[add stable] On 7/21/08, Oleg Nesterov <[EMAIL PROTECTED]> wrote: > On 07/20, Roland McGrath wrote: >> >> > Yes, thanks, I see. But does it have any meaning for the user-space? >> [si_sys_private] >> >> No, it's not part of the user ABI. It's not even copied out (see >> copy_siginfo_to_user). > > Heh, I didn't know, thanks. > >> > Let me repeat. Can't we make a simple fix for now for this nasty and >> > ancient bug, before we do the more clever changes, >> >> You do need to clear si_overrun there to be correct in the usual case >> (not already queued). > > Indeed, I missed that. Can't we do this in send_sigqueue() ? > >> It would be a perfectly fine and worthwhile optimization/cleanup on its >> own just to move all the initialization of sigq->info (everything but >> si_sys_private) to alloc_posix_timer. > > Yes, we can do this in sys_timer_create(). But this is not very trivial to > do without uglifying the code futher, note this "if (timer_event_spec)". > And we can't do this after "->it_process = process", the timer is already > visible to sys_timer_settime(). > >> Even if it's a fine stopgap, I'm not comfortable calling this a real >> "fix". >> ... >> I don't find it easy to be sure there aren't more bad >> problems caused by trying to re-send the same sigqueue entry. > > Yes, yes, I agree. I propose this change as a first step only. > >> It seems likely this is the good choice for the stable branch. > > So, what do you and Mark think about the patch below? > >> > The thread which does dequeue_signal() continues and re-schedules the >> > timer while ->sigq is queued. Then it copies sigq->info to the user >> > space. >> >> The thread that dequeued the first timer signal had ceased all reference >> to sigq by the time it unlocked siglock. When its do_schedule_next_timer >> call gets it_lock, it can do bookkeeping in struct k_itimer to figure out >> what posix_timer_event or timer_settime has done lately. > > Yes, this should work. > > Oleg. > > --- a/kernel/posix-timers.c > +++ b/kernel/posix-timers.c > @@ -298,12 +298,10 @@ void do_schedule_next_timer(struct sigin > > int posix_timer_event(struct k_itimer *timr,int si_private) > { > - memset(&timr->sigq->info, 0, sizeof(siginfo_t)); > timr->sigq->info.si_sys_private = si_private; > /* Send signal to the process that owns this timer.*/ > > timr->sigq->info.si_signo = timr->it_sigev_signo; > - timr->sigq->info.si_errno = 0; > timr->sigq->info.si_code = SI_TIMER; > timr->sigq->info.si_tid = timr->it_id; > timr->sigq->info.si_value = timr->it_sigev_value; > @@ -435,6 +433,7 @@ static struct k_itimer * alloc_posix_tim > kmem_cache_free(posix_timers_cache, tmr); > tmr = NULL; > } > + memset(&tmr->sigq->info, 0, sizeof(siginfo_t)); > return tmr; > } > > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -1310,6 +1310,7 @@ int send_sigqueue(struct sigqueue *q, st > q->info.si_overrun++; > goto out; > } > + q->info.si_overrun = 0; > > signalfd_notify(t, sig); > pending = group ? &t->signal->shared_pending : &t->pending; > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [EMAIL PROTECTED] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
-- Thanks, Oliver -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html