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bh=IFdtle60mzH0ayotZck/6odceUOp5Nwjw33I6STHh1g=; b=bKkjdriAFUvo5SVW8HFrq8y+0G6k9p0VjXEz7q5GJJQICki43f6zAWz1OTRooO6ereqClP 6K/2BMErlay7pZK/4mjZVCsncr8o7gf8qw6yYoYDklWjBFBnlHXiRBL0qluGbqCS3NYLyW bMOWdceGbz0sV6k5JYgOFApqGK8VzSE= 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 134A91390C; Tue, 17 Jan 2023 15:42:22 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id TTlTBN7BxmOYVAAAMHmgww (envelope-from ); Tue, 17 Jan 2023 15:42:22 +0000 Date: Tue, 17 Jan 2023 16:42:21 +0100 From: Michal Hocko To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, michel@lespinasse.org, jglisse@google.com, vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, 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 26/41] kernel/fork: assert no VMA readers during its destruction Message-ID: References: <20230109205336.3665937-1-surenb@google.com> <20230109205336.3665937-27-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230109205336.3665937-27-surenb@google.com> X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: byprf55ijfxbtpgcuf3pxijj4o8bycjw X-Rspamd-Queue-Id: 05C7320013 X-HE-Tag: 1673970143-167364 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000006, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon 09-01-23 12:53:21, Suren Baghdasaryan wrote: > Assert there are no holders of VMA lock for reading when it is about to be > destroyed. > > Signed-off-by: Suren Baghdasaryan > --- > include/linux/mm.h | 8 ++++++++ > kernel/fork.c | 2 ++ > 2 files changed, 10 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 594e835bad9c..c464fc8a514c 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -680,6 +680,13 @@ static inline void vma_assert_write_locked(struct vm_area_struct *vma) > VM_BUG_ON_VMA(vma->vm_lock_seq != READ_ONCE(vma->vm_mm->mm_lock_seq), vma); > } > > +static inline void vma_assert_no_reader(struct vm_area_struct *vma) > +{ > + VM_BUG_ON_VMA(rwsem_is_locked(&vma->lock) && > + vma->vm_lock_seq != READ_ONCE(vma->vm_mm->mm_lock_seq), > + vma); Do we really need to check for vm_lock_seq? rwsem_is_locked should tell us something is wrong on its own, no? This could be somebody racing with the vma destruction and using the write lock. Unlikely but I do not see why to narrow debugging scope. -- Michal Hocko SUSE Labs