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[142.68.57.212]) by smtp.gmail.com with ESMTPSA id p25sm312216qkm.97.2020.03.18.05.13.26 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 18 Mar 2020 05:13:26 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1jEXZe-0003a7-6B; Wed, 18 Mar 2020 09:13:26 -0300 Date: Wed, 18 Mar 2020 09:13:26 -0300 From: Jason Gunthorpe To: Qian Cai Cc: akpm@linux-foundation.org, paulmck@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/mmu_notifier: silence PROVE_RCU_LIST warnings Message-ID: <20200318121326.GZ20941@ziepe.ca> References: <20200317175640.2047-1-cai@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200317175640.2047-1-cai@lca.pw> User-Agent: Mutt/1.9.4 (2018-02-28) X-Bogosity: Ham, tests=bogofilter, spamicity=0.033458, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Mar 17, 2020 at 01:56:40PM -0400, Qian Cai wrote: > It is safe to traverse mm->notifier_subscriptions->list either under > SRCU read lock or mm->notifier_subscriptions->lock using > hlist_for_each_entry_rcu(). Silence the PROVE_RCU_LIST false positives, > for example, > > WARNING: suspicious RCU usage > ----------------------------- > mm/mmu_notifier.c:484 RCU-list traversed in non-reader section!! > > other info that might help us debug this: > > rcu_scheduler_active = 2, debug_locks = 1 > 3 locks held by libvirtd/802: > #0: ffff9321e3f58148 (&mm->mmap_sem#2){++++}, at: do_mprotect_pkey+0xe1/0x3e0 > #1: ffffffff91ae6160 (mmu_notifier_invalidate_range_start){+.+.}, at: change_p4d_range+0x5fa/0x800 > #2: ffffffff91ae6e08 (srcu){....}, at: __mmu_notifier_invalidate_range_start+0x178/0x460 > > stack backtrace: > CPU: 7 PID: 802 Comm: libvirtd Tainted: G I 5.6.0-rc6-next-20200317+ #2 > Hardware name: HP ProLiant BL460c Gen8, BIOS I31 11/02/2014 > Call Trace: > dump_stack+0xa4/0xfe > lockdep_rcu_suspicious+0xeb/0xf5 > __mmu_notifier_invalidate_range_start+0x3ff/0x460 > change_p4d_range+0x746/0x800 > change_protection+0x1df/0x300 > mprotect_fixup+0x245/0x3e0 > do_mprotect_pkey+0x23b/0x3e0 > __x64_sys_mprotect+0x51/0x70 > do_syscall_64+0x91/0xae8 > entry_SYSCALL_64_after_hwframe+0x49/0xb3 > > Signed-off-by: Qian Cai > --- > mm/mmu_notifier.c | 27 ++++++++++++++++++--------- > 1 file changed, 18 insertions(+), 9 deletions(-) Looks right to me Reviewed-by: Jason Gunthorpe This was missed during testing because we don't run with PROVE_RCU_LIST enabled Jason