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 570551A23A9 for ; Thu, 4 Sep 2025 06:12:49 +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=1756966371; cv=none; b=XjUvnNdOkDw3NTBNMaqxUciCbFSLYKFnKsmQ9U7t4jDeL+uBxCeqM8FXUbkBFjm/zn7COZ5K5/EmecR796DZKGWBZ7/pp06lZe4G1PwmVrmnSuAY5PUNmmOuJeV3LgDkFoa1ErIJCevOgmlmtf/MoFGL6dTQm89I7SeqoXAgrHc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756966371; c=relaxed/simple; bh=T2M5y5iMBdFOk0EziNCklAQ5vJkE7v8Re9oP1RjijIo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OL0ouPpCw84eh/xe4ThljjYtI887Hxu6vy9pZfDipQYfYwI23GBZ52Jl7vnlowkdEfmFHm3HH2J2i0/pFzSrtNHG0vfWBSKX0OQAvMquWhz6ouqnVGhF9skx0fpYq1h+9YtYz1SbVNQsrer6XbIDPEREHqp6tkfy8KM5/68M3H0= 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=L3mF1Nr5; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=hTa4MJJO; 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="L3mF1Nr5"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="hTa4MJJO" Date: Thu, 4 Sep 2025 08:12:45 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1756966367; 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=WeOH+JVqba84dXKrauDtj8cgh1+G+Z0Etd6YWsUVtLI=; b=L3mF1Nr5efzsm2ttbOUUDu0Ptqnk9D6e2Hqj26ORwJnRos2Yj7dzvxgSbQ/+NrWeckd4Gl RNZ9buNAb/Nl/8yy5BOE/Mfw3sGjGAtrsZJ8g/yhdr1si5jU3RqCumzbwBACk/i2xR7Zhi FjoSCAV8qCQP3mfsSGte0sOA2j9a5oNNHKLbWnhEQWizC+0ArVh2aK3GPds76pVxR43X4b 6bQpud1nzq4zLV0nZ94DvdBJL2e759Dn/ZubJJxndWSaGta9i/Nkoi+heZxYgBIkqNBGew x7ceOjPSVLzrmgDmPofLbCNIt2QbddJMAVac+uWCASD34ohV26moJQMMGFbIjw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1756966367; 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=WeOH+JVqba84dXKrauDtj8cgh1+G+Z0Etd6YWsUVtLI=; b=hTa4MJJOP945AHUb8R7x3iU5Wh8FMAG2OQ0ha2ZnOAEkXEruMGRy/oPpeA+sEvT7zCi8o9 2Y12+yNGJZiACTDQ== From: Sebastian Andrzej Siewior To: Hillf Danton Cc: syzbot , linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [sound?] possible deadlock in __snd_pcm_lib_xfer (2) Message-ID: <20250904061245.pqGf3VwT@linutronix.de> References: <68b269e9.a00a0220.1337b0.001f.GAE@google.com> <20250830065638.6116-1-hdanton@sina.com> <20250904010529.6410-1-hdanton@sina.com> 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: <20250904010529.6410-1-hdanton@sina.com> On 2025-09-04 09:05:28 [+0800], Hillf Danton wrote: > On Wed, 3 Sep 2025 16:59:05 +0200 Sebastian Andrzej Siewior wrote: > > On 2025-08-30 14:56:37 [+0800], Hillf Danton wrote: > > > > syz.0.46/6843 is trying to acquire lock: > > > > ffff8880b8823d90 ((softirq_ctrl.lock)){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline] > > > > ffff8880b8823d90 ((softirq_ctrl.lock)){+.+.}-{3:3}, at: __local_bh_disable_ip+0x264/0x400 kernel/softirq.c:168 > > > > > > > Given softirq_ctrl is percpu, this report is false positive. > > > > No. This can happen on a single CPU. > > > But the single CPU theory fails to explain the deadlock reported. > > > > > Possible unsafe locking scenario: > > > > > > > > CPU0 CPU1 > > > > ---- ---- Thead0 Thread1 ------ -------c > > > > lock(&group->lock#2); preempt to -> > > > > lock((softirq_ctrl.lock)); > > > > lock(&group->lock#2); <- preempt to > > > > lock((softirq_ctrl.lock)); > > > > > > > > *** DEADLOCK *** now nobody makes progress Sebastian