From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) (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 4B37D275AF5; Mon, 5 Jan 2026 15:31:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.17 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767627096; cv=none; b=q3Znce0t2XjMWd6MkGaDzMeXS1qGyo9duQEppt89HBkfcNIeoHd/wDL4h7tkk42GXQhSYaZ1l6Hn1KPGJsfPHYrPGt9ShPxUxExmDeA3CsJM7qqm6DaIlpZNK2xOjokbSTlMbf+xKghTN338vrs/OEur84WtczYN8nuc2anyy88= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767627096; c=relaxed/simple; bh=fhbS21r0DEYIF4aR+XvrROnenWGn+ZEo2jFpNN4D15s=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=tRW6INyZqlKe6GOtXonMq3rHzOFkwBZWJVcDiq1HLzXAOrzqGR0Esgm/Tn+XR9tDdc4aPAPORWSl7WabYoFVLj86Pl4vQMOefZPy9k6P/2HwBwfXo+iLfz4aqCXivmliViAuH4DYCmgQOEtrv6FDGVKaEQ5Hzr0JE4fyyD6b0rM= 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=216.40.44.17 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 omf18.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id CE720B661A; Mon, 5 Jan 2026 15:31:25 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf18.hostedemail.com (Postfix) with ESMTPA id 1AFA630; Mon, 5 Jan 2026 15:31:23 +0000 (UTC) Date: Mon, 5 Jan 2026 10:31:45 -0500 From: Steven Rostedt To: Joel Fernandes Cc: linux-kernel@vger.kernel.org, "Paul E . McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Josh Triplett , Boqun Feng , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Uladzislau Rezki , joel@joelfernandes.org, rcu@vger.kernel.org Subject: Re: [PATCH RFC 01/14] rcu: Add WARN_ON_ONCE for blocked flag invariant in exit_rcu() Message-ID: <20260105103145.5b3eaaf5@gandalf.local.home> In-Reply-To: <20260103002343.6599-2-joelagnelf@nvidia.com> References: <20260103002343.6599-1-joelagnelf@nvidia.com> <20260103002343.6599-2-joelagnelf@nvidia.com> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-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: 1AFA630 X-Stat-Signature: 8c9djftkjbouqo131ctw7h5hgccj3qn5 X-Rspamd-Server: rspamout08 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX19Qy7KqdzUBPUoxr6Yu1sldc6piq+CDu0g= X-HE-Tag: 1767627083-56495 X-HE-Meta: U2FsdGVkX1/CMwVPDyPftzUIYBbvh4MYuTuRcK/jpkNkUUEavkCE/eoXfgpS6lybvaCGAlaD72wzQX4SXw83NT+o+BFMM/dJS8NKmoZ9DwF9ejOVGtq82VyzBuynDZyconYeJst4RFQ4Xt4uEACQfZ4M9AxFT/x6kZ2Gzaw2sPcJONdSFsckyZx/6uBdPGU2epza0nfum8JJv3DwflzujhESe9q1JpZn0/nAUTKdm8REpMXpQjYZPJUTWiWRtfp2UCUP3rquZGMkgBPu+VGCweozu/8GoguK9cj6bVFQgOMev6Dk71u3iWHtaL0SRMl1KCurJErOFpuEWQbeKkfqDtKPXBEQ09l2 On Fri, 2 Jan 2026 19:23:30 -0500 Joel Fernandes wrote: > Add a WARN_ON_ONCE to detect this invariant violation. If this > warning ever fires, it indicates a bug where a task was added to > a blocked list without properly setting the blocked flag first. > > Signed-off-by: Joel Fernandes > --- > kernel/rcu/tree_plugin.h | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > index dbe2d02be824..73ba5f4a968d 100644 > --- a/kernel/rcu/tree_plugin.h > +++ b/kernel/rcu/tree_plugin.h > @@ -846,6 +846,7 @@ void exit_rcu(void) > if (unlikely(!list_empty(¤t->rcu_node_entry))) { > rcu_preempt_depth_set(1); > barrier(); > + WARN_ON_ONCE(!t->rcu_read_unlock_special.b.blocked); > WRITE_ONCE(t->rcu_read_unlock_special.b.blocked, true); If we warn when it is not set, could we just remove setting it? Or do: if (WARN_ON_ONCE(!t->rcu_read_unlock_special.b.blocked)) WRITE_ONCE(t->rcu_read_unlock_special.b.blocked, true); -- Steve > } else if (unlikely(rcu_preempt_depth())) { > rcu_preempt_depth_set(1); > --