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Fri, 10 Jul 2026 09:27:50 -0700 (PDT) Received: from ziepe.ca ([159.2.72.92]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8ffd50e081dsm44781476d6.9.2026.07.10.09.27.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Jul 2026 09:27:49 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wiE4r-00000007XPF-1WDC; Fri, 10 Jul 2026 13:27:49 -0300 Date: Fri, 10 Jul 2026 13:27:49 -0300 From: Jason Gunthorpe To: Stanislav Kinsburskii Cc: airlied@gmail.com, akhilesh@ee.iitb.ac.in, akpm@linux-foundation.org, corbet@lwn.net, dakr@kernel.org, david@kernel.org, decui@microsoft.com, haiyangz@microsoft.com, kees@kernel.org, kys@microsoft.com, leon@kernel.org, liam@infradead.org, lizhi.hou@amd.com, ljs@kernel.org, longli@microsoft.com, lyude@redhat.com, maarten.lankhorst@linux.intel.com, mamin506@gmail.com, mhocko@suse.com, mripard@kernel.org, nouveau@lists.freedesktop.org, ogabbay@kernel.org, oleg@redhat.com, rppt@kernel.org, shuah@kernel.org, simona@ffwll.ch, skhan@linuxfoundation.org, surenb@google.com, tzimmermann@suse.de, vbabka@kernel.org, wei.liu@kernel.org, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-rdma@vger.kernel.org Subject: Re: [PATCH v7 2/8] mm/hmm: add hmm_range_fault_unlocked_timeout() for mmap lock-drop support Message-ID: <20260710162749.GP118978@ziepe.ca> References: <178345345668.660027.2952911919681614557.stgit@skinsburskii> <178345362182.660027.12809852179204464964.stgit@skinsburskii> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <178345362182.660027.12809852179204464964.stgit@skinsburskii> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tue, Jul 07, 2026 at 12:47:01PM -0700, Stanislav Kinsburskii wrote: > +int hmm_range_fault_unlocked_timeout(struct hmm_range *range, > + unsigned long timeout) > +{ > + struct mm_struct *mm = range->notifier->mm; > + unsigned long deadline = 0; > + int locked, ret; > + > + if (timeout) > + deadline = jiffies + timeout; > + > + do { > + if (fatal_signal_pending(current)) > + return -EINTR; > + > + if (timeout && time_after(jiffies, deadline)) > + return -EBUSY; I really dislike there is a timeout here, HMM is supposed to be more deterministic. GUP doesn't have a timeout, what is this about? 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Fri, 10 Jul 2026 09:27:49 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wiE4r-00000007XPF-1WDC; Fri, 10 Jul 2026 13:27:49 -0300 Date: Fri, 10 Jul 2026 13:27:49 -0300 From: Jason Gunthorpe To: Stanislav Kinsburskii Subject: Re: [PATCH v7 2/8] mm/hmm: add hmm_range_fault_unlocked_timeout() for mmap lock-drop support Message-ID: <20260710162749.GP118978@ziepe.ca> References: <178345345668.660027.2952911919681614557.stgit@skinsburskii> <178345362182.660027.12809852179204464964.stgit@skinsburskii> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <178345362182.660027.12809852179204464964.stgit@skinsburskii> Message-ID-Hash: XOKVTRIIJBXXR7GXHJCSQOOBZMST6N6F X-Message-ID-Hash: XOKVTRIIJBXXR7GXHJCSQOOBZMST6N6F X-MailFrom: jgg@ziepe.ca X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: akhilesh@ee.iitb.ac.in, akpm@linux-foundation.org, corbet@lwn.net, dakr@kernel.org, david@kernel.org, decui@microsoft.com, haiyangz@microsoft.com, kees@kernel.org, kys@microsoft.com, leon@kernel.org, liam@infradead.org, lizhi.hou@amd.com, ljs@kernel.org, longli@microsoft.com, maarten.lankhorst@linux.intel.com, mamin506@gmail.com, mhocko@suse.com, mripard@kernel.org, nouveau@lists.freedesktop.org, ogabbay@kernel.org, oleg@redhat.com, rppt@kernel.org, shuah@kernel.org, simona@ffwll.ch, skhan@linuxfoundation.org, surenb@google.com, vbabka@kernel.org, wei.liu@kernel.org, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-rdma@vger.kernel.org X-Mailman-Version: 3.3.8 Precedence: list List-Id: Nouveau development list Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Tue, Jul 07, 2026 at 12:47:01PM -0700, Stanislav Kinsburskii wrote: > +int hmm_range_fault_unlocked_timeout(struct hmm_range *range, > + unsigned long timeout) > +{ > + struct mm_struct *mm = range->notifier->mm; > + unsigned long deadline = 0; > + int locked, ret; > + > + if (timeout) > + deadline = jiffies + timeout; > + > + do { > + if (fatal_signal_pending(current)) > + return -EINTR; > + > + if (timeout && time_after(jiffies, deadline)) > + return -EBUSY; I really dislike there is a timeout here, HMM is supposed to be more deterministic. GUP doesn't have a timeout, what is this about? Jason