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 E992D3A1689; Tue, 8 Sep 2026 07:54:59 +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=1788854101; cv=none; b=uO+Lh9GitDuElpPlhad+OS0XYAqXbnVcHTtAplYkW+Jx61IW/KVxfVrDTK61SMpiB3Swnl63OFrHIokPYsRTH/TryYKaajwuEb3QTPdrEUTTXcKb+guBsP1KUEyITP0ms/QCsrEZUkIPxo6Sg3cAU/jkrUP4xD0MNaRgXhQDrv4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788854101; c=relaxed/simple; bh=V74iGfBs4xj3cXo0HtXboe4bqdfUosm7GEnus1leJfE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Oz7gzGcrvow85ljNKZTorIpopS4QHdqBwp2uy2n+WM37OSlyksrFcTcgjM93RQa6UUBN6+5/G2YohHp2Cd/AGY+osq/zgO9gncCy7Q367er0ZK0Lm97F0FFDpYak/e2R0zka9jnfTxeB1lD1p047zSIhIkYRaDawK3XLuaXEouQ= 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=MTDe8PJK; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=Ywr7ePjS; 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="MTDe8PJK"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Ywr7ePjS" Date: Tue, 8 Sep 2026 09:54:55 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1788854097; 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=VRXRVay6xLDZY+t9lcPrWvUb1XaHgPwRKdlm/Zpxbzo=; b=MTDe8PJKy74mVVCxKtrjvDjyETtY0k1cqzIZziqdC7jbt6wfLpZ8zhjCzYpJhCHwy6wuYK 6hrzjO7dmx3Al/CY1uADqQXo7Tu2Ofg067RiGi9q/GcFvIKwr5Xd3bi7+kJQlem0obsdiU TaV/TbrSrslnYKCYD30aBmCsK9zFgBjkog6SvsQNGEFYh63ifrd4eXgA79Dosp7qiUtkr7 B5dgUPYhGyJwVGhgOq5lZ1lBg3PA5fbC9JcqYLwTW9ivMi/9zJkVIvCPQEtWJhCEvjsf1C iDjhnl7Bg85zPff4JVLn4D2s9LJazauY0Qw/zlTNNegPjA+s0deMXaDvLCFVjg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1788854097; 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=VRXRVay6xLDZY+t9lcPrWvUb1XaHgPwRKdlm/Zpxbzo=; b=Ywr7ePjS5TdqcKhAM5Xa5HO7Cqd6lr5qXZOzO2PgPrTykoYnGCTddGdthPyYuioQvx9hLm xyfCWP7dsxUfByCg== From: Sebastian Andrzej Siewior To: Russell King Cc: Steven Rostedt , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, linux-perf-users@vger.kernel.org, loongarch@lists.linux.dev, Mark Rutland , Ian Rogers , Peter Zijlstra , "Luis Claudio R. Goncalves" , Catalin Marinas , James Clark , Huacai Chen , Adrian Hunter , Oleg Nesterov , Alexander Shishkin , Ingo Molnar , Arnaldo Carvalho de Melo , Jiri Olsa , Namhyung Kim , Waiman Long , WANG Xuerui , Will Deacon , Clark Williams Subject: Re: [PATCH v2] ARM, ARM64, LONGARCH: Delay HW BP notification to task_work() Message-ID: <20260908075455.OffmMhrB@linutronix.de> References: <20260814085118.OPEA_Ssn@linutronix.de> <20260903160710.vVf4gEL2@linutronix.de> <20260903133146.07095885@gandalf.local.home> <20260904155404.ESPFg3zi@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On 2026-09-07 15:46:09 [+0100], Russell King wrote: > On Fri, Sep 04, 2026 at 05:54:04PM +0200, Sebastian Andrzej Siewior wrote: > > On 2026-09-03 13:31:46 [-0400], Steven Rostedt wrote: > > > On Thu, 3 Sep 2026 17:47:24 +0100 > > > Russell King wrote: > > > > > > > What do you expect to happen with this? Which arch maintainer should > > > > apply this patch that affects three different independently maintained > > > > architectures? > > > > Well, if you as the ARM person are fine with ARM part, an ACK would be > > appreciated. If you have something to object, it would be nice to let me > > know so I can adjust accordingly. > > First, I only just looked at the email - you may have noticed I'm not > very active with the kernel anymore, as I'm a full-time carer at the > moment. > > Second, I'm not fine with the patch as-is, because it's not clear how > it could be merged in its current form. It would be inappropriate to > give an Ack, because an Ack means I'm fine with it. I'm not. > > Third, I haven't actually reviewed the patch itself (see first point). > > Looking deeper now, I see nothing in the linked report, nor in your > write-up that identifies what is responsible for the context being > inappropriate to deliver the SIGTRAP. See the first point - I'm not The linked report shows a backtrace by "BUG: sleeping function" originating from el0_breakpt() -> perf_bp_event() following by sending a signal force_sig_fault() followed by rt_spin_lock() and __might_resched(). It also contains a reproducer. The first sentence has the part | The hardware event is | delivered with disabled interrupts and perf intrastrucure expects | disabled interrupts while the overflow callback is invoked. This is what happens, followed by | The callback then sends a SIGTRAP signal for which it acquires | sighand_struct::siglock, a spinlock_t which becomes a sleeping lock and | must not be acquired in atomic context. This is not really specific to PREEMPT_RT as we enforce to not allow raw_spinlock_t -> spinlock_t on !PREEMPT_RT via lockdep, too. > able to read lots of code to work that out, and presumably you've > already done that ground work to come up with a fix. This is *vital* > information when someone looks back at why this change was made as > it helps to understand how the problem occurs. This is, after all, > the whole point of commit messages - to help people look back and > understand why a change was made. The "what the changes are" part > is already covered by the patch showing what the changes were. It's > the stuff that *isn't* in the patch that needs to be in the commit > message. > > So... don't describe the code changes in a commit message. I think both parts (describing the issue and the change) are part of the commit message. > So no, an Ack is not appropriate. Sebastian