From nobody Fri Dec 19 19:07:41 2025 Received: from out-170.mta0.migadu.com (out-170.mta0.migadu.com [91.218.175.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DD28928C5BF for ; Wed, 14 May 2025 18:42:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.170 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747248171; cv=none; b=dVdo+yOl2dPKs2QkBy71T+x1ffVdHD2jTk0yAqxkL88KCap+z3xbe1cFghoHEDuYTmoAqH6QNXDGBA9RBKjtxhfFjjpYJxUBGzK9l6zDG13SYsMJga0Gfz7kWAVG1Y5za/BpKXdp7f+AzmtXUCcB0Ht2QNAd1yYZLXk1xSR6YUs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747248171; c=relaxed/simple; bh=F3WEBTPiQLWz9cCb+hjP8Ux7u/ANXbxtzcyn85cfhmw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Sb0yatj5dzMu439A++76SXXUu/R9u6W1rZzOAUehqWRRfyydNMhS3tUsjg9ZCAlCKNGuOSWfFiVdnyeI4NKe92aa43dprk7w3dUK54sRp5L9eFu03w0yE3w5oMxqQLmGuX2KtTuQ7AqnfkDjWCkd1y8Hh+NdIuueVEH62n5l6QI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=XsH+sSP2; arc=none smtp.client-ip=91.218.175.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="XsH+sSP2" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1747248167; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tl4rUg93LkTokTk1IS4m9ISxrd6enFA07YnhN9En2KU=; b=XsH+sSP2IqgV4b7JFzKmne3RJ7B8fs6sll5nB5jaO2ynnf01GgAFSgEyNXGG86e9Z7QQ1C xAVYpXslEoie+4agb0gtbili30uXYuaShK5I8zmCyUoS39PXhQWaMMqSpDmDEFLEr7kO7A tKA3XPMFfwrhihunQK+imHxFUbmwrx0= From: Shakeel Butt To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Vlastimil Babka , Alexei Starovoitov , Sebastian Andrzej Siewior , Harry Yoo , Yosry Ahmed , bpf@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: [PATCH v2 6/7] memcg: no stock lock for cpu hot-unplug Date: Wed, 14 May 2025 11:41:57 -0700 Message-ID: <20250514184158.3471331-7-shakeel.butt@linux.dev> In-Reply-To: <20250514184158.3471331-1-shakeel.butt@linux.dev> References: <20250514184158.3471331-1-shakeel.butt@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" Previously on the cpu hot-unplug, the kernel would call drain_obj_stock() with objcg local lock. However local lock was not needed as the stock which was accessed belongs to a dead cpu but we kept it there to disable irqs as drain_obj_stock() may call mod_objcg_mlstate() which required irqs disabled. However there is no need to disable irqs now for mod_objcg_mlstate(), so we can remove the local lock altogether from cpu hot-unplug path. Signed-off-by: Shakeel Butt Acked-by: Vlastimil Babka --- mm/memcontrol.c | 11 +---------- 1 file changed, 1 insertion(+), 10 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 1071db0b1df8..04d756be708b 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2025,17 +2025,8 @@ void drain_all_stock(struct mem_cgroup *root_memcg) =20 static int memcg_hotplug_cpu_dead(unsigned int cpu) { - struct obj_stock_pcp *obj_st; - unsigned long flags; - - obj_st =3D &per_cpu(obj_stock, cpu); - - /* drain_obj_stock requires objstock.lock */ - local_lock_irqsave(&obj_stock.lock, flags); - drain_obj_stock(obj_st); - local_unlock_irqrestore(&obj_stock.lock, flags); - /* no need for the local lock */ + drain_obj_stock(&per_cpu(obj_stock, cpu)); drain_stock_fully(&per_cpu(memcg_stock, cpu)); =20 return 0; --=20 2.47.1