On Mon, 2013-04-29 at 15:09 -0400, KOSAKI Motohiro wrote: > (4/29/13 2:54 PM), Olivier Langlois wrote: > > On Mon, 2013-04-29 at 14:31 -0400, KOSAKI Motohiro wrote: > >> (4/29/13 2:20 PM), Olivier Langlois wrote: > >>> > >>>> > >>>>>> 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 > >>>> > >>>> I know. I taled thread exiting. not thread creating. And, as far as I > >>>> can see, only test sig1 can fail, > >>>> not thr[12]. > >>>> > >>> Apart from glibc helper thread, the threads created for handling timer > >>> firing all do exit immediatly as soon as user callback returns. > >> > >> And, libc ensure its exiting finished before starting actual tests. Why > >> such thread exiting > >> affect timers code? It shouldn't. becuase signal.cputimer is initialized > >> timer_settime(). > >> The initialization is incorrect, we should fix initialization. > > > > It doesn't have anything to do with initialisation. > > > > Quick Quiz #1: How does the cputimer tick? > > Answer: With calls to account_group_exec_runtime() > > Only account when cputimer->running. Quick Quiz: When turn on > cputimer->running? > > > > Every task updates occuring after release_task() has been called in > > do_exit() (scheduler ticks or the task final schedule() call) will be > > lost because tasks stats are added to the global group stats located in > > the signal struct in release_task() So every update after release_task() > > will be lost but account_group_exec_runtime is still called. > > tick lost doesn't occur an issue. because glibc only test posix conformance > and > posix allow inacculacy. In other words, timer must not run faster than real > clock. > but lost and makes slower are accepted in the test. > What is lost isn't cputimer tick. They are accounted account_group_exec_runtime(). What is lost it is what is added to curr->sum_exec_runtime. Thus making the thread group clock running slower than the cputimer.
Please spend some time reading the code and less time writing e-mails. Read the code of release_task() and where it is called in do_exit(). Once it is done, it should be clear to you. -- 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/
