Merge branch 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
authorLinus Torvalds <torvalds@linux-foundation.org>
Mon, 11 Aug 2008 23:46:11 +0000 (16:46 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Mon, 11 Aug 2008 23:46:11 +0000 (16:46 -0700)
* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  posix-timers: fix posix_timer_event() vs dequeue_signal() race
  posix-timers: do_schedule_next_timer: fix the setting of ->si_overrun

kernel/posix-timers.c
kernel/signal.c

index 9a21681aa80f82f0123917725f341a526d484c89..e36d5798cbff427fca02fd8c9a8fb6f615dbd3fe 100644 (file)
@@ -289,21 +289,29 @@ void do_schedule_next_timer(struct siginfo *info)
                else
                        schedule_next_timer(timr);
 
-               info->si_overrun = timr->it_overrun_last;
+               info->si_overrun += timr->it_overrun_last;
        }
 
        if (timr)
                unlock_timer(timr, flags);
 }
 
-int posix_timer_event(struct k_itimer *timr,int si_private)
+int posix_timer_event(struct k_itimer *timr, int si_private)
 {
-       memset(&timr->sigq->info, 0, sizeof(siginfo_t));
+       /*
+        * FIXME: if ->sigq is queued we can race with
+        * dequeue_signal()->do_schedule_next_timer().
+        *
+        * If dequeue_signal() sees the "right" value of
+        * si_sys_private it calls do_schedule_next_timer().
+        * We re-queue ->sigq and drop ->it_lock().
+        * do_schedule_next_timer() locks the timer
+        * and re-schedules it while ->sigq is pending.
+        * Not really bad, but not that we want.
+        */
        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 +443,7 @@ static struct k_itimer * alloc_posix_timer(void)
                kmem_cache_free(posix_timers_cache, tmr);
                tmr = NULL;
        }
+       memset(&tmr->sigq->info, 0, sizeof(siginfo_t));
        return tmr;
 }
 
index 954f77d7e3bc2368f405fa2ab83aaf58d6280fb3..c539f60c6f41bc2b9e170b93bf66a8bca5e93ce3 100644 (file)
@@ -1304,6 +1304,7 @@ int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group)
                q->info.si_overrun++;
                goto out;
        }
+       q->info.si_overrun = 0;
 
        signalfd_notify(t, sig);
        pending = group ? &t->signal->shared_pending : &t->pending;