Messages in this thread | | | Date | Tue, 6 Sep 2016 21:01:29 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v3] sched/cputime: Protect some other sum_exec_runtime reads on 32 bit cpus |
| |
On Tue, Sep 06, 2016 at 02:49:08PM +0200, Stanislaw Gruszka wrote: > diff --git a/kernel/exit.c b/kernel/exit.c > index 2f974ae..a46f96f 100644 > --- a/kernel/exit.c > +++ b/kernel/exit.c > @@ -134,7 +134,7 @@ static void __exit_signal(struct task_struct *tsk) > sig->inblock += task_io_get_inblock(tsk); > sig->oublock += task_io_get_oublock(tsk); > task_io_accounting_add(&sig->ioac, &tsk->ioac); > - sig->sum_sched_runtime += tsk->se.sum_exec_runtime; > + sig->sum_sched_runtime += read_sum_exec_runtime(tsk); > sig->nr_threads--; > __unhash_process(tsk, group_dead); > write_sequnlock(&sig->stats_lock);
If I'm not mistaken, at this point @p is dead, sum_exec_runtime will not ever be updated again.
> diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c > index b93c72d..4d080f2 100644 > --- a/kernel/sched/cputime.c > +++ b/kernel/sched/cputime.c > @@ -702,7 +682,7 @@ out: > void task_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st) > { > struct task_cputime cputime = { > - .sum_exec_runtime = p->se.sum_exec_runtime, > + .sum_exec_runtime = read_sum_exec_runtime(p), > }; > > task_cputime(p, &cputime.utime, &cputime.stime);
Right, even if @p == current, this can race with an interrupt (the tick) updating sum_exec_runtime.
> diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c > index 39008d7..a2d753b 100644 > --- a/kernel/time/posix-cpu-timers.c > +++ b/kernel/time/posix-cpu-timers.c > @@ -848,7 +848,7 @@ static void check_thread_timers(struct task_struct *tsk, > tsk_expires->virt_exp = expires_to_cputime(expires); > > tsk_expires->sched_exp = check_timers_list(++timers, firing, > - tsk->se.sum_exec_runtime); > + read_sum_exec_runtime(tsk)); > > /* > * Check for the special case thread timers.
@tsk == current and IRQs are disabled, sum_exec_runtime cannot be updated.
> @@ -1115,7 +1115,7 @@ static inline int fastpath_timer_check(struct task_struct *tsk) > struct task_cputime task_sample; > > task_cputime(tsk, &task_sample.utime, &task_sample.stime); > - task_sample.sum_exec_runtime = tsk->se.sum_exec_runtime; > + task_sample.sum_exec_runtime = read_sum_exec_runtime(tsk); > if (task_cputime_expired(&task_sample, &tsk->cputime_expires)) > return 1; > }
Same.
| |