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 BBA1A258EFB for ; Wed, 1 Oct 2025 15:30:16 +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=1759332620; cv=none; b=mA5yRQdUizLzIWDtama2g7b+YSC3F64bSL8+010WxLvdErq+O9bGuuupSssMlrw8Tzp5u2VzfgEBd4Ldd8X3zKIZBUgq8Tg0cm2b+BAf94LRtWMAuINzB202Vu2yTwi7R8p7oQE3FDN6xFbGbt59+FHgJ9ByJNQRLHhy5kOKIEQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759332620; c=relaxed/simple; bh=CXwG/R+Rnn7AkKam2k9JX1aU4zJyU59IGQaNQgzAeno=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=BYDobvufUicWVmUEWYCpCl+CbT8pZ4yoG1tgHlWLfexQ7tEQXuJhTGFRAtWzRfa7tDHE2HkervQg/QC8YD68awTW7sptSxaDnfWQtAW4BCAZVRh8gDIIAFJarMjpbXZVlNT3riFmylXre2Ci2bvLqau9N4L8nzdl7IqIadZM39g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (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=none (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 9AC0E55EB1; Wed, 1 Oct 2025 15:30:09 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf10.hostedemail.com (Postfix) with ESMTPA id CECBA2F; Wed, 1 Oct 2025 15:30:07 +0000 (UTC) Date: Wed, 1 Oct 2025 11:31:45 -0400 From: Steven Rostedt To: Peter Zijlstra Cc: jpoimboe@kernel.org, rostedt@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 01/12] task_work: Fix NMI race condition Message-ID: <20251001113145.72e10530@gandalf.local.home> In-Reply-To: <20250924080118.425949403@infradead.org> References: <20250924075948.579302904@infradead.org> <20250924080118.425949403@infradead.org> 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-Stat-Signature: wm1u53iazytns5ejtjdsh13a91rrk6bk X-Rspamd-Server: rspamout01 X-Rspamd-Queue-Id: CECBA2F X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1+NQk0AiKdfmpm0DXOLHjBnoUgAsU6cNCw= X-HE-Tag: 1759332607-190467 X-HE-Meta: U2FsdGVkX1/lqmIJhBB/K2L6Gh7XKgysIB7soH30sjN++xRp9QFU3SXockUFgkpFdSHQjf46BNjBnd0r8pBpg5ZnaeFJh4aDfPWFwTQj3qYY0qcpHmdb2oRUB/87A4cjRZiAqjGI0hKvP6YmXXmSg6PTwfYotZ0h0JdYb6zeqpy9o2hTwMHfLd2jmTyYE5yO/i1a6XYIQFO/Fdv7ff8w8jKQ7BO3zT99Np/GaIX9lQaPME9ZUSLrCJJWkfhwVIkZ35KhM2XoFv4DIZTHJevm/hRq/TfO7+7RONmgp1VvUCt4QJpF/yT82oskjDom3RAjE/TMb9gqP9IGpOdMamqhU6xLq8rM1ieR2yyMKT7hfytNzJSne2uYu8+79DZbJJ4nJGh4j8H82tdVuuuzbgWLeLwuYRU0wMN1e6ol4QX6UMvimJlMmq9/Rt6GQKKx/jh2/X0HnEi+pQ2mMLcbrFe7Lg== On Wed, 24 Sep 2025 09:59:49 +0200 Peter Zijlstra wrote: > __schedule() > // disable irqs > > task_work_add(current, work, TWA_NMI_CURRENT); > > // current = next; > // enable irqs > > task_work_set_notify_irq() > test_and_set_tsk_thread_flag(current, > TIF_NOTIFY_RESUME); // wrong task! > > // original task skips task work on its next return to user (or exit!) > > Fixes: 466e4d801cd4 ("task_work: Add TWA_NMI_CURRENT as an additional notify mode.") > Reported-by: Josh Poimboeuf > Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Steven Rostedt (Google) -- Steve