From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-173.mta0.migadu.com (out-173.mta0.migadu.com [91.218.175.173]) (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 1F25C23B601 for ; Thu, 31 Jul 2025 04:45:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753937133; cv=none; b=tXooZafY4ROZRtI/+VQgk3IBVp/l5gGXlCqlK6RihRrGLXhyzNvH7QGka4qTgiTET/74cQlUBKCpkBriz0lixvPhfJkgKlaFrHESld/S8HwNHeSmrUJYH9Fw+FvmtwYMfbhzK9qO/WXI/RipONT/MfiOOxbkhSSRRDudVshMqps= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753937133; c=relaxed/simple; bh=Xhm/zogzKFduolX5hF6WB1DtBaAhzXMfb09rTK3B8ts=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=gu5ME//F7Hc4LRuARiB1+/MWHEtipIqBBoQglLLEOSQE2e47c95DFGyrbNDVGrOCOjd1yZL6FSn+wnG1473jjDWgBejZa3xEGZxbkWxqPdCc8F/XpGl0HrR1ueI4Sa7pcyVZNJGvx6Pna929Ch7yeyYfZyx7mK097vlJ8YaET+E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=uQWSMEx4; arc=none smtp.client-ip=91.218.175.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="uQWSMEx4" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1753937127; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3GuYilt9iMvAMXVpxIhvpqryGMunfFXXWi/rj5lQQ9U=; b=uQWSMEx4T7bKu0KX+Qme5tr4Y2vMVosfSfCHPS/EdlHvNUY4Olr5j8odgPHieU/RDphF4y VdO+8AfeEyR7KnPIlhfp3OBHwcglBNWnXculEQM474bBs7OB027RxKV7fR3b2FZPDYcjFC jHDCTYnRl2fB2U4xTnm6jzT8gFcHcRI= Date: Thu, 31 Jul 2025 12:45:17 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v2] hung_task: Dump blocker task if it is not hung Content-Language: en-US To: Sergey Senozhatsky Cc: "Masami Hiramatsu (Google)" , Andrew Morton , Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , Waiman Long , Joel Granados , Anna Schumaker , Lance Yang , Kent Overstreet , Yongliang Gao , Steven Rostedt , Tomasz Figa , linux-kernel@vger.kernel.org References: <175391351423.688839.11917911323784986774.stgit@devnote2> <4c227812-23ef-4fe8-9bf1-cc4966fd31ac@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 2025/7/31 11:37, Sergey Senozhatsky wrote: > On (25/07/31 11:25), Lance Yang wrote: >>>> Wrote a simple 3 tasks circular lock test (same that I had in real >>>> life).  The output looks good: >>> >>> Nice work! The log is now much clearer ;) >> >> Forgot to add: >> >> This circular lock test is great. It would be very valuable to have >> it in samples/hung_task ;) >> >> Would you be willing to submit it as a patch? > > Well, that particular test is a deadlock, not sure how useful a test > that deadlocks is going to be. We probably need some alternative if > we want to test backtrace de-dup. Yep, you're right. A permanent deadlock is a no-go for a reusable test. Maybe we need a test like a blocker chain (T1->T2->T3), where T3 holds the lock and just sleeps for a while. Once it wakes up and releases the lock, everything can finish cleanly. Also, I might try to cook up a sample for that, time permitting ;)