From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 441AEC25B50 for ; Mon, 23 Jan 2023 09:56:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6CAC96B0071; Mon, 23 Jan 2023 04:56:38 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 67A5C6B0072; Mon, 23 Jan 2023 04:56:38 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 51AC06B0073; Mon, 23 Jan 2023 04:56:38 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 3EDA46B0071 for ; Mon, 23 Jan 2023 04:56:38 -0500 (EST) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 13793C05F4 for ; Mon, 23 Jan 2023 09:56:38 +0000 (UTC) X-FDA: 80385609276.30.F823F39 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by imf14.hostedemail.com (Postfix) with ESMTP id 33473100018 for ; Mon, 23 Jan 2023 09:56:34 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=FDU+Yu+y; spf=pass (imf14.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1674467795; h=from:from:sender: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=23+bxvlDHhv98+IF5/OMG/D6ucEV8Wbm0GFOsBS724w=; b=KhEdD+acXBZwhUROfxCR4ZyWbwJJ5Zp9N3IywNQW+1xYMbCqdSAafzN/F9P2SRPqxhhcK1 FDYZ3ss5pEGvKWmwXYhEZR4L1uXo2I0IjPiMcmY7gIBGLfB2gG00deIxJ1rLvpULN1n809 dSLi09IHk4CA6GHpi21ekw0kCZ/nSQg= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=FDU+Yu+y; spf=pass (imf14.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1674467795; a=rsa-sha256; cv=none; b=rer1+iNLpt95bYgoe2PyEo5xTAMncMPdaMAZj+dQQPvyyfiZnL6Lt43cTai/3N9H+dTvPQ hEhsbl59chVLPYXOaHCt+gOSboGoAVpQ/5l/QJsD2ICYexO8rgKRCRTRd8Yt+s/wiX5JIe 4A9Q1FNERKfKv5Zib2uyEGuwHQnZ17o= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id D19401F461; Mon, 23 Jan 2023 09:56:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1674467793; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=23+bxvlDHhv98+IF5/OMG/D6ucEV8Wbm0GFOsBS724w=; b=FDU+Yu+yXPWSXaQUfLGbcbZhHPwb2qTY1gBoIfGCdb2MThCmusoz5gVarg1ZuhxgoeIHdz RmIhY+0GxEm+RBG/DSo975FXvYL1fOFO37wRXzIf+4R8Z5kAtfhbMIi0k/TOcjSLCGwPBv hGIJyY1EgNMwDPtsogvWoxt9MurAVsQ= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id A9002134F5; Mon, 23 Jan 2023 09:56:33 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id zZHYKNFZzmMjCgAAMHmgww (envelope-from ); Mon, 23 Jan 2023 09:56:33 +0000 Date: Mon, 23 Jan 2023 10:56:32 +0100 From: Michal Hocko To: Suren Baghdasaryan Cc: Matthew Wilcox , "Liam R. Howlett" , akpm@linux-foundation.org, michel@lespinasse.org, jglisse@google.com, vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net, dave@stgolabs.net, peterz@infradead.org, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, paulmck@kernel.org, luto@kernel.org, songliubraving@fb.com, peterx@redhat.com, david@redhat.com, dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de, kent.overstreet@linux.dev, punit.agrawal@bytedance.com, lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, jannh@google.com, shakeelb@google.com, tatashin@google.com, edumazet@google.com, gthelen@google.com, gurua@google.com, arjunroy@google.com, soheil@google.com, hughlynch@google.com, leewalsh@google.com, posk@google.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 39/41] kernel/fork: throttle call_rcu() calls in vm_area_free Message-ID: References: <20230120170815.yuylbs27r6xcjpq5@revolver> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 33473100018 X-Rspam-User: X-Stat-Signature: 6fqut9prujkxpztafsxg4nhjw7fjimd9 X-HE-Tag: 1674467794-97593 X-HE-Meta: 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 p2T42a9K wpdRRXiY/6EfIo56FnUi51/z3B/PrecXxwxoF/eLDF18roAFllIntm6mAhqAr9g/pM1HovrMyie60V7mzIfwm1lkF96J51TUUq+3MPCr7B7zrZ+R+y525dHQLe2+RepGakKlgghT0ogLDv9nasSxVlvxUinvFHtpqUl9thaE168/BE6+DDkDNHYRztC9usxMI6uuYTq0MXv33paqu/5Pa9KQU+e3t22l/somuFZK0tJ6cE07XHFtAygpSpMWqK2GUmb27SttKjroa9D+FCTH4YOlcBA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri 20-01-23 09:50:01, Suren Baghdasaryan wrote: > On Fri, Jan 20, 2023 at 9:32 AM Matthew Wilcox wrote: [...] > > The page fault handler (or whatever other reader -- ptrace, proc, etc) > > should have a refcount on the mm_struct, so we can't be in this path > > trying to free VMAs. Right? > > Hmm. That sounds right. I checked process_mrelease() as well, which > operated on mm with only mmgrab()+mmap_read_lock() but it only unmaps > VMAs without freeing them, so we are still good. Michal, do you agree > this is ok? Don't we need RCU procetions for the vma life time assurance? Jann has already shown how rwsem is not safe wrt to unlock and free without RCU. -- Michal Hocko SUSE Labs