From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 7013E6BB52; Wed, 21 Feb 2024 13:20:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708521632; cv=none; b=jg8CcwxeULR8moYd8PcQyeUuYFxbmgLmYkLGYPcN/RH0wtl7fVnBnGDOSvqBdo/j48Z2ock2WXSvipttEoQk0RpR1i1HcjmdEOJdSZ7pRDOKssHqV6SaFRGxrCSVB2r3zrSJ9DDvDtylu4Wzi4w70kE1X6W+SCp0g9Mgta7n3tM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708521632; c=relaxed/simple; bh=eeo7VjluBpS2KcCid9l/OXkFGngYKJOW33nrUYm/m3A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sLtDsT8VJhal9Vzkv8GGbsaoTKZsDc2GKOlJo/NWOAjhRc4XL6ami0ZH3dZM/G6K3BzwJtXNRqa32XyazzElUangZzgskGUCwLoq8GLZzZojxRY+NfBDgyTTr9GAG2P03LOKZAfXnjE2NrV5an790KxQvmOPQUcaM+zCVpCUKmo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=XYINneWe; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="XYINneWe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC99AC433F1; Wed, 21 Feb 2024 13:20:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1708521632; bh=eeo7VjluBpS2KcCid9l/OXkFGngYKJOW33nrUYm/m3A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XYINneWeeGUGsCLqACS+LY/6NSYJhkza3klcyM5759y7zyBrNAp+ZPq/mh1PlwWnS Mf3i+2S31sB/T48hN8w/+AvuYmuNlFwZRwboMO7MrGr7EkAz1U3jOk3mwTTRhnFvkJ qd7ZgbU4pE8OGKhQmrKhmuB4omb8g9i40CuPbAZ8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Paul E. McKenney" , Frederic Weisbecker , Thomas Gleixner Subject: [PATCH 4.19 164/202] hrtimer: Report offline hrtimer enqueue Date: Wed, 21 Feb 2024 14:07:45 +0100 Message-ID: <20240221125937.037456245@linuxfoundation.org> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240221125931.742034354@linuxfoundation.org> References: <20240221125931.742034354@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Frederic Weisbecker commit dad6a09f3148257ac1773cd90934d721d68ab595 upstream. The hrtimers migration on CPU-down hotplug process has been moved earlier, before the CPU actually goes to die. This leaves a small window of opportunity to queue an hrtimer in a blind spot, leaving it ignored. For example a practical case has been reported with RCU waking up a SCHED_FIFO task right before the CPUHP_AP_IDLE_DEAD stage, queuing that way a sched/rt timer to the local offline CPU. Make sure such situations never go unnoticed and warn when that happens. Fixes: 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier") Reported-by: Paul E. McKenney Signed-off-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240129235646.3171983-4-boqun.feng@gmail.com Signed-off-by: Greg Kroah-Hartman --- include/linux/hrtimer.h | 4 +++- kernel/time/hrtimer.c | 3 +++ 2 files changed, 6 insertions(+), 1 deletion(-) --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -182,6 +182,7 @@ enum hrtimer_base_type { * @hang_detected: The last hrtimer interrupt detected a hang * @softirq_activated: displays, if the softirq is raised - update of softirq * related settings is not required then. + * @online: CPU is online from an hrtimers point of view * @nr_events: Total number of hrtimer interrupt events * @nr_retries: Total number of hrtimer interrupt retries * @nr_hangs: Total number of hrtimer interrupt hangs @@ -206,7 +207,8 @@ struct hrtimer_cpu_base { unsigned int hres_active : 1, in_hrtirq : 1, hang_detected : 1, - softirq_activated : 1; + softirq_activated : 1, + online : 1; #ifdef CONFIG_HIGH_RES_TIMERS unsigned int nr_events; unsigned short nr_retries; --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -970,6 +970,7 @@ static int enqueue_hrtimer(struct hrtime enum hrtimer_mode mode) { debug_activate(timer, mode); + WARN_ON_ONCE(!base->cpu_base->online); base->cpu_base->active_bases |= 1 << base->index; @@ -1887,6 +1888,7 @@ int hrtimers_prepare_cpu(unsigned int cp cpu_base->softirq_next_timer = NULL; cpu_base->expires_next = KTIME_MAX; cpu_base->softirq_expires_next = KTIME_MAX; + cpu_base->online = 1; return 0; } @@ -1953,6 +1955,7 @@ int hrtimers_cpu_dying(unsigned int dyin smp_call_function_single(ncpu, retrigger_next_event, NULL, 0); raw_spin_unlock(&new_base->lock); + old_base->online = 0; raw_spin_unlock(&old_base->lock); return 0;