From nobody Fri Dec 19 21:46:42 2025 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B1D2D156F2A for ; Mon, 10 Jun 2024 16:42:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718037769; cv=none; b=MIpUOZ93nbMTNeOsGoDo3UsLaSlQ54WXcNuEBMAqhWWPH5tqRm2cvBFGgq2NPsRGveYYd6DRFUzm2vllQy5BWP/LJHP0csvZb0+46D4GBifL4JvEQ3SRBceQSJ5Oxb2Z+XRRzWCMvVaey44BZFTHCTp5g0wPoHQN+tyjeTcUp+s= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718037769; c=relaxed/simple; bh=AEiar334sfqpOjIgW/6Bp180YytMBQoPwW2maP7uYRs=; h=Message-ID:From:To:Cc:Subject:References:MIME-Version: Content-Type:Date; b=XPv72cbyovHKH3ATg8QfwbZklByunQRArVN6iVDHHx/Ggkr8n+G9AwFowisGUj2IqmAZqIlysc9uI9UVjMN3rAsxz6g0EDFHU1Nx2z1sFqSaZCtdmB+cvy5xtvB84qreLzK3cv/yCQv1SjZMoftVESyMG7NnkKGaZKPX4d3fcQ0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=bu1HjfrX; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=WUERlVM3; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="bu1HjfrX"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="WUERlVM3" Message-ID: <20240610164027.545410837@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1718037766; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: references:references; bh=Un9A+m4IV/Z9ANmuwoM32FYX2xiyOcqxqSOJRbG47kY=; b=bu1HjfrXis4sL1fG7x1f+zuZv/e3KX08UVv/UNvvqlcI+2jB2+3XR6pj/bjVRUABVP/qYj wQXh6HlMhhGhUy8mbQKSQHHtjI8lVIwEPwWHSqwfL+JigP/DQsbh+aFXnrwEgqsh4Ac6UV 42xWmGxhBNLWmoGKXI7IsuvzHG51KcYXv3//vyX8fusnlNv+TFHEesiWh4sUnKNqgqb9mV Doe2epCaI3xxK+1K2gy4iH1iRUWIR+OV3k8FnNGNcmjGAE+oN5HCnyXYMHJbfXT+YKYqvX IHv1uSZzV0Z92c8E+EBzqZAsgcbr6gpFEvZj39Bkd8C/T89zrMucchvqKEJ4sg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1718037766; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: references:references; bh=Un9A+m4IV/Z9ANmuwoM32FYX2xiyOcqxqSOJRbG47kY=; b=WUERlVM371nWs6vu8U9MLZkizSJhwgOGCEY5WWrQ4kseFtRO7T4fKPnDVphjTl81paFs9W KnqlzPKx6FJX7KDQ== From: Thomas Gleixner To: LKML Cc: Anna-Maria Behnsen , Frederic Weisbecker , John Stultz , Peter Zijlstra , Ingo Molnar , Stephen Boyd , Eric Biederman , Oleg Nesterov Subject: [patch V3 33/51] posix-timers: Make signal delivery consistent References: <20240610163452.591699700@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Mon, 10 Jun 2024 18:42:46 +0200 (CEST) Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Signals of timers which are reprogammed, disarmed or deleted can deliver signals related to the past. The POSIX spec is blury about this: - "The effect of disarming or resetting a timer with pending expiration notifications is unspecified." - "The disposition of pending signals for the deleted timer is unspecified." In both cases it is reasonable to expect that pending signals are discarded. Especially in the reprogramming case it does not make sense to account for previous overruns or to deliver a signal for a timer which has been disarmed. This makes the behaviour consistent and understandable. Remove the si_sys_private check from the signal delivery code and invoke posix_timer_deliver_signal() unconditionally. Change that function so it controls the actual signal delivery via the return value. It now instructs the signal code to drop the signal when: 1) The timer does not longer exist in the hash table 2) The timer signal_seq value is not the same as the si_sys_private value which was set when the signal was queued. Signed-off-by: Thomas Gleixner --- include/linux/posix-timers.h | 2 -- kernel/signal.c | 2 +- kernel/time/posix-cpu-timers.c | 2 +- kernel/time/posix-timers.c | 25 +++++++++++++++---------- 4 files changed, 17 insertions(+), 14 deletions(-) --- a/include/linux/posix-timers.h +++ b/include/linux/posix-timers.h @@ -137,8 +137,6 @@ static inline void clear_posix_cputimers static inline void posix_cputimers_init_work(void) { } #endif =20 -#define REQUEUE_PENDING 1 - /** * struct k_itimer - POSIX.1b interval timer structure. * @list: List head for binding the timer to signals->posix_timers --- a/kernel/signal.c +++ b/kernel/signal.c @@ -617,7 +617,7 @@ int dequeue_signal(sigset_t *mask, kerne } =20 if (IS_ENABLED(CONFIG_POSIX_TIMERS)) { - if (unlikely(info->si_code =3D=3D SI_TIMER && info->si_sys_private)) { + if (unlikely(info->si_code =3D=3D SI_TIMER)) { if (!posixtimer_deliver_signal(info)) goto again; } --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -746,7 +746,7 @@ static void __posix_cpu_timer_get(struct * - Timers which expired, but the signal has not yet been * delivered */ - if (iv && ((timer->it_signal_seq & REQUEUE_PENDING) || sigev_none)) + if (iv && timer->it_status !=3D POSIX_TIMER_ARMED) expires =3D bump_cpu_timer(timer, now); else expires =3D cpu_timer_getexpires(&timer->it.cpu); --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -269,7 +269,10 @@ bool posixtimer_deliver_signal(struct ke if (!timr) goto out; =20 - if (timr->it_interval && timr->it_signal_seq =3D=3D info->si_sys_private)= { + if (timr->it_signal_seq !=3D info->si_sys_private) + goto out_unlock; + + if (timr->it_interval && timr->it_status =3D=3D POSIX_TIMER_REQUEUE_PENDI= NG) { timr->kclock->timer_rearm(timr); =20 timr->it_status =3D POSIX_TIMER_ARMED; @@ -281,6 +284,7 @@ bool posixtimer_deliver_signal(struct ke } ret =3D true; =20 +out_unlock: unlock_timer(timr, flags); out: spin_lock(¤t->sighand->siglock); @@ -293,19 +297,19 @@ bool posixtimer_deliver_signal(struct ke int posix_timer_queue_signal(struct k_itimer *timr) { enum posix_timer_state state =3D POSIX_TIMER_DISARMED; - int ret, si_private =3D 0; enum pid_type type; + int ret; =20 lockdep_assert_held(&timr->it_lock); =20 if (timr->it_interval) { + timr->it_signal_seq++; state =3D POSIX_TIMER_REQUEUE_PENDING; - si_private =3D ++timr->it_signal_seq; } timr->it_status =3D state; =20 type =3D !(timr->it_sigev_notify & SIGEV_THREAD_ID) ? PIDTYPE_TGID : PIDT= YPE_PID; - ret =3D send_sigqueue(timr->sigq, timr->it_pid, type, si_private); + ret =3D send_sigqueue(timr->sigq, timr->it_pid, type, timr->it_signal_seq= ); /* If we failed to send the signal the timer stops. */ return ret > 0; } @@ -670,7 +674,7 @@ void common_timer_get(struct k_itimer *t * is a SIGEV_NONE timer move the expiry time forward by intervals, * so expiry is > now. */ - if (iv && (timr->it_signal_seq & REQUEUE_PENDING || sig_none)) + if (iv && timr->it_status !=3D POSIX_TIMER_ARMED) timr->it_overrun +=3D kc->timer_forward(timr, now); =20 remaining =3D kc->timer_remaining(timr, now); @@ -870,8 +874,6 @@ void posix_timer_set_common(struct k_iti else timer->it_interval =3D 0; =20 - /* Prevent reloading in case there is a signal pending */ - timer->it_signal_seq =3D (timer->it_signal_seq + 2) & ~REQUEUE_PENDING; /* Reset overrun accounting */ timer->it_overrun_last =3D 0; timer->it_overrun =3D -1LL; @@ -889,8 +891,6 @@ int common_timer_set(struct k_itimer *ti if (old_setting) common_timer_get(timr, old_setting); =20 - /* Prevent rearming by clearing the interval */ - timr->it_interval =3D 0; /* * Careful here. On SMP systems the timer expiry function could be * active and spinning on timr->it_lock. @@ -940,6 +940,9 @@ static int do_timer_settime(timer_t time if (old_spec64) old_spec64->it_interval =3D ktime_to_timespec64(timr->it_interval); =20 + /* Prevent signal delivery and rearming. */ + timr->it_signal_seq++; + kc =3D timr->kclock; if (WARN_ON_ONCE(!kc || !kc->timer_set)) error =3D -EINVAL; @@ -1008,7 +1011,6 @@ int common_timer_del(struct k_itimer *ti { const struct k_clock *kc =3D timer->kclock; =20 - timer->it_interval =3D 0; if (kc->timer_try_to_cancel(timer) < 0) return TIMER_RETRY; timer->it_status =3D POSIX_TIMER_DISARMED; @@ -1036,6 +1038,9 @@ SYSCALL_DEFINE1(timer_delete, timer_t, t if (!timer) return -EINVAL; =20 + /* Prevent signal delivery and rearming. */ + timer->it_signal_seq++; + if (unlikely(timer_delete_hook(timer) =3D=3D TIMER_RETRY)) { /* Unlocks and relocks the timer if it still exists */ timer =3D timer_wait_running(timer, &flags);