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Tue, 18 Aug 2026 22:19:05 +0000 X-Migadu-Flow: FLOW_OUT From: Lance Yang To: david@kernel.org, mhocko@suse.com, akpm@linux-foundation.org Cc: leon.hwang@linux.dev, linux-mm@kvack.org, muchun.song@linux.dev, osalvador@suse.de, linux-kernel@vger.kernel.org, Lance Yang Subject: Re: [PATCH] hugetlb: add cond_resched() to __unmap_hugepage_range() Date: Wed, 19 Aug 2026 06:18:58 +0800 Message-Id: <20260818221858.86452-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <20260818115526.654d7311366b66cd031c67e4@linux-foundation.org> References: <20260818115526.654d7311366b66cd031c67e4@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: 1ih9rn6dnxgmobsam5653ny4hrzixwk6 X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 0E5D3120002 X-HE-Tag: 1787091556-166333 X-HE-Meta: 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 PPAYv6W1 Yw38beqZoKthuJe36/2GmwUd/DyETQ8JlRX6k5TZ3ghct+N6BS0Trd2XGz9GkIJXTwqxBN+3Mia+CM/fyt+PQOxSkfWLWINSGjfCmROwDOgqk3ExUrUW71qv3hTE+gQA3hFqpeW7WhBpm0nIntXjgUI47zkCSiV4o9jr5eqpbqcvLIPRxVB1gGDiDAfWioCcwvjQ5cQgDJfZzHroGBm0oIZUz7uP+yZK/PjrlMABjvtzyTmgBS01gLHzUIeyh1F10pOJtRDCPKRSK5KylIC12Qf4JTisbTjcpAjArODTivpG+1794oyDtF2cjvw/+NlcO6T1eH+yDRgo4G9lzzUdnnRxt+ShnuxHAfFRv Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: +Cc Michal On Tue, Aug 18, 2026 at 11:55:26AM -0700, Andrew Morton wrote: >On Tue, 18 Aug 2026 20:21:37 +0200 "David Hildenbrand (Arm)" wrote: > >> >>> if (!ptep) { >> >>> address |= last_addr_mask; >> >> >> >> As Michal just put it: >> >> >> >> "PREEMPT_NONE is effectivelly dead and most cond_resched will/should be >> >> removed. Is there any reason why you are not using full preemption when >> >> requiring low latencies?" >> >> >> >> https://lore.kernel.org/r/aoRnUxUlgf_kRlm8@tiehlicka Ah, I missed that PREEMPT_LAZY is now the default on major archs and PREEMPT_NONE is effectively gone there ... >> > >> > 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? Mainline scheduling stays unchanged, and stable can pick it up for old PREEMPT_NONE kernels. wdyt? Thanks, Lance