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nohz: Allow 32-bit machines to sleep for more than 2.15 seconds 

In the dynamic tick code, "max_delta_ns" (member of the
"clock_event_device" structure) represents the maximum sleep time
that can occur between timer events in nanoseconds.

The variable, "max_delta_ns", is defined as an unsigned long
which is a 32-bit integer for 32-bit machines and a 64-bit
integer for 64-bit machines (if -m64 option is used for gcc).
The value of max_delta_ns is set by calling the function
"clockevent_delta2ns()" which returns a maximum value of LONG_MAX.
For a 32-bit machine LONG_MAX is equal to 0x7fffffff and in
nanoseconds this equates to ~2.15 seconds. Hence, the maximum
sleep time for a 32-bit machine is ~2.15 seconds, where as for
a 64-bit machine it will be many years.

This patch changes the type of max_delta_ns to be "u64" instead of
"unsigned long" so that this variable is a 64-bit type for both 32-bit
and 64-bit machines. It also changes the maximum value returned by
clockevent_delta2ns() to KTIME_MAX.  Hence this allows a 32-bit
machine to sleep for longer than ~2.15 seconds. Please note that this
patch also changes "min_delta_ns" to be "u64" too and although this is
unnecessary, it makes the patch simpler as it avoids to fixup all
callers of clockevent_delta2ns().

[ tglx: changed "unsigned long long" to u64 as we use this data type
  	through out the time code ]

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Cc: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <1250617512-23567-3-git-send-email-jon-hunter@ti.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Jon Hunter 2009-08-18 12:45:11 -05:00 committed by Thomas Gleixner
parent 27185016b8
commit 97813f2fe7
5 changed files with 17 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/clockchips.h
View File

@ -77,8 +77,8 @@ enum clock_event_nofitiers {
struct clock_event_device {
const char *name;
unsigned int features;
unsigned long max_delta_ns;
unsigned long min_delta_ns;
u64 max_delta_ns;
u64 min_delta_ns;
u32 mult;
u32 shift;
int rating;
@ -116,8 +116,8 @@ static inline unsigned long div_sc(unsigned long ticks, unsigned long nsec,
}
/* Clock event layer functions */
extern unsigned long clockevent_delta2ns(unsigned long latch,
struct clock_event_device *evt);
extern u64 clockevent_delta2ns(unsigned long latch,
struct clock_event_device *evt);
extern void clockevents_register_device(struct clock_event_device *dev);
extern void clockevents_exchange_device(struct clock_event_device *old,

3
kernel/hrtimer.c
View File

@ -1240,7 +1240,8 @@ hrtimer_interrupt_hanging(struct clock_event_device *dev,
force_clock_reprogram = 1;
dev->min_delta_ns = (unsigned long)try_time.tv64 * 3;
printk(KERN_WARNING "hrtimer: interrupt too slow, "
"forcing clock min delta to %lu ns\n", dev->min_delta_ns);
"forcing clock min delta to %llu ns\n",
(unsigned long long) dev->min_delta_ns);
}
/*
* High resolution timer interrupt

11
kernel/time/clockevents.c
View File

@ -37,10 +37,9 @@ static DEFINE_SPINLOCK(clockevents_lock);
*
* Math helper, returns latch value converted to nanoseconds (bound checked)
*/
unsigned long clockevent_delta2ns(unsigned long latch,
struct clock_event_device *evt)
u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
{
u64 clc = ((u64) latch << evt->shift);
u64 clc = (u64) latch << evt->shift;
if (unlikely(!evt->mult)) {
evt->mult = 1;
@ -50,10 +49,10 @@ unsigned long clockevent_delta2ns(unsigned long latch,
do_div(clc, evt->mult);
if (clc < 1000)
clc = 1000;
if (clc > LONG_MAX)
clc = LONG_MAX;
if (clc > KTIME_MAX)
clc = KTIME_MAX;
return (unsigned long) clc;
return clc;
}
EXPORT_SYMBOL_GPL(clockevent_delta2ns);

4
kernel/time/tick-oneshot.c
View File

@ -50,9 +50,9 @@ int tick_dev_program_event(struct clock_event_device *dev, ktime_t expires,
dev->min_delta_ns += dev->min_delta_ns >> 1;
printk(KERN_WARNING
"CE: %s increasing min_delta_ns to %lu nsec\n",
"CE: %s increasing min_delta_ns to %llu nsec\n",
dev->name ? dev->name : "?",
dev->min_delta_ns << 1);
(unsigned long long) dev->min_delta_ns << 1);
i = 0;
}

6
kernel/time/timer_list.c
View File

@ -204,8 +204,10 @@ print_tickdevice(struct seq_file *m, struct tick_device *td, int cpu)
return;
}
SEQ_printf(m, "%s\n", dev->name);
SEQ_printf(m, " max_delta_ns: %lu\n", dev->max_delta_ns);
SEQ_printf(m, " min_delta_ns: %lu\n", dev->min_delta_ns);
SEQ_printf(m, " max_delta_ns: %llu\n",
(unsigned long long) dev->max_delta_ns);
SEQ_printf(m, " min_delta_ns: %llu\n",
(unsigned long long) dev->min_delta_ns);
SEQ_printf(m, " mult: %u\n", dev->mult);
SEQ_printf(m, " shift: %u\n", dev->shift);
SEQ_printf(m, " mode: %d\n", dev->mode);