From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) (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 ABADF38657A for ; Fri, 17 Apr 2026 12:43:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.13 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776429804; cv=none; b=JYW7NBc+pEJFovG8SNTbsIaIwYUCp0+Q7Yqh/tUxNoTqnpmPypScSGShdjuxQOhhIFiMuyj7bV0p9IvfwvrLNpKG/Y1vNekoMlmf7ffhlEfER/mDKtEvRTDeyZG4zd6qccFO/ZnwcTusNAYyUuF+XVEQdcjOzN1uUYZCOIknUF0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776429804; c=relaxed/simple; bh=+PAbqegMY7ms1pD/DDXxPS8/rMytrT9AEI3vd3+narA=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=PeN3VI4rwkcyhorTgqFpP3eVK/YHuA/jAS4KHoSAZ49ewuSAbOfHysd0Qha05qgkWzxwZzpJ2SXLGfq7m/7afNeBJCs4p6Xpe9XxRLuUcEghzUnl7YSAl0QeZotlPAkEhHePgPnWjqkkFlVh4237RmjVEAyXz4U5cs0sOKPIeYc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.13 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id BFB6D1A0181; Fri, 17 Apr 2026 12:43:20 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf05.hostedemail.com (Postfix) with ESMTPA id 0649E20011; Fri, 17 Apr 2026 12:43:17 +0000 (UTC) Date: Fri, 17 Apr 2026 08:43:13 -0400 From: Steven Rostedt To: "Paul E. McKenney" Cc: LKML , Frederic Weisbecker , Joel Fernandes , Eric Dumazet , Kuniyuki Iwashima , Paolo Abeni , Willem de Bruijn , Yao Kai Subject: Re: [WARNING] RCU stall in sock_def_readable() Message-ID: <20260417084313.010864e8@fedora> In-Reply-To: References: <20260415132722.788bbdcf@fedora> X-Mailer: Claws Mail 4.3.1 (GTK 3.24.52; x86_64-redhat-linux-gnu) 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=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 0649E20011 X-Rspamd-Server: rspamout06 X-Stat-Signature: iuj1gczat1pk7d9m6ibbcidnnfpbozy1 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX19tMaSqYsDaFpTytZB4YF9i07H4jda4NwU= X-HE-Tag: 1776429797-222813 X-HE-Meta: U2FsdGVkX19Be3ooquoKtnDYgjorRpoE13sz3Icug5BaOP/7PDlXLXMVlIHHiIKAd7IytdP+ux78xrTwDkSPeHYWs5/mLtUBWYUgSN63PtPLXDYy1PRlQ+uqxPFqa2he2IViylbJnnIAHr/PY9GbOqHk7hy/pyMbwD7QAg5i4iMyKQNY2LytfsEObOJzO1h4SnIgMwXnhz5KaNe9KB2DxEnEjMzL+HHbCtHsHFQTuKTdlIP8m2960m9LcDPKvFEn9VUoa+sqgs4TeoMGLJMBsAYDe5lRKlOKktiQAxBkEdPjwXqQQSapi+Xi/h4YyNIROkEnLvHuUkKELaRp4syrVEWCSoxV6/DD On Thu, 16 Apr 2026 17:16:11 -0700 "Paul E. McKenney" wrote: > One "hail Mary" thought is to revert this guy and see if it helps: > > d41e37f26b31 ("rcu: Fix rcu_read_unlock() deadloop due to softirq") > > This commit fixes a bug, so we cannot revert it in mainline, but there > is some reason to believe that there are more bugs beyond the one that > it fixed, and it might have (through no fault of its own) made those > other bugs more probable. > > Worth a try, anyway! Hail mary's are worth a try, but the reason they call it a hail mary is because it is unlikely to succeed :-p run test ssh -t root@tracetest "trace-cmd record -p function -e syscalls /work/c/hackbench_64 50" ssh -t root@tracetest "trace-cmd record -p function -e syscalls /work/c/hackbench_64 50" ... [ 209.590500] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: [ 209.592620] rcu: Tasks blocked on level-0 rcu_node (CPUs 0-3): P3151/1:b..l [ 209.595266] rcu: (detected by 0, t=6502 jiffies, g=29673, q=186 ncpus=4) [ 209.597557] task:hackbench_64 state:R running task stack:0 pid:3151 tgid:3151 ppid:3144 task_flags:0x400000 flags:0x00080000 [ 209.601871] Call Trace: [ 209.602852] [ 209.603752] __schedule+0x4ac/0x12f0 [ 209.605172] preempt_schedule_common+0x26/0xe0 [ 209.606755] ? preempt_schedule_thunk+0x16/0x30 [ 209.608337] preempt_schedule_thunk+0x16/0x30 [ 209.609973] ? _raw_spin_unlock_irqrestore+0x39/0x70 [ 209.611688] _raw_spin_unlock_irqrestore+0x5d/0x70 [ 209.613408] sock_def_readable+0x9c/0x2b0 [ 209.614841] unix_stream_sendmsg+0x2d7/0x710 [ 209.616420] sock_write_iter+0x185/0x190 [ 209.617934] vfs_write+0x457/0x5b0 [ 209.619242] ksys_write+0xc8/0xf0 [ 209.620532] do_syscall_64+0x117/0x1660 [ 209.621936] ? irqentry_exit+0xd9/0x690 [ 209.623319] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 209.625199] RIP: 0033:0x7f603e8e5190 [ 209.626628] RSP: 002b:00007ffd003f99c8 EFLAGS: 00000202 ORIG_RAX: 0000000000000001 [ 209.629304] RAX: ffffffffffffffda RBX: 00007ffd003f9b58 RCX: 00007f603e8e5190 [ 209.631710] RDX: 0000000000000001 RSI: 00007ffd003f99ef RDI: 0000000000000006 [ 209.634200] RBP: 00007ffd003f9a40 R08: 0011861580000000 R09: 0000000000000000 [ 209.636638] R10: 00007f603e8064d0 R11: 0000000000000202 R12: 0000000000000000 [ 209.639050] R13: 00007ffd003f9b70 R14: 00005637df126dd8 R15: 00007f603ea10020 [ 209.641600] Detected kernel crash! That was with the revert :-( -- Steve