Messages in this thread Patch in this message | | | Date | Fri, 7 Nov 2008 17:52:38 +0100 | From | Oleg Nesterov <> | Subject | [PATCH] account_group_exec_runtime: fix the racy usage of ->signal |
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Compile tested.
Unlike other similar routines, account_group_exec_runtime() could be called "implicitly" after exit_notify(). This means we can race with the parent doing release_task(), we can't just check ->signal != NULL.
Take ->siglock to make sure ->signal can't go away.
This is the minimal fix, with this patch we don't need need get/put cpu, and I think we should uninline this function.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
--- K-28/kernel/sched_stats.h~A_G_E_R_FIX 2008-11-07 17:32:02.000000000 +0100 +++ K-28/kernel/sched_stats.h 2008-11-07 17:44:39.000000000 +0100 @@ -351,10 +351,12 @@ static inline void account_group_exec_ru unsigned long long ns) { struct signal_struct *sig; + unsigned long flags; - sig = tsk->signal; - if (unlikely(!sig)) + if (unlikely(!lock_task_sighand(tsk, &flags))) return; + + sig = tsk->signal; if (sig->cputime.totals) { struct task_cputime *times; @@ -362,4 +364,6 @@ static inline void account_group_exec_ru times->sum_exec_runtime += ns; put_cpu_no_resched(); } + + unlock_task_sighand(tsk, &flags); }
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