On Mon, 2013-04-29 at 01:06 -0400, KOSAKI Motohiro wrote: > (4/27/13 12:40 AM), Olivier Langlois wrote: > > > > > > Forbids the cputimer to drift ahead of its process clock by > > blocking its update when a tick occurs while a autoreaping task > > is currently in do_exit() between the call to release_task() and > > its final call to schedule(). > > > > Any task stats update after having called release_task() will > > be lost because they are added to the global process stats located > > in the signal struct from release_task(). > > > > Ideally, you should postpone the release_task() call after the > > final context switch to get all the stats added but this is > > more complex to achieve. > > > > In other words, this is slowing down the cputimer so it keep the same > > pace than the process clock but in fact, what should be done is to > > speed up the process clock by adding the missing stats to it. > > > > Signed-off-by: Olivier Langlois <oliv...@trillion01.com> > > --- > > kernel/sched/fair.c | 10 +++++++++- > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index 7a33e59..52d7b10 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -708,7 +708,15 @@ static void update_curr(struct cfs_rq *cfs_rq) > > > > trace_sched_stat_runtime(curtask, delta_exec, > > curr->vruntime); > > cpuacct_charge(curtask, delta_exec); > > - account_group_exec_runtime(curtask, delta_exec); > > + /* > > + * Do not update the cputimer if the task is already > > released by > > + * release_task(). > > + * > > + * it would preferable to defer the autoreap release_task > > + * after the last context switch but harder to do. > > + */ > > + if (likely(curtask->sighand)) > > + account_group_exec_runtime(curtask, delta_exec); > > } > > I'm confused. glibc's rt/tst-cputimer1 doesn't have thread exiting code. I > have > no seen any issue in this accounting.
glibc launch a helper thread to receive timer signal and will also create a new thread upon signal reception when a timer is created with sigev_notify = SIGEV_THREAD; please see: glibc-2.17/nptl/sysdeps/unix/sysv/linux/timer_create.c glibc-2.17/nptl/sysdeps/unix/sysv/linux/timer_routines.c Greetings, Olivier -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
