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Wed, 03 Sep 2025 09:15:19 -0700 (PDT) Date: Wed, 3 Sep 2025 12:15:17 -0400 From: Yury Norov To: Christian Loehle Cc: Peter Zijlstra , Dietmar Eggemann , Mark Rutland , Thomas Gleixner , "linux-kernel@vger.kernel.org" , Juri Lelli , Valentin Schneider Subject: Re: PATCH] sched: Fix sched_numa_find_nth_cpu() if mask offline Message-ID: References: <1ae868cf-470b-44d8-bda3-20a64dedd8b8@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1ae868cf-470b-44d8-bda3-20a64dedd8b8@arm.com> On Wed, Sep 03, 2025 at 04:48:32PM +0100, Christian Loehle wrote: > sched_numa_find_nth_cpu() uses a bsearch to look for the 'closest' > CPU in sched_domains_numa_masks and given cpus mask. However they > might not intersect if all CPUs in the cpus mask are offline. bsearch > will return NULL in that case, bail out instead of dereferencing a > bogus pointer. > > The previous behaviour lead to this bug when using maxcpus=4 on an > rk3399 (LLLLbb) (i.e. booting with all big CPUs offline): Thanks! Scheduling for -rc5.