call_function_single().
Kill tick_take_do_timer_from_boot() and just use WRITE_ONCE(), the new
comment explains why this is safe (thanks Thomas!).
Fixes: 08ae95f4fd ("nohz_full: Allow the boot CPU to be nohz_full")
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240528122019.GA28794@redhat.com
Link: https://lore.kernel.org/all/20240522151742.GA10400@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 14274d0bd31b4debf28284604589f596ad2e99f2 ]
So far, get_device_system_crosststamp() unconditionally passes
system_counterval.cycles to timekeeping_cycles_to_ns(). But when
interpolating system time (do_interp == true), system_counterval.cycles is
before tkr_mono.cycle_last, contrary to the timekeeping_cycles_to_ns()
expectations.
On x86, CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE will mitigate on
interpolating, setting delta to 0. With delta == 0, xtstamp->sys_monoraw
and xtstamp->sys_realtime are then set to the last update time, as
implicitly expected by adjust_historical_crosststamp(). On other
architectures, the resulting nonsense xtstamp->sys_monoraw and
xtstamp->sys_realtime corrupt the xtstamp (ts) adjustment in
adjust_historical_crosststamp().
Fix this by deriving xtstamp->sys_monoraw and xtstamp->sys_realtime from
the last update time when interpolating, by using the local variable
"cycles". The local variable already has the right value when
interpolating, unlike system_counterval.cycles.
Fixes: 2c756feb18 ("time: Add history to cross timestamp interface supporting slower devices")
Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/r/20231218073849.35294-4-peter.hilber@opensynergy.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 87a41130881995f82f7adbafbfeddaebfb35f0ef ]
The cycle_between() helper checks if parameter test is in the open interval
(before, after). Colloquially speaking, this also applies to the counter
wrap-around special case before > after. get_device_system_crosststamp()
currently uses cycle_between() at the first call site to decide whether to
interpolate for older counter readings.
get_device_system_crosststamp() has the following problem with
cycle_between() testing against an open interval: Assume that, by chance,
cycles == tk->tkr_mono.cycle_last (in the following, "cycle_last" for
brevity). Then, cycle_between() at the first call site, with effective
argument values cycle_between(cycle_last, cycles, now), returns false,
enabling interpolation. During interpolation,
get_device_system_crosststamp() will then call cycle_between() at the
second call site (if a history_begin was supplied). The effective argument
values are cycle_between(history_begin->cycles, cycles, cycles), since
system_counterval.cycles == interval_start == cycles, per the assumption.
Due to the test against the open interval, cycle_between() returns false
again. This causes get_device_system_crosststamp() to return -EINVAL.
This failure should be avoided, since get_device_system_crosststamp() works
both when cycles follows cycle_last (no interpolation), and when cycles
precedes cycle_last (interpolation). For the case cycles == cycle_last,
interpolation is actually unneeded.
Fix this by changing cycle_between() into timestamp_in_interval(), which
now checks against the closed interval, rather than the open interval.
This changes the get_device_system_crosststamp() behavior for three corner
cases:
1. Bypass interpolation in the case cycles == tk->tkr_mono.cycle_last,
fixing the problem described above.
2. At the first timestamp_in_interval() call site, cycles == now no longer
causes failure.
3. At the second timestamp_in_interval() call site, history_begin->cycles
== system_counterval.cycles no longer causes failure.
adjust_historical_crosststamp() also works for this corner case,
where partial_history_cycles == total_history_cycles.
These behavioral changes should not cause any problems.
Fixes: 2c756feb18 ("time: Add history to cross timestamp interface supporting slower devices")
Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20231218073849.35294-3-peter.hilber@opensynergy.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 84dccadd3e2a3f1a373826ad71e5ced5e76b0c00 ]
cycle_between() decides whether get_device_system_crosststamp() will
interpolate for older counter readings.
cycle_between() yields wrong results for a counter wrap-around where after
< before < test, and for the case after < test < before.
Fix the comparison logic.
Fixes: 2c756feb18 ("time: Add history to cross timestamp interface supporting slower devices")
Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/r/20231218073849.35294-2-peter.hilber@opensynergy.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 133e267ef4a26d19c93996a874714e9f3f8c70aa ]
'days' is a s64 (from div_s64), and so should use a %lld specifier.
This was found by extending KUnit's assertion macros to use gcc's
__printf attribute.
Fixes: 2760105516 ("time: Improve performance of time64_to_tm()")
Signed-off-by: David Gow <davidgow@google.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit dad6a09f3148257ac1773cd90934d721d68ab595 upstream.
The hrtimers migration on CPU-down hotplug process has been moved
earlier, before the CPU actually goes to die. This leaves a small window
of opportunity to queue an hrtimer in a blind spot, leaving it ignored.
For example a practical case has been reported with RCU waking up a
SCHED_FIFO task right before the CPUHP_AP_IDLE_DEAD stage, queuing that
way a sched/rt timer to the local offline CPU.
Make sure such situations never go unnoticed and warn when that happens.
Fixes: 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier")
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240129235646.3171983-4-boqun.feng@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 9a574ea9069be30b835a3da772c039993c43369b upstream.
Commit 71fee48f ("tick-sched: Fix idle and iowait sleeptime accounting vs
CPU hotplug") preserved total idle sleep time and iowait sleeptime across
CPU hotplug events.
Similar reasoning applies to the number of idle calls and idle sleeps to
get the proper average of sleep time per idle invocation.
Preserve those fields too.
Fixes: 71fee48f ("tick-sched: Fix idle and iowait sleeptime accounting vs CPU hotplug")
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240122233534.3094238-1-tim.c.chen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 644649553508b9bacf0fc7a5bdc4f9e0165576a5 upstream.
There have been reports of the watchdog marking clocksources unstable on
machines with 8 NUMA nodes:
clocksource: timekeeping watchdog on CPU373:
Marking clocksource 'tsc' as unstable because the skew is too large:
clocksource: 'hpet' wd_nsec: 14523447520
clocksource: 'tsc' cs_nsec: 14524115132
The measured clocksource skew - the absolute difference between cs_nsec
and wd_nsec - was 668 microseconds:
cs_nsec - wd_nsec = 14524115132 - 14523447520 = 667612
The kernel used 200 microseconds for the uncertainty_margin of both the
clocksource and watchdog, resulting in a threshold of 400 microseconds (the
md variable). Both the cs_nsec and the wd_nsec value indicate that the
readout interval was circa 14.5 seconds. The observed behaviour is that
watchdog checks failed for large readout intervals on 8 NUMA node
machines. This indicates that the size of the skew was directly proportinal
to the length of the readout interval on those machines. The measured
clocksource skew, 668 microseconds, was evaluated against a threshold (the
md variable) that is suited for readout intervals of roughly
WATCHDOG_INTERVAL, i.e. HZ >> 1, which is 0.5 second.
The intention of 2e27e793e2 ("clocksource: Reduce clocksource-skew
threshold") was to tighten the threshold for evaluating skew and set the
lower bound for the uncertainty_margin of clocksources to twice
WATCHDOG_MAX_SKEW. Later in c37e85c135 ("clocksource: Loosen clocksource
watchdog constraints"), the WATCHDOG_MAX_SKEW constant was increased to
125 microseconds to fit the limit of NTP, which is able to use a
clocksource that suffers from up to 500 microseconds of skew per second.
Both the TSC and the HPET use default uncertainty_margin. When the
readout interval gets stretched the default uncertainty_margin is no
longer a suitable lower bound for evaluating skew - it imposes a limit
that is far stricter than the skew with which NTP can deal.
The root causes of the skew being directly proportinal to the length of
the readout interval are:
* the inaccuracy of the shift/mult pairs of clocksources and the watchdog
* the conversion to nanoseconds is imprecise for large readout intervals
Prevent this by skipping the current watchdog check if the readout
interval exceeds 2 * WATCHDOG_INTERVAL. Considering the maximum readout
interval of 2 * WATCHDOG_INTERVAL, the current default uncertainty margin
(of the TSC and HPET) corresponds to a limit on clocksource skew of 250
ppm (microseconds of skew per second). To keep the limit imposed by NTP
(500 microseconds of skew per second) for all possible readout intervals,
the margins would have to be scaled so that the threshold value is
proportional to the length of the actual readout interval.
As for why the readout interval may get stretched: Since the watchdog is
executed in softirq context the expiration of the watchdog timer can get
severely delayed on account of a ksoftirqd thread not getting to run in a
timely manner. Surely, a system with such belated softirq execution is not
working well and the scheduling issue should be looked into but the
clocksource watchdog should be able to deal with it accordingly.
Fixes: 2e27e793e2 ("clocksource: Reduce clocksource-skew threshold")
Suggested-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Jiri Wiesner <jwiesner@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Feng Tang <feng.tang@intel.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240122172350.GA740@incl
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 71fee48fb772ac4f6cfa63dbebc5629de8b4cc09 upstream.
When offlining and onlining CPUs the overall reported idle and iowait
times as reported by /proc/stat jump backward and forward:
cpu 132 0 176 225249 47 6 6 21 0 0
cpu0 80 0 115 112575 33 3 4 18 0 0
cpu1 52 0 60 112673 13 3 1 2 0 0
cpu 133 0 177 226681 47 6 6 21 0 0
cpu0 80 0 116 113387 33 3 4 18 0 0
cpu 133 0 178 114431 33 6 6 21 0 0 <---- jump backward
cpu0 80 0 116 114247 33 3 4 18 0 0
cpu1 52 0 61 183 0 3 1 2 0 0 <---- idle + iowait start with 0
cpu 133 0 178 228956 47 6 6 21 0 0 <---- jump forward
cpu0 81 0 117 114929 33 3 4 18 0 0
Reason for this is that get_idle_time() in fs/proc/stat.c has different
sources for both values depending on if a CPU is online or offline:
- if a CPU is online the values may be taken from its per cpu
tick_cpu_sched structure
- if a CPU is offline the values are taken from its per cpu cpustat
structure
The problem is that the per cpu tick_cpu_sched structure is set to zero on
CPU offline. See tick_cancel_sched_timer() in kernel/time/tick-sched.c.
Therefore when a CPU is brought offline and online afterwards both its idle
and iowait sleeptime will be zero, causing a jump backward in total system
idle and iowait sleeptime. In a similar way if a CPU is then brought
offline again the total idle and iowait sleeptimes will jump forward.
It looks like this behavior was introduced with commit 4b0c0f294f
("tick: Cleanup NOHZ per cpu data on cpu down").
This was only noticed now on s390, since we switched to generic idle time
reporting with commit be76ea6144 ("s390/idle: remove arch_cpu_idle_time()
and corresponding code").
Fix this by preserving the values of idle_sleeptime and iowait_sleeptime
members of the per-cpu tick_sched structure on CPU hotplug.
Fixes: 4b0c0f294f ("tick: Cleanup NOHZ per cpu data on cpu down")
Reported-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20240115163555.1004144-1-hca@linux.ibm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit a4aebe936554dac6a91e5d091179c934f8325708 ]
Only the posix timer system calls use this (when the posix timer support
is disabled, which does not actually happen in any normal case), because
they had debug code to print out a warning about missing system calls.
Get rid of that special case, and just use the standard COND_SYSCALL
interface that creates weak system call stubs that return -ENOSYS for
when the system call does not exist.
This fixes a kCFI issue with the SYS_NI() hackery:
CFI failure at int80_emulation+0x67/0xb0 (target: sys_ni_posix_timers+0x0/0x70; expected type: 0xb02b34d9)
WARNING: CPU: 0 PID: 48 at int80_emulation+0x67/0xb0
Reported-by: kernel test robot <oliver.sang@intel.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sami Tolvanen <samitolvanen@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 5c0930ccaad5a74d74e8b18b648c5eb21ed2fe94 ]
2b8272ff4a ("cpu/hotplug: Prevent self deadlock on CPU hot-unplug")
solved the straight forward CPU hotplug deadlock vs. the scheduler
bandwidth timer. Yu discovered a more involved variant where a task which
has a bandwidth timer started on the outgoing CPU holds a lock and then
gets throttled. If the lock required by one of the CPU hotplug callbacks
the hotplug operation deadlocks because the unthrottling timer event is not
handled on the dying CPU and can only be recovered once the control CPU
reaches the hotplug state which pulls the pending hrtimers from the dead
CPU.
Solve this by pushing the hrtimers away from the dying CPU in the dying
callbacks. Nothing can queue a hrtimer on the dying CPU at that point because
all other CPUs spin in stop_machine() with interrupts disabled and once the
operation is finished the CPU is marked offline.
Reported-by: Yu Liao <liaoyu15@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Liu Tie <liutie4@huawei.com>
Link: https://lore.kernel.org/r/87a5rphara.ffs@tglx
Signed-off-by: Sasha Levin <sashal@kernel.org>
kernels, caused by a buggy factoring-out of existing code.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'timers-urgent-2023-09-02' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fix from Ingo Molnar:
"Fix false positive 'softirq work is pending' messages on -rt kernels,
caused by a buggy factoring-out of existing code"
* tag 'timers-urgent-2023-09-02' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
tick/rcu: Fix false positive "softirq work is pending" messages
- Work from Carlos Bilbao to integrate rustdoc output into the generated
HTML documentation. This took some work to figure out how to do it
without slowing the docs build and without creating people who don't have
Rust installed, but Carlos got there.
- Move the loongarch and mips architecture documentation under
Documentation/arch/.
- Some more maintainer documentation from Jakub
...plus the usual assortment of updates, translations, and fixes.
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Merge tag 'docs-6.6' of git://git.lwn.net/linux
Pull documentation updates from Jonathan Corbet:
"Documentation work keeps chugging along; this includes:
- Work from Carlos Bilbao to integrate rustdoc output into the
generated HTML documentation. This took some work to figure out how
to do it without slowing the docs build and without creating people
who don't have Rust installed, but Carlos got there
- Move the loongarch and mips architecture documentation under
Documentation/arch/
- Some more maintainer documentation from Jakub
... plus the usual assortment of updates, translations, and fixes"
* tag 'docs-6.6' of git://git.lwn.net/linux: (56 commits)
Docu: genericirq.rst: fix irq-example
input: docs: pxrc: remove reference to phoenix-sim
Documentation: serial-console: Fix literal block marker
docs/mm: remove references to hmm_mirror ops and clean typos
docs/zh_CN: correct regi_chg(),regi_add() to region_chg(),region_add()
Documentation: Fix typos
Documentation/ABI: Fix typos
scripts: kernel-doc: fix macro handling in enums
scripts: kernel-doc: parse DEFINE_DMA_UNMAP_[ADDR|LEN]
Documentation: riscv: Update boot image header since EFI stub is supported
Documentation: riscv: Add early boot document
Documentation: arm: Add bootargs to the table of added DT parameters
docs: kernel-parameters: Refer to the correct bitmap function
doc: update params of memhp_default_state=
docs: Add book to process/kernel-docs.rst
docs: sparse: fix invalid link addresses
docs: vfs: clean up after the iterate() removal
docs: Add a section on surveys to the researcher guidelines
docs: move mips under arch
docs: move loongarch under arch
...
In commit 0345691b24 ("tick/rcu: Stop allowing RCU_SOFTIRQ in idle") the
new function report_idle_softirq() was created by breaking code out of the
existing can_stop_idle_tick() for kernels v5.18 and newer.
In doing so, the code essentially went from a one conditional:
if (a && b && c)
warn();
to a three conditional:
if (!a)
return;
if (!b)
return;
if (!c)
return;
warn();
But that conversion got the condition for the RT specific
local_bh_blocked() wrong. The original condition was:
!local_bh_blocked()
but the conversion failed to negate it so it ended up as:
if (!local_bh_blocked())
return false;
This issue lay dormant until another fixup for the same commit was added
in commit a7e282c777 ("tick/rcu: Fix bogus ratelimit condition").
This commit realized the ratelimit was essentially set to zero instead
of ten, and hence *no* softirq pending messages would ever be issued.
Once this commit was backported via linux-stable, both the v6.1 and v6.4
preempt-rt kernels started printing out 10 instances of this at boot:
NOHZ tick-stop error: local softirq work is pending, handler #80!!!
Remove the negation and return when local_bh_blocked() evaluates to true to
bring the correct behaviour back.
Fixes: 0345691b24 ("tick/rcu: Stop allowing RCU_SOFTIRQ in idle")
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Reviewed-by: Wen Yang <wenyang.linux@foxmail.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230818200757.1808398-1-paul.gortmaker@windriver.com
This kunit update for Linux 6.6.rc1 consists of:
-- Adds support for running Rust documentation tests as KUnit tests
-- Makes init, str, sync, types doctests compilable/testable
-- Adds support for attributes API which include speed, modules
attributes, ability to filter and report attributes.
-- Adds support for marking tests slow using attributes API.
-- Adds attributes API documentation
-- Fixes to wild-memory-access bug in kunit_filter_suites() and
a possible memory leak in kunit_filter_suites()
-- Adds support for counting number of test suites in a module, list
action to kunit test modules, and test filtering on module tests.
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Merge tag 'linux-kselftest-kunit-6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest
Pull kunit updates from Shuah Khan:
- add support for running Rust documentation tests as KUnit tests
- make init, str, sync, types doctests compilable/testable
- add support for attributes API which include speed, modules
attributes, ability to filter and report attributes
- add support for marking tests slow using attributes API
- add attributes API documentation
- fix a wild-memory-access bug in kunit_filter_suites() and a possible
memory leak in kunit_filter_suites()
- add support for counting number of test suites in a module, list
action to kunit test modules, and test filtering on module tests
* tag 'linux-kselftest-kunit-6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest: (25 commits)
kunit: fix struct kunit_attr header
kunit: replace KUNIT_TRIGGER_STATIC_STUB maro with KUNIT_STATIC_STUB_REDIRECT
kunit: Allow kunit test modules to use test filtering
kunit: Make 'list' action available to kunit test modules
kunit: Report the count of test suites in a module
kunit: fix uninitialized variables bug in attributes filtering
kunit: fix possible memory leak in kunit_filter_suites()
kunit: fix wild-memory-access bug in kunit_filter_suites()
kunit: Add documentation of KUnit test attributes
kunit: add tests for filtering attributes
kunit: time: Mark test as slow using test attributes
kunit: memcpy: Mark tests as slow using test attributes
kunit: tool: Add command line interface to filter and report attributes
kunit: Add ability to filter attributes
kunit: Add module attribute
kunit: Add speed attribute
kunit: Add test attributes API structure
MAINTAINERS: add Rust KUnit files to the KUnit entry
rust: support running Rust documentation tests as KUnit ones
rust: types: make doctests compilable/testable
...
Mark the time KUnit test, time64_to_tm_test_date_range, as slow using test
attributes.
This test ran relatively much slower than most other KUnit tests.
By marking this test as slow, the test can now be filtered using the KUnit
test attribute filtering feature. Example: --filter "speed>slow". This will
run only the tests that have speeds faster than slow. The slow attribute
will also be outputted in KTAP.
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Rae Moar <rmoar@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
The nanosecond-to-millisecond skew computation uses unsigned arithmetic,
which produces user-unfriendly large positive numbers for negative skews.
Therefore, use signed arithmetic for this computation in order to preserve
the negativity.
Reported-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Reported-by: Feng Tang <feng.tang@intel.com>
Fixes: dd02926994 ("clocksource: Improve "skew is too large" messages")
Reviewed-by: Feng Tang <feng.tang@intel.com>
Tested-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Add kernel-doc for all APIs that do not already have it.
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: John Stultz <jstultz@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Acked-by: John Stultz <jstultz@google.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20230704052405.5089-3-rdunlap@infradead.org
- Fix KMSAN vs FORTIFY in strlcpy/strlcat (Alexander Potapenko)
- Convert strreplace() to return string start (Andy Shevchenko)
- Flexible array conversions (Arnd Bergmann, Wyes Karny, Kees Cook)
- Add missing function prototypes seen with W=1 (Arnd Bergmann)
- Fix strscpy() kerndoc typo (Arne Welzel)
- Replace strlcpy() with strscpy() across many subsystems which were
either Acked by respective maintainers or were trivial changes that
went ignored for multiple weeks (Azeem Shaikh)
- Remove unneeded cc-option test for UBSAN_TRAP (Nick Desaulniers)
- Add KUnit tests for strcat()-family
- Enable KUnit tests of FORTIFY wrappers under UML
- Add more complete FORTIFY protections for strlcat()
- Add missed disabling of FORTIFY for all arch purgatories.
- Enable -fstrict-flex-arrays=3 globally
- Tightening UBSAN_BOUNDS when using GCC
- Improve checkpatch to check for strcpy, strncpy, and fake flex arrays
- Improve use of const variables in FORTIFY
- Add requested struct_size_t() helper for types not pointers
- Add __counted_by macro for annotating flexible array size members
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Merge tag 'hardening-v6.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull hardening updates from Kees Cook:
"There are three areas of note:
A bunch of strlcpy()->strscpy() conversions ended up living in my tree
since they were either Acked by maintainers for me to carry, or got
ignored for multiple weeks (and were trivial changes).
The compiler option '-fstrict-flex-arrays=3' has been enabled
globally, and has been in -next for the entire devel cycle. This
changes compiler diagnostics (though mainly just -Warray-bounds which
is disabled) and potential UBSAN_BOUNDS and FORTIFY _warning_
coverage. In other words, there are no new restrictions, just
potentially new warnings. Any new FORTIFY warnings we've seen have
been fixed (usually in their respective subsystem trees). For more
details, see commit df8fc4e934.
The under-development compiler attribute __counted_by has been added
so that we can start annotating flexible array members with their
associated structure member that tracks the count of flexible array
elements at run-time. It is possible (likely?) that the exact syntax
of the attribute will change before it is finalized, but GCC and Clang
are working together to sort it out. Any changes can be made to the
macro while we continue to add annotations.
As an example of that last case, I have a treewide commit waiting with
such annotations found via Coccinelle:
https://git.kernel.org/linus/adc5b3cb48a049563dc673f348eab7b6beba8a9b
Also see commit dd06e72e68 for more details.
Summary:
- Fix KMSAN vs FORTIFY in strlcpy/strlcat (Alexander Potapenko)
- Convert strreplace() to return string start (Andy Shevchenko)
- Flexible array conversions (Arnd Bergmann, Wyes Karny, Kees Cook)
- Add missing function prototypes seen with W=1 (Arnd Bergmann)
- Fix strscpy() kerndoc typo (Arne Welzel)
- Replace strlcpy() with strscpy() across many subsystems which were
either Acked by respective maintainers or were trivial changes that
went ignored for multiple weeks (Azeem Shaikh)
- Remove unneeded cc-option test for UBSAN_TRAP (Nick Desaulniers)
- Add KUnit tests for strcat()-family
- Enable KUnit tests of FORTIFY wrappers under UML
- Add more complete FORTIFY protections for strlcat()
- Add missed disabling of FORTIFY for all arch purgatories.
- Enable -fstrict-flex-arrays=3 globally
- Tightening UBSAN_BOUNDS when using GCC
- Improve checkpatch to check for strcpy, strncpy, and fake flex
arrays
- Improve use of const variables in FORTIFY
- Add requested struct_size_t() helper for types not pointers
- Add __counted_by macro for annotating flexible array size members"
* tag 'hardening-v6.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (54 commits)
netfilter: ipset: Replace strlcpy with strscpy
uml: Replace strlcpy with strscpy
um: Use HOST_DIR for mrproper
kallsyms: Replace all non-returning strlcpy with strscpy
sh: Replace all non-returning strlcpy with strscpy
of/flattree: Replace all non-returning strlcpy with strscpy
sparc64: Replace all non-returning strlcpy with strscpy
Hexagon: Replace all non-returning strlcpy with strscpy
kobject: Use return value of strreplace()
lib/string_helpers: Change returned value of the strreplace()
jbd2: Avoid printing outside the boundary of the buffer
checkpatch: Check for 0-length and 1-element arrays
riscv/purgatory: Do not use fortified string functions
s390/purgatory: Do not use fortified string functions
x86/purgatory: Do not use fortified string functions
acpi: Replace struct acpi_table_slit 1-element array with flex-array
clocksource: Replace all non-returning strlcpy with strscpy
string: use __builtin_memcpy() in strlcpy/strlcat
staging: most: Replace all non-returning strlcpy with strscpy
drm/i2c: tda998x: Replace all non-returning strlcpy with strscpy
...
- Scheduler SMP load-balancer improvements:
- Avoid unnecessary migrations within SMT domains on hybrid systems.
Problem:
On hybrid CPU systems, (processors with a mixture of higher-frequency
SMT cores and lower-frequency non-SMT cores), under the old code
lower-priority CPUs pulled tasks from the higher-priority cores if
more than one SMT sibling was busy - resulting in many unnecessary
task migrations.
Solution:
The new code improves the load balancer to recognize SMT cores with more
than one busy sibling and allows lower-priority CPUs to pull tasks, which
avoids superfluous migrations and lets lower-priority cores inspect all SMT
siblings for the busiest queue.
- Implement the 'runnable boosting' feature in the EAS balancer: consider CPU
contention in frequency, EAS max util & load-balance busiest CPU selection.
This improves CPU utilization for certain workloads, while leaves other key
workloads unchanged.
- Scheduler infrastructure improvements:
- Rewrite the scheduler topology setup code by consolidating it
into the build_sched_topology() helper function and building
it dynamically on the fly.
- Resolve the local_clock() vs. noinstr complications by rewriting
the code: provide separate sched_clock_noinstr() and
local_clock_noinstr() functions to be used in instrumentation code,
and make sure it is all instrumentation-safe.
- Fixes:
- Fix a kthread_park() race with wait_woken()
- Fix misc wait_task_inactive() bugs unearthed by the -rt merge:
- Fix UP PREEMPT bug by unifying the SMP and UP implementations.
- Fix task_struct::saved_state handling.
- Fix various rq clock update bugs, unearthed by turning on the rq clock
debugging code.
- Fix the PSI WINDOW_MIN_US trigger limit, which was easy to trigger by
creating enough cgroups, by removing the warnign and restricting
window size triggers to PSI file write-permission or CAP_SYS_RESOURCE.
- Propagate SMT flags in the topology when removing degenerate domain
- Fix grub_reclaim() calculation bug in the deadline scheduler code
- Avoid resetting the min update period when it is unnecessary, in
psi_trigger_destroy().
- Don't balance a task to its current running CPU in load_balance(),
which was possible on certain NUMA topologies with overlapping
groups.
- Fix the sched-debug printing of rq->nr_uninterruptible
- Cleanups:
- Address various -Wmissing-prototype warnings, as a preparation
to (maybe) enable this warning in the future.
- Remove unused code
- Mark more functions __init
- Fix shadow-variable warnings
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2023-06-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
"Scheduler SMP load-balancer improvements:
- Avoid unnecessary migrations within SMT domains on hybrid systems.
Problem:
On hybrid CPU systems, (processors with a mixture of
higher-frequency SMT cores and lower-frequency non-SMT cores),
under the old code lower-priority CPUs pulled tasks from the
higher-priority cores if more than one SMT sibling was busy -
resulting in many unnecessary task migrations.
Solution:
The new code improves the load balancer to recognize SMT cores
with more than one busy sibling and allows lower-priority CPUs
to pull tasks, which avoids superfluous migrations and lets
lower-priority cores inspect all SMT siblings for the busiest
queue.
- Implement the 'runnable boosting' feature in the EAS balancer:
consider CPU contention in frequency, EAS max util & load-balance
busiest CPU selection.
This improves CPU utilization for certain workloads, while leaves
other key workloads unchanged.
Scheduler infrastructure improvements:
- Rewrite the scheduler topology setup code by consolidating it into
the build_sched_topology() helper function and building it
dynamically on the fly.
- Resolve the local_clock() vs. noinstr complications by rewriting
the code: provide separate sched_clock_noinstr() and
local_clock_noinstr() functions to be used in instrumentation code,
and make sure it is all instrumentation-safe.
Fixes:
- Fix a kthread_park() race with wait_woken()
- Fix misc wait_task_inactive() bugs unearthed by the -rt merge:
- Fix UP PREEMPT bug by unifying the SMP and UP implementations
- Fix task_struct::saved_state handling
- Fix various rq clock update bugs, unearthed by turning on the rq
clock debugging code.
- Fix the PSI WINDOW_MIN_US trigger limit, which was easy to trigger
by creating enough cgroups, by removing the warnign and restricting
window size triggers to PSI file write-permission or
CAP_SYS_RESOURCE.
- Propagate SMT flags in the topology when removing degenerate domain
- Fix grub_reclaim() calculation bug in the deadline scheduler code
- Avoid resetting the min update period when it is unnecessary, in
psi_trigger_destroy().
- Don't balance a task to its current running CPU in load_balance(),
which was possible on certain NUMA topologies with overlapping
groups.
- Fix the sched-debug printing of rq->nr_uninterruptible
Cleanups:
- Address various -Wmissing-prototype warnings, as a preparation to
(maybe) enable this warning in the future.
- Remove unused code
- Mark more functions __init
- Fix shadow-variable warnings"
* tag 'sched-core-2023-06-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (50 commits)
sched/core: Avoid multiple calling update_rq_clock() in __cfsb_csd_unthrottle()
sched/core: Avoid double calling update_rq_clock() in __balance_push_cpu_stop()
sched/core: Fixed missing rq clock update before calling set_rq_offline()
sched/deadline: Update GRUB description in the documentation
sched/deadline: Fix bandwidth reclaim equation in GRUB
sched/wait: Fix a kthread_park race with wait_woken()
sched/topology: Mark set_sched_topology() __init
sched/fair: Rename variable cpu_util eff_util
arm64/arch_timer: Fix MMIO byteswap
sched/fair, cpufreq: Introduce 'runnable boosting'
sched/fair: Refactor CPU utilization functions
cpuidle: Use local_clock_noinstr()
sched/clock: Provide local_clock_noinstr()
x86/tsc: Provide sched_clock_noinstr()
clocksource: hyper-v: Provide noinstr sched_clock()
clocksource: hyper-v: Adjust hv_read_tsc_page_tsc() to avoid special casing U64_MAX
x86/vdso: Fix gettimeofday masking
math64: Always inline u128 version of mul_u64_u64_shr()
s390/time: Provide sched_clock_noinstr()
loongarch: Provide noinstr sched_clock_read()
...
- Core:
- A set of fixes, cleanups and enhancements to the posix timer code:
- Prevent another possible live lock scenario in the exit() path,
which affects POSIX_CPU_TIMERS_TASK_WORK enabled architectures.
- Fix a loop termination issue which was reported syzcaller/KSAN in
the posix timer ID allocation code.
That triggered a deeper look into the posix-timer code which
unearthed more small issues.
- Add missing READ/WRITE_ONCE() annotations
- Fix or remove completely outdated comments
- Document places which are subtle and completely undocumented.
- Add missing hrtimer modes to the trace event decoder
- Small cleanups and enhancements all over the place
- Drivers:
- Rework the Hyper-V clocksource and sched clock setup code
- Remove a deprecated clocksource driver
- Small fixes and enhancements all over the place
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Merge tag 'timers-core-2023-06-26' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"Time, timekeeping and related device driver updates:
Core:
- A set of fixes, cleanups and enhancements to the posix timer code:
- Prevent another possible live lock scenario in the exit() path,
which affects POSIX_CPU_TIMERS_TASK_WORK enabled architectures.
- Fix a loop termination issue which was reported syzcaller/KSAN
in the posix timer ID allocation code.
That triggered a deeper look into the posix-timer code which
unearthed more small issues.
- Add missing READ/WRITE_ONCE() annotations
- Fix or remove completely outdated comments
- Document places which are subtle and completely undocumented.
- Add missing hrtimer modes to the trace event decoder
- Small cleanups and enhancements all over the place
Drivers:
- Rework the Hyper-V clocksource and sched clock setup code
- Remove a deprecated clocksource driver
- Small fixes and enhancements all over the place"
* tag 'timers-core-2023-06-26' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/tip/tip: (39 commits)
clocksource/drivers/cadence-ttc: Fix memory leak in ttc_timer_probe
dt-bindings: timers: Add Ralink SoCs timer
clocksource/drivers/hyper-v: Rework clocksource and sched clock setup
dt-bindings: timer: brcm,kona-timer: convert to YAML
clocksource/drivers/imx-gpt: Fold <soc/imx/timer.h> into its only user
clk: imx: Drop inclusion of unused header <soc/imx/timer.h>
hrtimer: Add missing sparse annotations to hrtimer locking
clocksource/drivers/imx-gpt: Use only a single name for functions
clocksource/drivers/loongson1: Move PWM timer to clocksource framework
dt-bindings: timer: Add Loongson-1 clocksource
MIPS: Loongson32: Remove deprecated PWM timer clocksource
clocksource/drivers/ingenic-timer: Use pm_sleep_ptr() macro
tracing/timer: Add missing hrtimer modes to decode_hrtimer_mode().
posix-timers: Add sys_ni_posix_timers() prototype
tick/rcu: Fix bogus ratelimit condition
alarmtimer: Remove unnecessary (void *) cast
alarmtimer: Remove unnecessary initialization of variable 'ret'
posix-timers: Refer properly to CONFIG_HIGH_RES_TIMERS
posix-timers: Polish coding style in a few places
posix-timers: Remove pointless comments
...
Sparse warns about lock imbalance vs. the hrtimer_base lock due to missing
sparse annotations:
kernel/time/hrtimer.c:175:33: warning: context imbalance in 'lock_hrtimer_base' - wrong count at exit
kernel/time/hrtimer.c:1301:28: warning: context imbalance in 'hrtimer_start_range_ns' - unexpected unlock
kernel/time/hrtimer.c:1336:28: warning: context imbalance in 'hrtimer_try_to_cancel' - unexpected unlock
kernel/time/hrtimer.c:1457:9: warning: context imbalance in '__hrtimer_get_remaining' - unexpected unlock
Add the annotations to the relevant functions.
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230621075928.394481-1-ben.dooks@codethink.co.uk
The ratelimit logic in report_idle_softirq() is broken because the
exit condition is always true:
static int ratelimit;
if (ratelimit < 10)
return false; ---> always returns here
ratelimit++; ---> no chance to run
Make it check for >= 10 instead.
Fixes: 0345691b24 ("tick/rcu: Stop allowing RCU_SOFTIRQ in idle")
Signed-off-by: Wen Yang <wenyang.linux@foxmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/tencent_5AAA3EEAB42095C9B7740BE62FBF9A67E007@qq.com
Commit c78f261e5dcb ("posix-timers: Clarify posix_timer_fn() comments")
turns an ifdef CONFIG_HIGH_RES_TIMERS into an conditional on
"IS_ENABLED(CONFIG_HIGHRES_TIMERS)"; note that the new conditional refers
to "HIGHRES_TIMERS" not "HIGH_RES_TIMERS" as before.
Fix this typo introduced in that refactoring.
Fixes: c78f261e5dcb ("posix-timers: Clarify posix_timer_fn() comments")
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230609094643.26253-1-lukas.bulwahn@gmail.com
Make the issues vs. SIG_IGN understandable and remove the 15 years old
promise that a proper solution is already on the horizon.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/874jnrdmrq.ffs@tglx
The comment about timer lifetime at the end of the function is misplaced
and uncomprehensible.
Make it understandable and put it at the right place. Add a new comment
about the visibility of the new timer ID to user space.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230425183313.619897296@linutronix.de
The descriptions for common_nsleep() is wrong and common_nsleep_timens()
lacks any form of comment.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230425183313.567072835@linutronix.de
The documentation of sys_clock_settime() permissions is at a random place
and mostly word salad.
Remove it and add a concise comment into sys_clock_settime().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230425183313.514700292@linutronix.de
The decades old comment about Posix clock resolution is confusing at best.
Remove it and add a proper explanation to sys_clock_getres().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230425183313.356427330@linutronix.de
release_posix_timers() is called for cleaning up both hashed and unhashed
timers. The cases are differentiated by an argument and the usage is
hideous.
Seperate the actual free path out and use it for unhashed timers. Provide a
function for hashed timers.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230425183313.301432503@linutronix.de
Jinjie Ruan