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cputime: Safely read cputime of full dynticks CPUs

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While remotely reading the cputime of a task running in a
full dynticks CPU, the values stored in utime/stime fields
of struct task_struct may be stale. Its values may be those
of the last kernel <-> user transition time snapshot and
we need to add the tickless time spent since this snapshot.

To fix this, flush the cputime of the dynticks CPUs on
kernel <-> user transition and record the time / context
where we did this. Then on top of this snapshot and the current
time, perform the fixup on the reader side from task_times()
accessors.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
[fixed kvm module related build errors]
Signed-off-by: Sedat Dilek <sedat.dilek@gmail.com>
This commit is contained in:
Frederic Weisbecker 2012-12-16 20:00:34 +01:00
commit 6a61671bb2
11 changed files with 292 additions and 54 deletions
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27
include/linux/sched.h
View file

@ -1367,6 +1367,15 @@ struct task_struct {
cputime_t gtime;
#ifndef CONFIG_VIRT_CPU_ACCOUNTING
struct cputime prev_cputime;
#endif
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
seqlock_t vtime_seqlock;
unsigned long long vtime_snap;
enum {
VTIME_SLEEPING = 0,
VTIME_USER,
VTIME_SYS,
} vtime_snap_whence;
#endif
unsigned long nvcsw, nivcsw; /* context switch counts */
struct timespec start_time; /* monotonic time */
@ -1792,11 +1801,13 @@ static inline void put_task_struct(struct task_struct *t)
__put_task_struct(t);
}
static inline cputime_t task_gtime(struct task_struct *t)
{
return t->gtime;
}
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
extern void task_cputime(struct task_struct *t,
cputime_t *utime, cputime_t *stime);
extern void task_cputime_scaled(struct task_struct *t,
cputime_t *utimescaled, cputime_t *stimescaled);
extern cputime_t task_gtime(struct task_struct *t);
#else
static inline void task_cputime(struct task_struct *t,
cputime_t *utime, cputime_t *stime)
{
@ -1815,6 +1826,12 @@ static inline void task_cputime_scaled(struct task_struct *t,
if (stimescaled)
*stimescaled = t->stimescaled;
}
static inline cputime_t task_gtime(struct task_struct *t)
{
return t->gtime;
}
#endif
extern void task_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st);
extern void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st);