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| author | Frederic Weisbecker <fweisbec@gmail.com> | 2013-07-13 17:10:18 +0200 |
|---|---|---|
| committer | Frederic Weisbecker <fweisbec@gmail.com> | 2013-08-14 17:14:50 +0200 |
| commit | 54461562c90e0ac104764c5a9de637fd9151a1c1 (patch) | |
| tree | df04e7b576eb54a29e80f9827c73d473c87ec0bf /kernel | |
| parent | vtime: Remove a few unneeded generic vtime state checks (diff) | |
| download | linux-54461562c90e0ac104764c5a9de637fd9151a1c1.tar.xz linux-54461562c90e0ac104764c5a9de637fd9151a1c1.zip | |
vtime: Fix racy cputime delta update
get_vtime_delta() must be called under the task vtime_seqlock
with the code that does the cputime accounting flush.
Otherwise the cputime reader can be fooled and run into
a race where it sees the snapshot update but misses the
cputime flush. As a result it can report a cputime that is
way too short.
Fix vtime_account_user() that wasn't complying to that rule.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Kevin Hilman <khilman@linaro.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/cputime.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 5f273b477764..b62d5c027c7e 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -683,9 +683,10 @@ void vtime_account_irq_exit(struct task_struct *tsk) void vtime_account_user(struct task_struct *tsk) { - cputime_t delta_cpu = get_vtime_delta(tsk); + cputime_t delta_cpu; write_seqlock(&tsk->vtime_seqlock); + delta_cpu = get_vtime_delta(tsk); tsk->vtime_snap_whence = VTIME_SYS; account_user_time(tsk, delta_cpu, cputime_to_scaled(delta_cpu)); write_sequnlock(&tsk->vtime_seqlock); |