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McKenney" , rcu@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 2/2] rcu: Dump vmalloc memory info safely Message-Id: <20230902182828.e42c6ec7b4a7beb1e4b2b042@linux-foundation.org> In-Reply-To: <20230830110402.386898-2-joel@joelfernandes.org> References: <20230830110402.386898-1-joel@joelfernandes.org> <20230830110402.386898-2-joel@joelfernandes.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: E9FE814001C X-Stat-Signature: o69wni3cbkjmus7tigy5bihh5scfkh78 X-Rspam-User: X-HE-Tag: 1693704512-531190 X-HE-Meta: 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 Wyl9MR/j I6TOsv0FwJ4lKaHeo8jhwPj3ye3mjC3ZLsQe+r4XXudLbaIcovl/TwgO4WqtDHW5G9X+ZxFeNZyjV0aBRaZk2hK407MjdvCZ89PZLu6bxfFYITalDLAvRT721psfWAeyeX4HX0U8fnL+vS0zXtO1CeautynS00YRBXdD9PxfrZriLH5gQIW87LQrAVheeGiA/k/n1+WTapNsiCEGE5IkbmClP+UWf3pCSCLixg/M6cJpdzLv6ttp3zUEDzFFpll1lzeajqscjoSTKrAyty1Ce5leESaQIKKYylHeFYyRsB7Hh0GIMUHqaRi8tNjI3T40h/aY1zmvhrk7tCuX6tqeTv8k7YOjyzKFjiLibkCiTX1zmpZLdu3EZOWf5Ic+3sHKxaCvkcwgGNQRR8IJcyLufrF4mfs1CKCmDGtlR7+z8hCLi1pRdZtmJh2ulAefNf8DM5M/95jEO+YF3K5I= 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 Wed, 30 Aug 2023 11:04:00 +0000 "Joel Fernandes (Google)" wrote: > Currently, for double invoke call_rcu(), will dump rcu_head objects > memory info, if the objects is not allocated from the slab allocator, > the vmalloc_dump_obj() will be invoke and the vmap_area_lock spinlock > need to be held, since the call_rcu() can be invoked in interrupt context, > therefore, there is a possibility of spinlock deadlock scenarios. > > And in Preempt-RT kernel, the rcutorture test also trigger the following > lockdep warning: "possibility of deadlock" sounds like something -stable kernels would like to have fixed. Did you consider the desirability of a -stable backport? If so, are we able to identify a suitable Fixes: target?