From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 86C5A3F58E1; Thu, 20 Aug 2026 10:41:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787222483; cv=none; b=Rps8Bp7pMOXp2LYK3Vs2gU51ZS7kIbCGQZ7dmZ64M6saSkJWsJwjPYb2ZYaHNq/fw74rWwgG1hZ+Q4wZpzRTsSpDEkXU5KYOf347MCEkYgv65gVDimLO4F4U8UGxJsjWka/VkFqs6NOXzpMZ1DQK1xifGRAslbDhjlF7+0u3cyo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787222483; c=relaxed/simple; bh=TxptvlsWpoC3IHlBpWmv7Jr3XQBii5dXCz1Wf6tKYFI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=gNce2TFawv6h8XqIjulzjL8WS+CPCAnHhalZYD6ckJMD4DbCMk78UF/hrQI+LWX22HV4ac7/OMpwUswUTdtH1R7SCYhzdFbOgiZiVleUyo4pem348EwqdtQswtDTJvNZyO3prD3RVJUPuulzZFg+yrOKvk4FF8xOIjoqbUwlm6g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=IbDigmCb; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="IbDigmCb" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=4axu5f3ZFy9nhF6jr3ZiDEC2ngzj+j39W2+MyShgJZ0=; b=IbDigmCb7Shr+VIqVz4otAUxjN soxhTWg1bgmougR6KLxriKz4Rp5pFOUKZdCxYY5y1Ax1/MPtuy3ZdLyHPIZzWRU+Z4JO2DR2nxPZd XEi+UJP1rgA28s5wEfp1h8xUVjxEl25n4Z0zBjXyytg6DzeFfv3EShwLICDAVazmxf8wdYeLhz86p D7siufmLQ8bxz7GtDhW54QDyfsIR+M2wfwk1tw7Skjx1WaHP7c3fhM2WKdqTiabxXDEeziObnkdKb oJ38WwK0xgRQVjVbPz7Pau8Kn2ZqVjNMa1mjpv7leyVMYhc1wWc/A0ZP63K2xfvPXq9pzFKCNp1Zb 9drsCViQ==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.99.2 #2 (Red Hat Linux)) id 1wx0Cz-000000031rx-2y9m; Thu, 20 Aug 2026 10:41:17 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 1CACD3006FA; Thu, 20 Aug 2026 12:41:12 +0200 (CEST) Date: Thu, 20 Aug 2026 12:41:11 +0200 From: Peter Zijlstra To: Sergey Senozhatsky Cc: Miklos Szeredi , fuse-devel@lists.linux.dev, linux-kernel@vger.kernel.org, "Rafael J. Wysocki" , linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v2] fuse: permit freezing while waiting for request answer Message-ID: <20260820104111.GC1837346@noisy.programming.kicks-ass.net> References: <20260819023542.561653-1-senozhatsky@chromium.org> <20260820084933.GA4036497@noisy.programming.kicks-ass.net> <20260820091018.GA4120091@noisy.programming.kicks-ass.net> <20260820093402.GB1837346@noisy.programming.kicks-ass.net> 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: On Thu, Aug 20, 2026 at 06:47:03PM +0900, Sergey Senozhatsky wrote: > > PM_FREEZE_ME_LAST is going to be trouble I think, before long you'll > > need PM_FREEZE_ME_REALLY_LAST or somesuch nonsense. > > We probably need more than one, yeah. This doesn't take into consideration > relations between tasks within a priority group. If client A holds a lock > and enters freezer, and client B sleeps on that lock, then this group > cannot be suspended. We need clients to reach some freezer checkpoint, > instead of doing in-place freezing. > > > Using cgroups for this also doesn't sound right. > > This begins sounding pessimistic. > > cgroup-s sounded solid to me, because this moves all the clients to that > save freezer checkpoint when they don't hold any locks. The only > problem is that if a task never reaches "return from syscall" then > we fail suspend. (I'm only talking about user-space tasks here, in the > context of fuse or inotify.) Why don't cgroups sound right to you? The cgroup hierarchy is already a mess, and the more different things you want to stuff in there, the worse it gets. Also, I still have machines with CGROUP=n. Also, you'd be putting suspend success in the hands of userspace, that sounds like a mighty fail right there.