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PM: s2idle: Clear _TIF_POLLING_NRFLAG before suspend to idle 

Suspend to idle was found to not work on Goldmont CPU recently.

The issue happens due to:

 1. On Goldmont the CPU in idle can only be woken up via IPIs,
    not POLLING mode, due to commit 08e237fa56 ("x86/cpu: Add
    workaround for MONITOR instruction erratum on Goldmont based
    CPUs")

 2. When the CPU is entering suspend to idle process, the
    _TIF_POLLING_NRFLAG remains on, because cpuidle_enter_s2idle()
    doesn't match call_cpuidle() exactly.

 3. Commit b2a02fc43a ("smp: Optimize send_call_function_single_ipi()")
    makes use of _TIF_POLLING_NRFLAG to avoid sending IPIs to idle
    CPUs.

 4. As a result, some IPIs related functions might not work
    well during suspend to idle on Goldmont. For example, one
    suspected victim:

    tick_unfreeze() -> timekeeping_resume() -> hrtimers_resume()
    -> clock_was_set() -> on_each_cpu() might wait forever,
    because the IPIs will not be sent to the CPUs which are
    sleeping with _TIF_POLLING_NRFLAG set, and Goldmont CPU
    could not be woken up by only setting _TIF_NEED_RESCHED
    on the monitor address.

To avoid that, clear the _TIF_POLLING_NRFLAG flag before invoking
enter_s2idle_proper() in cpuidle_enter_s2idle() in analogy with the
call_cpuidle() code flow.

Fixes: b2a02fc43a ("smp: Optimize send_call_function_single_ipi()")
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
[ rjw: Subject / changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Chen Yu 2020-06-23 14:31:31 +08:00 committed by Rafael J. Wysocki
parent 48778464bb
commit 81e6737518
1 changed files with 2 additions and 1 deletions
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3
drivers/cpuidle/cpuidle.c
View File

@ -13,6 +13,7 @@
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/sched/clock.h>
#include <linux/sched/idle.h>
#include <linux/notifier.h>
#include <linux/pm_qos.h>
#include <linux/cpu.h>
@ -186,7 +187,7 @@ int cpuidle_enter_s2idle(struct cpuidle_driver *drv, struct cpuidle_device *dev)
* be frozen safely.
*/
index = find_deepest_state(drv, dev, U64_MAX, 0, true);
if (index > 0)
if (index > 0 && !current_clr_polling_and_test())
enter_s2idle_proper(drv, dev, index);
return index;