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h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qze9GsVDCuvc0w6qB++Wj9RPinmXFdwTA+6BdCxY1/M=; b=NmWXkX5kiRg47zHcScMu4FDG96YeUHWrE1RYjqbPrQ1ZhB5vy01TKBsfKFr5mFWCPBJ899 MDXKEuI2g2g0aBFfFdSOkXqkc+QgKfYcDd6jBbrQfr1Y6Z2jKBKS0JjQzxbtXc5FGYteby Z9JeX93y8BCaUd5vJpg4+9I3IYqT58hAikmwvmLgku0cyKEYCUCbCvENRTqqCHGPzWVRwX a2druN3/XV93Uc8a9HhNkFyJ9/Ufi0TS4H5g4h672pvjDvsTxQLJTL3B5/HLFa/iopNwuw BlPUlPEvgu97qvCqRqjQswP/pFcO5/0nooZPxNHGQIAyBLJXCClUO73jO2CZDg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1792494589; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qze9GsVDCuvc0w6qB++Wj9RPinmXFdwTA+6BdCxY1/M=; b=QaPbA8Nkwz1OAhyo1nPjOtN2F30jqrtsR5wGbN3Df2I5yvgZqmk1ZxKGT5qns2rGAB7zLC mM//MeqmqRVENJCg== From: Sebastian Andrzej Siewior To: "Vlastimil Babka (SUSE)" Cc: Karl Mehltretter , Andrew Morton , Alexei Starovoitov , Alexander Duyck , David Hildenbrand , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Shakeel Butt , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] mm/page_alloc: skip shuffling and reporting for no-lock frees Message-ID: <20261020110948.wv_yGAhQ@linutronix.de> References: <20261005063515.6312-1-kmehltretter@gmail.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: E795F4000B X-Stat-Signature: 6pz8eng3aopx3ikiqx3pf716pi8zjhmb X-Rspamd-Server: rspam04 X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1792494591-338074 X-HE-Meta: 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 w9flxH/Z psf7LX6EaVq1/vUnwNZK8yRFJwLCL9roXT196e14w3BKkbpFBEj8uf3cGC++CWwJl7Tjtug4AkbGWz4DVKNT0EAQBd/oysGHorziRWfTN8AXwogORXa7L1g8xtElCHCh7J7NZC/TauFH3nT8trLjP/wWsMmtz9iH/WGARI66S4j6jfcNvhKC77UwRWkqYu9aRGJWCh0DzQ7kira+iem3wdzF55aH246p6UBE6+pprccPb54tFkMUab/mSxQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 2026-10-20 12:02:01 [+0200], Vlastimil Babka (SUSE) wrote: > > An instrumented PREEMPT_RT lockdep run forced a random-bit cache refill > > while calling free_pages_nolock() under a raw spinlock. The unpatched > > allocator reported: > > > > BUG: Invalid wait context > > > > The attempted lock was batched_entropy_u64.lock in get_random_u64(). > > Lockdep showed the raw test lock and zone->lock both held. > > In slab we solved this by using prandom - commit a1e244a9f177 ("mm/slab: use > prandom if !allow_spin") > Could be better? I hated it at first but now that I looked longer at it, it is not that bad. Sebastian