On Mon, May 06, 2013 at 11:35:50PM -0400, Olivier Langlois wrote: > Frederic, > > On Tue, 2013-05-07 at 01:18 +0200, Frederic Weisbecker wrote: > > On Mon, Apr 29, 2013 at 02:04:09PM -0400, 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(). > > > > I wonder if this is real problem that the clock is ahead of the timer. > > Have you seen any issue in practice with this? > > note that it is the timer that will be ahead because the process clock > is the sum of past group tasks exec time plus current group tasks exec > time. Few updates are missing in the past group tasks exec time counter > in struct signal. > > The effect of this is failure of the unittest testing POSIX compliance > in glibc rt/tst-cputimer1.c > > pseudo code of the test is: > > 1. call clock_gettime() to get now > 2. Compute timer expiring time now+timer interval > 3. call clock_gettime() when timer cb is called > 4. Compare that clock_gettime() result is >= than computed expiring time > > The error is adding up as more thread exits and usually the test fails > when testing periodic timers where threads are created to handle the > timer timeouts.
I see. Ok if it breaks a glibc test, it seems like a good reason to fix it :) Thanks! -- 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/
