From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail3-167.sinamail.sina.com.cn (mail3-167.sinamail.sina.com.cn [202.108.3.167]) (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 4E05F29D0E for ; Thu, 4 Sep 2025 01:06:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=202.108.3.167 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756947987; cv=none; b=V1jbyg0y7C8rraIJxm5/8Xf8EEePbV790UbKWEnQGb9/f0Z+Gj6cORNawjXL3EGHkHr0dgrXS2N2J4cwXwV14YkKhsYx15XI+GUpXse58KxAFhEIcRNMNqcRGiDJMFqqvpKgQTmse1WcP+KfH/lZHLN6tZWJb8a+vjmuYasumgg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756947987; c=relaxed/simple; bh=Y5FkXg1q+l+bANYuU78sTSjCfRhtQEMrq4gwoYi2ZcY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BP4PqZvH0qxLtJhKjzJrjU8tFA96KEdsr2lWNcR9+bUnr+l5quxHOTHlFP4VdgkasGdUWecke52lJSUfEO4mUPj30fIywwJkMrBfdKfLwt8aYCm5d7ksU+g5b1XijO/CAjzNPGoA4FMyN5RVDl9u2IPtQqTiODIPShD5YoI6XEU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sina.com; spf=pass smtp.mailfrom=sina.com; dkim=pass (1024-bit key) header.d=sina.com header.i=@sina.com header.b=yMOZg30Y; arc=none smtp.client-ip=202.108.3.167 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sina.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sina.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=sina.com header.i=@sina.com header.b="yMOZg30Y" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sina.com; s=201208; t=1756947982; bh=1PRX40VDXKt5fdkyOugUQheA0/3kNkmIu8jTLpAcbrQ=; h=From:Subject:Date:Message-ID; b=yMOZg30Y3zWFiW7jenptpOQ7zFYYw4dS0DWBUV5mKSCf62Dg52FYkvKxit9DrMrh2 uxst5HfxM5mJDYSZJQgMITcfHME49cFspLDEhyI17VslRV9IAAm4JI7BJv1w4uDUfx yHl/4EZ0hDsWqZqI5t7AZV1e/PdqApBpnYA14ObA= X-SMAIL-HELO: localhost.localdomain Received: from unknown (HELO localhost.localdomain)([114.249.58.236]) by sina.com (10.54.253.33) with ESMTP id 68B8E5E000002BF5; Thu, 4 Sep 2025 09:05:38 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com Authentication-Results: sina.com; spf=none smtp.mailfrom=hdanton@sina.com; dkim=none header.i=none; dmarc=none action=none header.from=hdanton@sina.com X-SMAIL-MID: 2775386685278 X-SMAIL-UIID: 7201085AE2EC48469630045E6EB342DF-20250904-090538-1 From: Hillf Danton To: Sebastian Andrzej Siewior Cc: syzbot , linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [sound?] possible deadlock in __snd_pcm_lib_xfer (2) Date: Thu, 4 Sep 2025 09:05:28 +0800 Message-ID: <20250904010529.6410-1-hdanton@sina.com> In-Reply-To: <20250903145905.r7Ak4Wya@linutronix.de> References: <68b269e9.a00a0220.1337b0.001f.GAE@google.com> <20250830065638.6116-1-hdanton@sina.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 > > > ---- ---- > > > lock(&group->lock#2); > > > lock((softirq_ctrl.lock)); > > > lock(&group->lock#2); > > > lock((softirq_ctrl.lock)); > > > > > > *** DEADLOCK ***