exit: Always reap resource stats in __exit_signal() (90ed9cbe) · Commits · 戴 / test

Oleg pointed out that wait_task_zombie adds a task's usage statistics to the parent's signal struct, but the task's own signal struct should also propagate the statistics at exit time. This allows thread_group_cputime(reaped_zombie) to get the statistics after __unhash_process() has made the task invisible to for_each_thread, but before the thread has actually been rcu freed, making sure no non-monotonic results are returned inside that window. Suggested-by:

Oleg Nesterov <oleg@redhat.com> Signed-off-by:

Rik van Riel <riel@redhat.com> Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: David Rientjes <rientjes@google.com> Cc: Guillaume Morin <guillaume@morinfr.org> Cc: Ionut Alexa <ionut.m.alexa@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Li Zefan <lizefan@huawei.com> Cc: Michal Hocko <mhocko@suse.cz> Cc: Michal Schmidt <mschmidt@redhat.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: umgwanakikbuti@gmail.com Cc: fweisbec@gmail.com Cc: srao@redhat.com Cc: lwoodman@redhat.com Cc: atheurer@redhat.com Link: http://lkml.kernel.org/r/1408133138-22048-2-git-send-email-riel@redhat.com Signed-off-by:

Ingo Molnar <mingo@kernel.org>

kernel/exit.c

+21 −22

Original line number	Diff line number	Diff line
		@@ -115,15 +115,16 @@ static void __exit_signal(struct task_struct *tsk)

		if (tsk == sig->curr_target)
		sig->curr_target = next_thread(tsk);
		}

		/*
		* Accumulate here the counters for all threads but the
		* group leader as they die, so they can be added into
		* the process-wide totals when those are taken.
		* The group leader stays around as a zombie as long
		* as there are other threads. When it gets reaped,
		* the exit.c code will add its counts into these totals.
		* We won't ever get here for the group leader, since it
		* will have been the last reference on the signal_struct.
		* Accumulate here the counters for all threads but the group leader
		* as they die, so they can be added into the process-wide totals
		* when those are taken. The group leader stays around as a zombie as
		* long as there are other threads. When it gets reaped, the exit.c
		* code will add its counts into these totals. We won't ever get here
		* for the group leader, since it will have been the last reference on
		* the signal_struct.
		*/
		task_cputime(tsk, &utime, &stime);
		sig->utime += utime;
		@@ -137,8 +138,6 @@ static void __exit_signal(struct task_struct *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->nr_threads--;
		__unhash_process(tsk, group_dead);

Admin message