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Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull scheduler fixes from Ingo Molnar:
 "Two cputime fixes - hopefully the last ones"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/cputime: Resync steal time when guest & host lose sync
  sched/cputime: Fix NO_HZ_FULL getrusage() monotonicity regression
This commit is contained in:
Linus Torvalds 2016-08-18 15:07:21 -07:00
parent 0dcb7b6f8f 03cbc73263
commit ac78bc714b
1 changed files with 25 additions and 8 deletions
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33
kernel/sched/cputime.c
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@ -263,6 +263,11 @@ void account_idle_time(cputime_t cputime)
cpustat[CPUTIME_IDLE] += (__force u64) cputime;
}
/*
* When a guest is interrupted for a longer amount of time, missed clock
* ticks are not redelivered later. Due to that, this function may on
* occasion account more time than the calling functions think elapsed.
*/
static __always_inline cputime_t steal_account_process_time(cputime_t maxtime)
{
#ifdef CONFIG_PARAVIRT
@ -371,7 +376,7 @@ static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
* idle, or potentially user or system time. Due to rounding,
* other time can exceed ticks occasionally.
*/
other = account_other_time(cputime);
other = account_other_time(ULONG_MAX);
if (other >= cputime)
return;
cputime -= other;
@ -486,7 +491,7 @@ void account_process_tick(struct task_struct *p, int user_tick)
}
cputime = cputime_one_jiffy;
steal = steal_account_process_time(cputime);
steal = steal_account_process_time(ULONG_MAX);
if (steal >= cputime)
return;
@ -516,7 +521,7 @@ void account_idle_ticks(unsigned long ticks)
}
cputime = jiffies_to_cputime(ticks);
steal = steal_account_process_time(cputime);
steal = steal_account_process_time(ULONG_MAX);
if (steal >= cputime)
return;
@ -614,19 +619,25 @@ static void cputime_adjust(struct task_cputime *curr,
stime = curr->stime;
utime = curr->utime;
if (utime == 0) {
stime = rtime;
/*
* If either stime or both stime and utime are 0, assume all runtime is
* userspace. Once a task gets some ticks, the monotonicy code at
* 'update' will ensure things converge to the observed ratio.
*/
if (stime == 0) {
utime = rtime;
goto update;
}
if (stime == 0) {
utime = rtime;
if (utime == 0) {
stime = rtime;
goto update;
}
stime = scale_stime((__force u64)stime, (__force u64)rtime,
(__force u64)(stime + utime));
update:
/*
* Make sure stime doesn't go backwards; this preserves monotonicity
* for utime because rtime is monotonic.
@ -649,7 +660,6 @@ static void cputime_adjust(struct task_cputime *curr,
stime = rtime - utime;
}
update:
prev->stime = stime;
prev->utime = utime;
out:
@ -694,6 +704,13 @@ static cputime_t get_vtime_delta(struct task_struct *tsk)
unsigned long now = READ_ONCE(jiffies);
cputime_t delta, other;
/*
* Unlike tick based timing, vtime based timing never has lost
* ticks, and no need for steal time accounting to make up for
* lost ticks. Vtime accounts a rounded version of actual
* elapsed time. Limit account_other_time to prevent rounding
* errors from causing elapsed vtime to go negative.
*/
delta = jiffies_to_cputime(now - tsk->vtime_snap);
other = account_other_time(delta);
WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_INACTIVE);