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 68ABF69D3B; Wed, 21 Feb 2024 13:44:49 +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=1708523089; cv=none; b=lItplurti/9lhqBurVYt33oyJjjcl+Twp3rIC8AKTgQhLtFN9nrmllZBHq1hGTtvYvQfdr4JPRo/uB4ckV9KZBLTSlG4n9M4EkYk12iZd02j/tG3xJtdlWd8ZZaCRULNae+h3dkO+4ZJi0cRxEte4THEJPOE8HEpRgyWViQydYo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708523089; c=relaxed/simple; bh=MNiTSCmiPanwd2UTFIrATfd6cKjvgt9t6dRwt7Xhp9k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=T50MuJFnXc3YHqUSIQEK2f8gvryM+8mnq64dGMoyeuVJNP9lcSDSzCxTNgY6Zd01X1nH+EmifZf7X3NxNUXlLSQ+0hV1KmGDXWGyxBlydHdRGjgxQ3LL02ArDACCXLxSCk3tr4AOdj2IWG2ZbakDCzaboxrtsLEJpZdNfTd2aWA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=SrSDHKe7; 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="SrSDHKe7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CAEACC433C7; Wed, 21 Feb 2024 13:44:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1708523089; bh=MNiTSCmiPanwd2UTFIrATfd6cKjvgt9t6dRwt7Xhp9k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SrSDHKe7kxgzRnuEiXPQtiNbYhq7pY2H5nc+k9XjJYf7L2WN3eJtYToaLLlbhSoNz jlGXHzLi2DHYJ1b49U+BX+gCSZJZu3LDWdolTsC3OKmVee3EwgDO36tjUg4/gu+mIZ ri6kT923/tECv+WQxy83RAi60jVh1koshyQgg+Wc= 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 5.15 336/476] hrtimer: Report offline hrtimer enqueue Date: Wed, 21 Feb 2024 14:06:27 +0100 Message-ID: <20240221130020.441289922@linuxfoundation.org> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240221130007.738356493@linuxfoundation.org> References: <20240221130007.738356493@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 5.15-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 @@ -197,6 +197,7 @@ enum hrtimer_base_type { * @max_hang_time: Maximum time spent in hrtimer_interrupt * @softirq_expiry_lock: Lock which is taken while softirq based hrtimer are * expired + * @online: CPU is online from an hrtimers point of view * @timer_waiters: A hrtimer_cancel() invocation waits for the timer * callback to finish. * @expires_next: absolute time of the next event, is required for remote @@ -219,7 +220,8 @@ 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 @@ -1082,6 +1082,7 @@ 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; @@ -2180,6 +2181,7 @@ 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; hrtimer_cpu_base_init_expiry_lock(cpu_base); return 0; } @@ -2247,6 +2249,7 @@ 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;