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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1u82SO-0000000D5lv-1gF8; Thu, 24 Apr 2025 19:42:00 +0000 Date: Thu, 24 Apr 2025 20:42:00 +0100 From: Matthew Wilcox To: Peter Xu Cc: Johannes Weiner , Jens Axboe , Andrew Morton , "linux-fsdevel@vger.kernel.org" , Linux-MM Subject: Re: [PATCH] mm/userfaultfd: prevent busy looping for tasks with signals pending Message-ID: References: <27c3a7f5-aad8-4f2a-a66e-ff5ae98f31eb@kernel.dk> <20250424140344.GA840@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: F16BE1A000A X-Stat-Signature: xzherrjwqjem9zgz1q65g8oy7j7rerak X-Rspam-User: X-HE-Tag: 1745523723-705313 X-HE-Meta: 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 Zeyg+J3O CVKftlQmTOddG65YAuKk+t/EthT6sE6HSteUif74cisGZf/MAW0vK1rr10sEePmiBKSncJliyKL71V+9fShKemMjWOQhLGVAb5Y2/yUWwOp+aaq7QkUXPPfjWXc3GJuAahkcvlZHM8pKxRYJ6vKkH72vVmB7cMqk4sUxWZtkflmVJYhPDo1tV7eXjGcmEP3jHZUqS49e+O1xjz96hQ/XcRo0tlLGvu9wLLogeXwq7WeKd2V0MgPEu5i6EtjcoIU7uWDJuLeWbXyd/90M= 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: List-Subscribe: List-Unsubscribe: On Thu, Apr 24, 2025 at 02:26:37PM -0400, Peter Xu wrote: > Secondly, userfaultfd is indeed the only consumer of > FAULT_FLAG_INTERRUPTIBLE but not necessary always in the future. While > this patch resolves it for userfaultfd, it might get caught again later if > something else in the kernel starts to respects the _INTERRUPTIBLE flag > request. For example, __folio_lock_or_retry() ignores that flag so far, > but logically it should obey too (with a folio_wait_locked_interruptible).. No. Hell, no. We don't want non-fatal signals being able to interrupt that. There's a reason we introduced killable as a concept in the first place.