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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id c2-20020a170902d90200b001c7453fae33sm2161258plz.280.2023.11.08.14.16.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Nov 2023 14:16:25 -0800 (PST) Date: Wed, 8 Nov 2023 14:16:25 -0800 From: Kees Cook To: Steven Rostedt Cc: Ankur Arora , linux-kernel@vger.kernel.org, tglx@linutronix.de, peterz@infradead.org, torvalds@linux-foundation.org, paulmck@kernel.org, linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, willy@infradead.org, mgorman@suse.de, jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, jgross@suse.com, andrew.cooper3@citrix.com, mingo@kernel.org, bristot@kernel.org, mathieu.desnoyers@efficios.com, geert@linux-m68k.org, glaubitz@physik.fu-berlin.de, anton.ivanov@cambridgegreys.com, mattst88@gmail.com, krypton@ulrich-teichert.org, David.Laight@aculab.com, richard@nod.at, mjguzik@gmail.com, Herbert Xu , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Thomas Graf Subject: Re: [RFC PATCH 71/86] treewide: lib: remove cond_resched() Message-ID: <202311081415.C4774E1B@keescook> References: <20231107215742.363031-1-ankur.a.arora@oracle.com> <20231107230822.371443-1-ankur.a.arora@oracle.com> <20231107230822.371443-15-ankur.a.arora@oracle.com> <202311081114.0F15C1FB9@keescook> <20231108144144.3d257286@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231108144144.3d257286@gandalf.local.home> X-Rspamd-Queue-Id: CBE0EC001B X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 51xybd5nkj6eawb4pcubzu9qepwek7hj X-HE-Tag: 1699481787-836927 X-HE-Meta: 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 k0Ky1IkY uPMsss+NESbSDcM73sA3OLk8ttIPkK0zx/eyGIZ2g6OEyY4i0Tv3oK8xu5rNjkZI+m3cACNgTbgffXszfzwQecaGllDCTsKdpKdhNDkZqZ5LgxmjT5d87dShVjceOIOycxeeZyq+HmHy6dhUR8+qWOWzRjIlXXEzJaREO+ykyWZLeN3Z44iXnaq9RA8T1lVyFhPTF5lWiRmjIRY8AK7oVKCTXXZ5szQv6Yn7fHm+DUNHeWLdMNuCLy/3UYePs0w9rg4bZpBxbY55WbMCQuOVl06C9dsejLPaRVK4ZpVBPG2fzmgVoK3a24vSbCjo8AYtKp4kXyGDm7nn37Xgh+EJwiXW06mI5OVHnDUTkwsyGXlyOcI5Nv5ACcVXktGPY0+/jQHcvMLpi3e6QCP2d8ZpRY7ZOxgn44urMBB+Dh9lOv6tVKVu/208vV0MRjtMeHr4E5Hgag4yqcwBvb2U= 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 Wed, Nov 08, 2023 at 02:41:44PM -0500, Steven Rostedt wrote: > On Wed, 8 Nov 2023 11:15:37 -0800 > Kees Cook wrote: > > > FOr the memcpy_kunit.c cases, I don't think there are preemption > > locations in its loops. Perhaps I'm misunderstanding something? Why will > > the memcpy test no longer produce softlockup splats? > > This patchset will switch over to a NEED_RESCHED_LAZY routine, so that > VOLUNTARY and NONE preemption models will be forced to preempt if its in > the kernel for too long. > > Time slice is over: set NEED_RESCHED_LAZY > > For VOLUNTARY and NONE, NEED_RESCHED_LAZY will not preempt the kernel (but > will preempt user space). > > If in the kernel for over 1 tick (1ms for 1000Hz, 4ms for 250Hz, etc), > if NEED_RESCHED_LAZY is still set after one tick, then set NEED_RESCHED. > > NEED_RESCHED will now schedule in the kernel once it is able to regardless > of preemption model. (PREEMPT_NONE will now use preempt_disable()). > > This allows us to get rid of all cond_resched()s throughout the kernel as > this will be the new mechanism to keep from running inside the kernel for > too long. The watchdog is always longer than one tick. Okay, it sounds like it's taken care of. :) Acked-by: Kees Cook # for lib/memcpy_kunit.c -- Kees Cook