From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from r3-25.sinamail.sina.com.cn (r3-25.sinamail.sina.com.cn [202.108.3.25]) (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 EC6FD3C38 for ; Tue, 29 Jul 2025 01:07:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=202.108.3.25 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753751276; cv=none; b=hP3ojkfK+N0Rufx/Nf2H0MzX/kqZxHWWlYUkotG5O6Ri/Z2CC2tmqtyOHxSNPsTpROEn8UeXokfPggslT8kr8kOof/hRknAga8mrqSQpPaFMVavv/zmDQvW9xo74BTGM8akR7miWPyP9wDkxI92eGK7egeR93E4sjOzWKbuEhsQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753751276; c=relaxed/simple; bh=WD9FaDGb63M7KxP1pupSuXLBiDk6KJua+yjTVfbjOzg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZPGYcQrVDJu2uSy20ISTrwX/3AJ6bxYKaY/XRHfXl7Gzlaz8uVvuAIynUW/vF5FCRxnIYSONXQcWrpw899WB47+bmUAy/bFUUjLQnDs60CWLeAvS7x9tXxHZtPcvIxmfl39kc4QenZjBO19dTyA3wqpaV7MorJWKPJa8WrWzMGA= 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=lFYVquxP; arc=none smtp.client-ip=202.108.3.25 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="lFYVquxP" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sina.com; s=201208; t=1753751271; bh=DJcvxvLUlEjzlD05x0/DLHsYRHP+TmolVpjDi1qmHVs=; h=From:Subject:Date:Message-ID; b=lFYVquxPKGTlfEISnlmLH+d2ssEIdIdk0q47lFj4u+KfeWeF8GT7PdG75mkgBokjM w/pcQ2NaPPTZD2hsbUG0YkP9chFBgTdC/5FrVvp2A5lnlLqMDHXZTYp5IC49zdDHO9 7lYVYkZN4+k+rLYdM3Q7Yp4ZiB0PU3laM8jzoKco= X-SMAIL-HELO: localhost.localdomain Received: from unknown (HELO localhost.localdomain)([114.249.58.236]) by sina.com (10.54.253.31) with ESMTP id 68881EB900004E84; Tue, 29 Jul 2025 09:07:07 +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: 5217856816227 X-SMAIL-UIID: DBB33BB01FC348DCB0C814F4A4CB1DB1-20250729-090707-1 From: Hillf Danton To: syzbot Cc: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [mm?] INFO: rcu detected stall in exit_to_user_mode_loop Date: Tue, 29 Jul 2025 09:06:56 +0800 Message-ID: <20250729010657.3326-1-hdanton@sina.com> In-Reply-To: <6887ebf4.a00a0220.b12ec.00ae.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: Mon, 28 Jul 2025 14:30:28 -0700 [thread overview] > syzbot has found a reproducer for the following issue on: > > HEAD commit: afd8c2c9e2e2 Merge branch 'ipv6-f6i-fib6_siblings-and-rt-f.. > git tree: net > console output: https://syzkaller.appspot.com/x/log.txt?x=13c71034580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=a4bcc0a11b3192be > dashboard link: https://syzkaller.appspot.com/bug?extid=2642f347f7309b4880dc > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17b284a2580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17c71034580000 #syz test upstream master --- x/net/sched/sch_taprio.c +++ y/net/sched/sch_taprio.c @@ -918,7 +918,7 @@ static enum hrtimer_restart advance_sche int num_tc = netdev_get_num_tc(dev); struct sched_entry *entry, *next; struct Qdisc *sch = q->root; - ktime_t end_time; + ktime_t end_time, now; int tc; spin_lock(&q->current_entry_lock); @@ -980,6 +980,11 @@ first_run: rcu_assign_pointer(q->current_entry, next); spin_unlock(&q->current_entry_lock); + now = timer->base->get_time(); + now = ktime_add_us(now, 2); + /* is end_time sane? */ + if (ktime_after(now, end_time)) + end_time = now; hrtimer_set_expires(&q->advance_timer, end_time); rcu_read_lock(); --