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Received: from willy by casper.infradead.org with local (Exim 4.99.1 #2 (Red Hat Linux)) id 1wwTVR-0000000Cmxv-0rwC; Tue, 18 Aug 2026 23:46:09 +0000 Date: Wed, 19 Aug 2026 00:46:09 +0100 From: Matthew Wilcox To: Andrew Morton Cc: Lance Yang , david@kernel.org, mhocko@suse.com, leon.hwang@linux.dev, linux-mm@kvack.org, muchun.song@linux.dev, osalvador@suse.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH] hugetlb: add cond_resched() to __unmap_hugepage_range() Message-ID: References: <20260818115526.654d7311366b66cd031c67e4@linux-foundation.org> <20260818221858.86452-1-lance.yang@linux.dev> <20260818162430.0a51522ac9bd671cce62650f@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260818162430.0a51522ac9bd671cce62650f@linux-foundation.org> X-Rspam-User: X-Stat-Signature: 1ijofrd6gg5n1n96jrj8h1t39egfoqcz X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: E95D1100005 X-HE-Tag: 1787096771-921225 X-HE-Meta: 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 T1a3hx+Q yzjWUQ/O8eWs8Eb7tbCYcBKtxOkzSvVshOiJWV14qq8fuMej5LDTQNQZei+3swHAqG6IsYKJNU5DKs+kYAsSUZLI9MBFwmiQ+v+g3t7jL5W5JP8yHErr0imw+ZSjZVzmqf5gz336WzEpkoDyZDnqH/2Af6K1g38ZBCoQvh8uU2uxrgXPXHqlroY9hzAaEk4v4MWNPvqZTgnvUymlfsPBadkRnNu3qhrDdbvnPqF9H8a0GiR/RcS46dvc9TiQ06K6YtrqlyuyX5qnrLpcw2EmEaTGEqBUK5UgkiSac Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Aug 18, 2026 at 04:24:30PM -0700, Andrew Morton wrote: > On Wed, 19 Aug 2026 06:18:58 +0800 Lance Yang wrote: > > > >> > > > >> > That's pretty bad behavior and we might want to fix it in earlier > > >> > kernels. Is PREEMPT_NONE effectively dead in 6.18.x and its > > >> > existing users? > > >> > > > >> > If yes, we do want to fix older kernels then we should merge this. > > >> > > > >> > > >> Okay, but that would be stable-only fixes? > > > > > >Not understanding. > > > > > >Maybe you refer to adding a patch to -stable but not to -linus? That's > > >against the -stable rules > > >(Documentation/process/stable-kernel-rules.rst). > > > > Since cond_resched() is a scheduling no-op under LAZY/FULL anyway (only > > the __might_resched() debug check remains), why not take this upstream > > with Cc: stable? > > I think so - as long as PREEPMT_NONE exists we should support it as > well as we can. If the day comes that PREEMPT_NONE is removed, then we > get to remove lots of cond_resched()s. mm/ has 200 of the things. > > > Mainline scheduling stays unchanged, and stable can pick it up for old > > PREEMPT_NONE kernels. wdyt? > > Addressing this issue in older kernels is another reason. That is not the direction that the scheduler developers wish us to take.