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 737392D11AF; Mon, 14 Apr 2025 13:30:44 +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=1744637445; cv=none; b=Pxv/ch64i9qmQUNPd8YPljPwGZYyWn2ui5/b2FCvEC45faVswcLAsYCt4ZF9VSw5dwx4w/GR6TVa2sUUtAH3bOx+KyXj8c6w/RGZKRKpEr/rbGhwBhWxRyHh6U3jV4gDzNuczjZoQmCIydHeXWLXrjKSGeOWXdF6VjDNcUGuvS4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744637445; c=relaxed/simple; bh=yT53AX2C1X/ZgjzklomnAalqFEUWrqd7TesYE3PPwMQ=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=AquoCA2LZkyiO4tpHHl4JSWkwyy/FKhK2bNJIeNh+qBAqbLh1Bc1y9ptIJlSzmJkPfUfy++kxYEub2NCH9x0brO6LTa6X/WpfwdxknBig+ZJs5OlnyqhGKiu3RJaxaxupc0043Y0sscP27l4s0clNr/rCLjOq06ZB++MW+93YR4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Tc4ZCyDq; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Tc4ZCyDq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16FBDC4CEE2; Mon, 14 Apr 2025 13:30:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744637443; bh=yT53AX2C1X/ZgjzklomnAalqFEUWrqd7TesYE3PPwMQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Tc4ZCyDqEgcstzUSYXIF1GA5cTKmEPqPQHy1B/InMEJXub/jfYVd1wpshszlzuQZy i9LmOK9KMw3Nm9UnDOCZ1DiMPr+AsYYgzAc/VMdUVY4XT8SLRVB6TsWNM8e4ZaPuLy 2zfFER++rkqnBM+nLMDIPmgSXpnmowSMcVi//sVE6CreZuJU5SEqTRSHeoWdg4QMwC oPw/GQ25TvzjtTvWVapUx/PSMDPrNTRnhj3y98ENYNhsu2rJF2ayO9jraWLpjexciJ D2Zm6eTbPmi6f89uVmEJhk8w17msl9TMwAxM9CaQBcqW9KaoMjUBJ6dBgDTCxJIWN3 nAw7Ge/66t7xA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sebastian Andrzej Siewior , Borislav Petkov , Chris Bainbridge , Thomas Gleixner , Peter Zijlstra , Sasha Levin , anna-maria@linutronix.de, frederic@kernel.org, mingo@kernel.org, clrkwllms@kernel.org, rostedt@goodmis.org, linux-rt-devel@lists.linux.dev Subject: [PATCH AUTOSEL 6.6 22/24] timekeeping: Add a lockdep override in tick_freeze() Date: Mon, 14 Apr 2025 09:29:55 -0400 Message-Id: <20250414132957.680250-22-sashal@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250414132957.680250-1-sashal@kernel.org> References: <20250414132957.680250-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.6.87 Content-Transfer-Encoding: 8bit From: Sebastian Andrzej Siewior [ Upstream commit 92e250c624ea37fde64bfd624fd2556f0d846f18 ] tick_freeze() acquires a raw spinlock (tick_freeze_lock). Later in the callchain (timekeeping_suspend() -> mc146818_avoid_UIP()) the RTC driver acquires a spinlock which becomes a sleeping lock on PREEMPT_RT. Lockdep complains about this lock nesting. Add a lockdep override for this special case and a comment explaining why it is okay. Reported-by: Borislav Petkov Reported-by: Chris Bainbridge Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/all/20250404133429.pnAzf-eF@linutronix.de Closes: https://lore.kernel.org/all/20250330113202.GAZ-krsjAnurOlTcp-@fat_crate.local/ Closes: https://lore.kernel.org/all/CAP-bSRZ0CWyZZsMtx046YV8L28LhY0fson2g4EqcwRAVN1Jk+Q@mail.gmail.com/ Signed-off-by: Sasha Levin --- kernel/time/tick-common.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c index 7f2b17fc8ce40..ecdb8c2b2cab2 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -495,6 +495,7 @@ void tick_resume(void) #ifdef CONFIG_SUSPEND static DEFINE_RAW_SPINLOCK(tick_freeze_lock); +static DEFINE_WAIT_OVERRIDE_MAP(tick_freeze_map, LD_WAIT_SLEEP); static unsigned int tick_freeze_depth; /** @@ -514,9 +515,22 @@ void tick_freeze(void) if (tick_freeze_depth == num_online_cpus()) { trace_suspend_resume(TPS("timekeeping_freeze"), smp_processor_id(), true); + /* + * All other CPUs have their interrupts disabled and are + * suspended to idle. Other tasks have been frozen so there + * is no scheduling happening. This means that there is no + * concurrency in the system at this point. Therefore it is + * okay to acquire a sleeping lock on PREEMPT_RT, such as a + * spinlock, because the lock cannot be held by other CPUs + * or threads and acquiring it cannot block. + * + * Inform lockdep about the situation. + */ + lock_map_acquire_try(&tick_freeze_map); system_state = SYSTEM_SUSPEND; sched_clock_suspend(); timekeeping_suspend(); + lock_map_release(&tick_freeze_map); } else { tick_suspend_local(); } @@ -538,8 +552,16 @@ void tick_unfreeze(void) raw_spin_lock(&tick_freeze_lock); if (tick_freeze_depth == num_online_cpus()) { + /* + * Similar to tick_freeze(). On resumption the first CPU may + * acquire uncontended sleeping locks while other CPUs block on + * tick_freeze_lock. + */ + lock_map_acquire_try(&tick_freeze_map); timekeeping_resume(); sched_clock_resume(); + lock_map_release(&tick_freeze_map); + system_state = SYSTEM_RUNNING; trace_suspend_resume(TPS("timekeeping_freeze"), smp_processor_id(), false); -- 2.39.5