From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4921623182D; Mon, 29 Dec 2025 17:39:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767029957; cv=none; b=F7AE9YRiQyEEeyyc0/hhaRL5sC5sNFKiW1fb/dcQik5QbM6qTxhTj6tFL++hP4YSjjLo82EKDT+rT4IMZ4BYYCpGE8nVQ4MwCH20bIdQPbsfutjUNeDEiGn/RWZEora5VxWvC6/GomTkgMTzOtzfEITX/zVtkP4aYpD3xq0NjuU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767029957; c=relaxed/simple; bh=5sgY48DeFt6LZVv6AA4skmGB5LL1KiEINGNQH9CCg1s=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=S11CO+XropRIQw1gASvzvdswpYuiMysFpIVhdNozLlGY/gZXe80jkRELiygxjjiCO5ygQsx0PiSUCaTYFerItNjNuxlsW5WSmAFqgXcOTshyHhR6zDAtN9dp3m7Eka0TvLvxWmcrSAL50jYlf9lFM33sYsr8WFa1j/lxbXTiIfw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fk840Rfp; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fk840Rfp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4657CC4CEF7; Mon, 29 Dec 2025 17:39:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767029956; bh=5sgY48DeFt6LZVv6AA4skmGB5LL1KiEINGNQH9CCg1s=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=fk840RfpFBaXBRJKCW1UPyDZzPN/FYE+rOEqTP1Zml7dhTvDHJ2APcZcOIEYLrfcx SAW/Pp91iph7HL/ONiixJej1ljpbESgiZCOh997uKjJLFcnGrshmwnj4hf9F56cnzY blDWNuJHOJ3BJudwrfp9mMYMnWThzQtdbhIDrI+DfEDJATKvJGkZP+uPzbwCGc3nTW pn8NzbIY+66LrUq3Wd+YCbwMtrOfEU7FHIxPBGKRksl3rWJiXsjO8Php/Yzr5qhzs9 +oLUTXVIBFQLU6CAHAeNtusQsy6/tku+2ynY2CkFCBJhhB7cWc/51/4xV60YPBj2oB l4UxRwJxkPNVg== Date: Mon, 29 Dec 2025 07:39:15 -1000 From: Tejun Heo To: Pavel Tikhomirov Cc: Johannes Weiner , Michal =?iso-8859-1?Q?Koutn=FD?= , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] cgroup-v2/freezer: Print information about unfreezable process Message-ID: References: <20251223102124.738818-1-ptikhomirov@virtuozzo.com> <20251223102124.738818-4-ptikhomirov@virtuozzo.com> <80d36215-de7e-448c-85ea-9e848496c210@virtuozzo.com> 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-Disposition: inline In-Reply-To: <80d36215-de7e-448c-85ea-9e848496c210@virtuozzo.com> Hello, On Mon, Dec 29, 2025 at 01:32:11PM +0800, Pavel Tikhomirov wrote: > > This is only suitable for debugging, and, for that, this can be done from > > userspace by walking the tasks and check /proc/PID/wchan. Should be > > do_freezer_trap for everything frozen. If something is not, read and dump > > its /proc/PID/stack. Wouldn't that work? > > Yes, I think that will do, Thanks. > > Though the trace printing in /proc/PID/stack is a bit less informative > than show_stack(), e.g. for my test module > (https://github.com/Snorch/proc-hang-module) the stack in /proc/PID/stack > will be just empty. (I guess it has to do with the fact that you need less > privileges to read /proc/PID/stack than dmesg, so you can do a more > informative thing in dmesg). You can use drgn, bpftrace or any other bpf tools to read way more detailed backtraces. Thanks. -- tejun