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Ts'o" To: Tetsuo Handa Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] random: fix possible sleeping allocation from irq context Message-ID: <20180425060017.GB3412@thunk.org> Mail-Followup-To: "Theodore Y. Ts'o" , Tetsuo Handa , linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20180424034138.23994-1-tytso@mit.edu> <201804250046.w3P0kgkd045841@www262.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201804250046.w3P0kgkd045841@www262.sakura.ne.jp> User-Agent: Mutt/1.9.5 (2018-04-13) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on imap.thunk.org); SAEximRunCond expanded to false Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Wed, Apr 25, 2018 at 09:46:42AM +0900, Tetsuo Handa wrote: > Theodore Ts\'o wrote: > > We can do a sleeping allocation from an irq context when CONFIG_NUMA > > is enabled. Fix this by initializing the NUMA crng instances in a > > workqueue. > > Offloading to workqueue context itself would be OK, > but this patch makes linux.git unbootable because > > if (crng == &primary_crng && crng_init < 2) { > invalidate_batched_entropy(); > numa_crng_init(); // <= Deferred to workqueue context. > crng_init = 2; // <= Not waiting for workqueue context, and oops before console becomes ready. ;-) > process_random_ready_list(); > wake_up_interruptible(&crng_init_wait); > pr_notice(\"random: crng init done\\n\"); > } > > Please don\'t pretend rng_ready() before workqueue context is processed. Where's the oops? It's not oopsing for me, and if the NUMA crng is not initailized, the code in extract_entropy returns falls back to using the primary_crng: static void extract_crng(__u32 out[CHACHA20_BLOCK_WORDS]) { struct crng_state *crng = NULL; #ifdef CONFIG_NUMA if (crng_node_pool) crng = crng_node_pool[numa_node_id()]; if (crng == NULL) #endif crng = &primary_crng; _extract_crng(crng, out); } - Ted