From nobody Mon Nov 25 02:46:21 2024 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 1AB4E1A705B for ; Thu, 31 Oct 2024 15:46:30 +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=1730389593; cv=none; b=ir8sxukEiHlPZsJAZ2FGZbMZF+2m83SNXRROtTC2iolrte6cb/2h8XjTLaO36RLYozCVCHec4Fuw0zm2mhENNGQ8Myijj39vye5iQCB85sOwpjWsvH2EbochT1IVBnaxEWob2XCDD2XksqlCulKacU9NqSQbkd+HyHEVdwfnzMY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730389593; c=relaxed/simple; bh=Nemrgu/YkY5r3VRndYM1Ns/N5tWy7kTgo331RhnJT6Q=; h=Message-ID:From:To:Cc:Subject:References:MIME-Version: Content-Type:Date; b=lIZBDWvqiLSSzmkkYVMMxBagsPeTgkXS2DDLFlXEkR0caJJTaVOPhtsddVNVUxz8p/E2h1o1yFCiwSGx8oXH32qRgSJlTGCq16Lr+bt0pr/9dofgk8ttEPhHQsIMOoVQCxTkdHnoe9EhzvoadML2L8sNznOaeiieGoKGnP1xjak= 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=2gzUTyKN; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=/hpymbeV; 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="2gzUTyKN"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="/hpymbeV" Message-ID: <20241031154424.867133269@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1730389589; 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=tEeFEzPNCwUi0JRaFaQ+6R6rL1sCe1K+XB0ECNCbAZY=; b=2gzUTyKNZIUhQMFVB+ANPvo0etkCBNlEVUNG6BRRNs3uELn7LoevSu5MRkJkOdBQzKAu42 3Syt2+hk/NWiKxBOhzEAluOHzhDkwzbiUXEN7TZmhtMDf+FsQ1YmhPVW1Gqu60ru5tDbsq 9rZ8LKDRS8QHFZxmwMKd52dMaGqEtwsIpO5Bf34yF9TuCg/1/JZ/zk1aMApqb+EFQKCEwL aDaVtJaT1+6RpUcfils2TFTl11swb+nsrvI9K9/DGloF6j+evRG1oD2CgVUzUD3avp3xdz jqhSEwFZ6z63pNWYHWaaCTRs52Ks6Ivblmp4JnbJQO3GioO9gTWOgczDWo9F6w== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1730389589; 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=tEeFEzPNCwUi0JRaFaQ+6R6rL1sCe1K+XB0ECNCbAZY=; b=/hpymbeVfN8KiKopaj3A/GydAiutDOCzNhn+jCkM6P/00wbQyjPKgxsLtTzkKPi0fl2/LG /YNKw5d6pYAp8eAA== 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 v6 05/20] posix-timers: Add a refcount to struct k_itimer References: <20241031151625.361697424@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Thu, 31 Oct 2024 16:46:29 +0100 (CET) Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" To cure the SIG_IGN handling for posix interval timers, the preallocated sigqueue needs to be embedded into struct k_itimer to prevent life time races of all sorts. To make that work correctly it needs reference counting so that timer deletion does not free the timer prematuraly when there is a signal queued or delivered concurrently. Add a rcuref to the posix timer part. Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Acked-by: Peter Zijlstra (Intel) --- include/linux/posix-timers.h | 14 ++++++++++++++ kernel/time/posix-timers.c | 7 ++++--- 2 files changed, 18 insertions(+), 3 deletions(-) --- --- a/include/linux/posix-timers.h +++ b/include/linux/posix-timers.h @@ -6,11 +6,13 @@ #include #include #include +#include #include #include =20 struct kernel_siginfo; struct task_struct; +struct k_itimer; =20 static inline clockid_t make_process_cpuclock(const unsigned int pid, const clockid_t clock) @@ -105,6 +107,7 @@ static inline void posix_cputimers_rt_wa =20 void posixtimer_rearm_itimer(struct task_struct *p); bool posixtimer_deliver_signal(struct kernel_siginfo *info); +void posixtimer_free_timer(struct k_itimer *timer); =20 /* Init task static initializer */ #define INIT_CPU_TIMERBASE(b) { \ @@ -129,6 +132,7 @@ static inline void posix_cputimers_group u64 cpu_limit) { } static inline void posixtimer_rearm_itimer(struct task_struct *p) { } static inline bool posixtimer_deliver_signal(struct kernel_siginfo *info) = { return false; } +static inline void posixtimer_free_timer(struct k_itimer *timer) { } #endif =20 #ifdef CONFIG_POSIX_CPU_TIMERS_TASK_WORK @@ -156,6 +160,7 @@ static inline void posix_cputimers_init_ * @it_signal: Pointer to the creators signal struct * @it_pid: The pid of the process/task targeted by the signal * @it_process: The task to wakeup on clock_nanosleep (CPU timers) + * @rcuref: Reference count for life time management * @sigq: Pointer to preallocated sigqueue * @it: Union representing the various posix timer type * internals. @@ -180,6 +185,7 @@ struct k_itimer { struct task_struct *it_process; }; struct sigqueue *sigq; + rcuref_t rcuref; union { struct { struct hrtimer timer; @@ -200,4 +206,12 @@ void set_process_cpu_timer(struct task_s =20 int update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new); =20 +#ifdef CONFIG_POSIX_TIMERS +static inline void posixtimer_putref(struct k_itimer *tmr) +{ + if (rcuref_put(&tmr->rcuref)) + posixtimer_free_timer(tmr); +} +#endif /* !CONFIG_POSIX_TIMERS */ + #endif --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -417,10 +417,11 @@ static struct k_itimer * alloc_posix_tim return NULL; } clear_siginfo(&tmr->sigq->info); + rcuref_init(&tmr->rcuref, 1); return tmr; } =20 -static void posix_timer_free(struct k_itimer *tmr) +void posixtimer_free_timer(struct k_itimer *tmr) { put_pid(tmr->it_pid); sigqueue_free(tmr->sigq); @@ -432,7 +433,7 @@ static void posix_timer_unhash_and_free( spin_lock(&hash_lock); hlist_del_rcu(&tmr->t_hash); spin_unlock(&hash_lock); - posix_timer_free(tmr); + posixtimer_putref(tmr); } =20 static int common_timer_create(struct k_itimer *new_timer) @@ -467,7 +468,7 @@ static int do_timer_create(clockid_t whi */ new_timer_id =3D posix_timer_add(new_timer); if (new_timer_id < 0) { - posix_timer_free(new_timer); + posixtimer_free_timer(new_timer); return new_timer_id; }