From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail3-165.sinamail.sina.com.cn (mail3-165.sinamail.sina.com.cn [202.108.3.165]) (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 71D63BA45 for ; Sun, 26 Jul 2026 02:10:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=202.108.3.165 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785031858; cv=none; b=GkmwbZtWEpMR4ukcYJ/bSHhT3iK1g7+Y7GiFIApOQlD0mRI9HfRp1+/dBs5t2RpEuDSCnX+xS1sEjZb4elXZfjlwF/2CcF42d1OAUeRC2tlL3NSFqvihgVlLkkh6FaRRwbK+G+Lce8NjSKo8oajzLj0S6ZLspd66qcf4axqa1Ns= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785031858; c=relaxed/simple; bh=5p5r2QfvmVJ2MA1kpwFuPmPk6PUZbCXrH4UURA4hnzw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cXSPKxo26tc1PDtLfiWod8jMMLeZCzo/9IoXnXY/UKkXyg9/AbVaQsT0UqK/E+fgs5kGpZ1BcKUyv3Lxz+CoS4rNmuYgziGC7uA4PBJZGzWlzzmbsLwj5tbrCoCgAnzizqCfEN2yFdMyQRiFO/hVvjx8Mn/D7seGF5huFKOLggw= 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=jZ+18M8X; arc=none smtp.client-ip=202.108.3.165 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="jZ+18M8X" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sina.com; s=201208; t=1785031853; bh=CCQnEbOJrULfCZYj1cl+RJhxmTf+c1w13H3ShWTdeAs=; h=From:Subject:Date:Message-ID; b=jZ+18M8Xi3csRn/xxI6zy5Xay289qgd5mRyYP0kxJEpR41aQGxK2VaEYebC6HuN8O Y0NfSV0p80ycO7vLVFoeFNKbSgdEUwcuD486HBwiI/4zQyCM5cfQDtXZCLQDTU1aGo 9KXjEH/fJ1rBVec690V6qhHmA7A/PJF/FmZDIohU= X-SMAIL-HELO: localhost.localdomain Received: from unknown (HELO localhost.localdomain)([221.216.154.155]) by sina.com (10.54.253.33) with ESMTP id 6A656C10000060CB; Sun, 26 Jul 2026 10:08:18 +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: 8844806685828 X-SMAIL-UIID: E43305900079454E9D1578A1349305B3-20260726-100818-1 From: Hillf Danton To: syzbot Cc: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [input?] possible deadlock in tasklet_action_common (2) Date: Sun, 26 Jul 2026 10:07:56 +0800 Message-ID: <20260726020807.722-1-hdanton@sina.com> In-Reply-To: <6a655704.70955b6c.323240.0028.GAE@google.com> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit > Date: Sat, 25 Jul 2026 17:38:28 -0700 [thread overview] > syzbot has found a reproducer for the following issue on: > > HEAD commit: cc2b5f627e8c Add linux-next specific files for 20260714 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=13d446b9580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=2290ccbf984c524f > dashboard link: https://syzkaller.appspot.com/bug?extid=b5d7ab56d43de3fd5aac > compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1310a232580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13c3b2ea580000 #syz test --- x/kernel/softirq.c +++ y/kernel/softirq.c @@ -924,7 +924,6 @@ static void tasklet_action_common(struct tl_head->tail = &tl_head->head; local_irq_enable(); - tasklet_lock_callback(); while (list) { struct tasklet_struct *t = list; @@ -944,7 +943,6 @@ static void tasklet_action_common(struct } } tasklet_unlock(t); - tasklet_callback_sync_wait_running(); continue; } tasklet_unlock(t); @@ -957,7 +955,6 @@ static void tasklet_action_common(struct __raise_softirq_irqoff(softirq_nr); local_irq_enable(); } - tasklet_unlock_callback(); } static __latent_entropy void tasklet_action(void) @@ -1006,11 +1003,10 @@ void tasklet_unlock_spin_wait(struct tas while (test_bit(TASKLET_STATE_RUN, &(t)->state)) { if (IS_ENABLED(CONFIG_PREEMPT_RT)) { /* - * Prevent a live lock when current preempted soft - * interrupt processing or prevents ksoftirqd from - * running. + * wait_on_bit(TASKLET_STATE_RUN) + * https://lore.kernel.org/lkml/20260524004526.1046-1-hdanton@sina.com/ */ - tasklet_callback_cancel_wait_running(); + tasklet_unlock_wait(t); } else { cpu_relax(); } --