From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=193.142.43.55 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792494592; b=fHd2sBlQl5hPeIElJzqKyNIzJNPGitn5jGk6FCFsbDIHNRh/hiYdCtHq4lNk8nhH++TH +rL6ISwGtZGZ/4RHGeZMAgkwfg0D48VgqcmemrD3GM4tSymtS/yHJ/qdJ+iKGW+WLc+GV lm/dDY9ZHIHdfr1+deZOUlcJ1fe5xp8V2WlthKRtOPA8TMzVPey796yZl6j2r+8POdKla 7Nq+EsoW42wrbuuU/loUjwRoPMxiR7v16Sy59aVAVVuvdpCL8hebB0dFe2EeRzCHUlj6Q pMgNs/no+KSd52kTwMR8py9j6MuKw2pJKopHkXzeJFyEBGuhvW2ZmT46MDWse2Kr15A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792494592; h=DMARC-Filter:Date:DKIM-Signature:DKIM-Signature:From:To:Cc:Subject: Message-ID:References:MIME-Version:Content-Type:Content-Disposition: In-Reply-To; bh=qze9GsVDCuvc0w6qB++Wj9RPinmXFdwTA+6BdCxY1/M=; b=2vjUxvmemqAareqxSDmyXhGOZmtfwvq3eE63+/NdzljTIyAW+AQEjy3BEjYcxDG4HZl6 1r9Xg3c7oB7cT83dqW7CDtkLd3uuUpeg4A7iHWjfpCXwl5tfrj4s16kdn9Qo/FI4ekRi5 NtF3gGP1lvUFqONa1VRvFkMg4Zv3/uQpnp5AEhdJT6H/0PqhkB86FqdknZXSZEOVhYr63 IxuNmK65cWnJaJt4lrCqHYMGwidL/cyFVe9N/UTkWdnTPcXoNZcR0qRTfy0jcUA6FvXsl 9s8CAZcFcdkl2d/kMmKuTXhaC8wRO1JKot9JkSArBn1sYrgS9Nms4tbkh0vXTQsmp3w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass header.d=linutronix.de header.i=@linutronix.de header.a=rsa-sha256 header.s=2020 header.b=NmWXkX5k; dkim=pass header.d=linutronix.de header.i=@linutronix.de header.a=ed25519-sha256 header.s=2020e header.b=QaPbA8Nk; arc=none smtp.remote-ip=193.142.43.55 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7FF00606A323; Tue, 20 Oct 2026 11:09:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 7FF00606A323 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=linutronix.de header.i=@linutronix.de header.a=rsa-sha256 header.s=2020 header.b=NmWXkX5k; dkim=pass header.d=linutronix.de header.i=@linutronix.de header.a=ed25519-sha256 header.s=2020e header.b=QaPbA8Nk Date: Tue, 20 Oct 2026 13:09:48 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; 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=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-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: 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