From mboxrd@z Thu Jan 1 00:00:00 1970 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 DCA4B171E5C; Fri, 5 Apr 2024 17:52:18 +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=1712339540; cv=none; b=mLg8cz5xvMx6jYqRl3Bn5Ij6azqpcJm6YskxkUyAF2CL7ctmWJgV5NP2rEIW/LVFs31Sq5a76u4y0/W7tXP4aQPWb0aiodnw79JRPsTygw7IU6VKXX2M/AI1tk4hg5pMLWsyQIEOTbe/OVMR4URkjIm8SyYFipKCDJXi0ObqBDc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712339540; c=relaxed/simple; bh=j7yhX/0k89FjgZpWop60wH7jFudilKgIEAQOT4pmwFc=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=f8iKmwizXXOS/tCqms7UKU0Zs4KC5yxezLD7qSmHSk/z/6kVhMAbcYKzF/aWRHVJIaCEqyMfJhJTbhLn3laMOu0QsRhtbqyAURP5n21kRS7+1OKqNlMnrLAP+7P8Aq8uwkZutCKRBsxZmPWWpBkh0oU211DcRt1mJMdLdBsRh7M= 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=pp8ex2Zs; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=21i9kyjH; 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="pp8ex2Zs"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="21i9kyjH" From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1712339536; 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: in-reply-to:in-reply-to:references:references; bh=j7yhX/0k89FjgZpWop60wH7jFudilKgIEAQOT4pmwFc=; b=pp8ex2ZsLRPjTgD5B64xpI/Ztqb+a3c8XLyOM5lBZ0X1XlPNn3N443JQJUPx2FFIult+gD CnvtHY7LJ9vfRpbMZdNITpA25tjaumpkzjcwinlKxPVsdEhdmNF5B4DGXEiy16ua3msDPZ 7hTg5OmQ8FdNj2892/9G0aZhEZrGLjTSN9AweM2WrRt/4Qu8yPvCs+NIHEeQHXGo1SGwt6 5Fy+boPBiIHxgq64uU0ZfsD52t5ci2Y/zFzPLdahPkbqcvVbUevdVc+cqoFocjpEFlFpDc aghVnAc3Tx4AR63TJ1VTchMZcbzd8NBcu6P7bWdgDc/OPyIRgO7yh0kfSeXvBA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1712339536; 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: in-reply-to:in-reply-to:references:references; bh=j7yhX/0k89FjgZpWop60wH7jFudilKgIEAQOT4pmwFc=; b=21i9kyjHmB1jIK0h8UR8AjeiTCXFhrCFrthxjn9uL94YkY2aosXsbD20lo2w9pvGyV1cHr LoK9FbGzohFzFhCw== To: Anna-Maria Behnsen , linux-kernel@vger.kernel.org Cc: "Rafael J . Wysocki" , Pavel Machek , Len Brown , Ulf Hansson , linux-pm@vger.kernel.org, Frederic Weisbecker , x86@kernel.org, Anna-Maria Behnsen , Mario Limonciello , stable@kernel.org Subject: Re: [PATCH] PM: s2idle: Make sure CPUs will wakeup directly on resume In-Reply-To: <20240405083410.4896-1-anna-maria@linutronix.de> References: <20240405083410.4896-1-anna-maria@linutronix.de> Date: Fri, 05 Apr 2024 19:52:16 +0200 Message-ID: <87jzlb8zov.ffs@tglx> Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Fri, Apr 05 2024 at 10:34, Anna-Maria Behnsen wrote: > s2idle works like a regular suspend with freezing processes and freezing > devices. All CPUs except the control CPU go into idle. Once this is > completed the control CPU kicks all other CPUs out of idle, so that they > reenter the idle loop and then enter s2idle state. The control CPU then > issues an swait() on the suspend state and therefore enters the idle loop > as well. > > Due to being kicked out of idle, the other CPUs leave their NOHZ states, > which means the tick is active and the corresponding hrtimer is programmed > to the next jiffie. > > On entering s2idle the CPUs shut down their local clockevent device to > prevent wakeups. The last CPU which enters s2idle shuts down its local > clockevent and freezes timekeeping. > > On resume, one of the CPUs receives the wakeup interrupt, unfreezes > timekeeping and its local clockevent and starts the resume process. At that > point all other CPUs are still in s2idle with their clockevents switched > off. They only resume when they are kicked by another CPU or after resuming > devices and then receiving a device interrupt. > > That means there is no guarantee that all CPUs will wakeup directly on > resume. As the consequence there is no guarantee that timers which are s/As the/As a/ > queued on those CPUs and should expire directly after resume, are > handled. Also timer list timers which are remotely queued to one of those > CPUs after resume will not result in a reporgramming IPI as the tick is s/reporgramming/reprogamming/ > active. A queue hrtimer will also not result in a reprogramming IPI because s/A queue/Queueing a/ > the first hrtimer event is already in the past. > > The recent introduction of the timer pull model (7ee988770326 ("timers: > Implement the hierarchical pull model")) amplifies this problem, if the > current migrator is one of the non woken up CPUs. When a non pinned timer > list timer is queued and the queueing CPU goes idle, it relies on the still > suspended migrator CPU to expire the timer which will happen by chance. > > The problem existis since commit 8d89835b0467 ("PM: suspend: Do not pause > cpuidle in the suspend-to-idle path"). There the cpuidle_pause() call which > in turn invoked a wakeup for all idle CPUs was moved to a later point in > the resume process. This might not be reached or reached very late because > it waits on a timer of a still suspended CPU. > > Address this by kicking all CPUs out of idle after the control CPU returns > from swait() so that they resume their timers and restore consistent system > state. > > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218641 > Fixes: 8d89835b0467 ("PM: suspend: Do not pause cpuidle in the suspend-to-idle path") > Signed-off-by: Anna-Maria Behnsen > Tested-by: Mario Limonciello > Cc: stable@kernel.org Reviewed-by: Thomas Gleixner