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authorFrederic Weisbecker <fweisbec@gmail.com>2012-12-16 14:00:34 -0500
committerFrederic Weisbecker <fweisbec@gmail.com>2013-01-27 14:35:47 -0500
commit6a61671bb2f3a1bd12cd17b8fca811a624782632 (patch)
tree0afc2915fb7e517472710a49a524510322dd5baa /kernel/fork.c
parentc11f11fcbdb5be790c565aed46411486a7586afc (diff)
cputime: Safely read cputime of full dynticks CPUs
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>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 65ca6d27f24e..e68a95b4cf26 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1233,6 +1233,12 @@ static struct task_struct *copy_process(unsigned long clone_flags,
1233#ifndef CONFIG_VIRT_CPU_ACCOUNTING 1233#ifndef CONFIG_VIRT_CPU_ACCOUNTING
1234 p->prev_cputime.utime = p->prev_cputime.stime = 0; 1234 p->prev_cputime.utime = p->prev_cputime.stime = 0;
1235#endif 1235#endif
1236#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1237 seqlock_init(&p->vtime_seqlock);
1238 p->vtime_snap = 0;
1239 p->vtime_snap_whence = VTIME_SLEEPING;
1240#endif
1241
1236#if defined(SPLIT_RSS_COUNTING) 1242#if defined(SPLIT_RSS_COUNTING)
1237 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1243 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1238#endif 1244#endif