Messages in this thread Patch in this message | | | From | Thomas Gleixner <> | Subject | [patch 29/45] posix-timers: Make signal overrun accounting sensible | Date | Tue, 6 Jun 2023 16:38:04 +0200 (CEST) |
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The handling of the timer overrun in the signal code is inconsistent as it takes previous overruns into account. This is just wrong as after the reprogramming of a timer the overrun count starts over from a clean state, i.e. 0.
Make the accounting in send_sigqueue() consistent with that.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- kernel/signal.c | 34 ++++++++++++++++++++++++++++------ 1 file changed, 28 insertions(+), 6 deletions(-)
--- a/kernel/signal.c +++ b/kernel/signal.c @@ -1957,6 +1957,34 @@ int send_sigqueue(struct sigqueue *q, st */ q->info.si_sys_private = si_private; + /* + * Set the overrun count to zero unconditionally. The posix timer + * code does not self rearm periodic timers. They are rearmed from + * dequeue_signal(). + * + * But there is a situation where @q is already enqueued: + * + * 1) timer_settime() + * arm_timer() + * 2) timer_expires() + * send_sigqueue(@q) + * enqueue(@q) + * 3) timer_settime() + * arm_timer() + * 4) timer_expires() + * send_sigqueue(@q) <- Observes @q already queued + * + * In this case incrementing si_overrun does not make sense because + * there is no relationship between timer_settime() #1 and #2. + * + * The POSIX specification is useful as always: "The effect of + * disarming or resetting a timer with pending expiration + * notifications is unspecified." + * + * Just do the sensible thing and reset the overrun. + */ + q->info.si_overrun = 0; + ret = 1; /* the signal is ignored */ result = TRACE_SIGNAL_IGNORED; if (!prepare_signal(sig, t, false)) @@ -1964,15 +1992,9 @@ int send_sigqueue(struct sigqueue *q, st ret = 0; if (unlikely(!list_empty(&q->list))) { - /* - * If an SI_TIMER entry is already queue just increment - * the overrun count. - */ - q->info.si_overrun++; result = TRACE_SIGNAL_ALREADY_PENDING; goto out; } - q->info.si_overrun = 0; signalfd_notify(t, sig); pending = (type != PIDTYPE_PID) ? &t->signal->shared_pending : &t->pending;
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