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Thu, 24 Apr 2025 14:45:40 -0700 (PDT) Date: Thu, 24 Apr 2025 17:45:37 -0400 From: Peter Xu To: Matthew Wilcox 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 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: -JfRix7Jv_lHIhBRgO9YQq_qjlUgQ1GDMZxaFC3kyu4_1745531141 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Queue-Id: 69C231C0004 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: gy63heh58c3z6n8u1c6zmefm686pyjds X-HE-Tag: 1745531143-997043 X-HE-Meta: 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 SFXf/Qhl Hg73kJTQIdrk0YOoGdSUqpJoocOO54ilLXWoPd+nzShTdHnxGDqVLa1DT/y8zkQjYv0Fk0Ay2eab/0ftZyprzVlvyttTRTofB4BSOZIC37lRSX4VLUVOYWS0dFC6Ag5JRqNfhqL/q4K5iziKJyPG3ANDPE/SYtN5KZ93eUk+JP6nFtn+OMItefgxw9zY5kCiHXPdadmeuisG2WaCYP0/3c1YPpN9FS/Ut2YXofSj/Ns7+55RaX4BtL8s2gEmI6uq85uGoMuVZdtIbfRlR15ktAdPxq7BEW2bHkLBF8jmO1RJJ7asIxDfD01NL8YhGDweawIIJl5K0NZwAzNo5INf8WoheBVdiF2JCF+Yn85OS4eECuUGhSub8/sLEUayGLLwookoE 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 08:42:00PM +0100, Matthew Wilcox wrote: > 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. Not really proposing that as I don't have a use caes. Just curious, could you explain a bit why having it interruptible is against the killable concept if (IIUC) it is still killable? Thanks, -- Peter Xu