From nobody Wed Dec 17 21:44:16 2025 Received: from out-189.mta1.migadu.com (out-189.mta1.migadu.com [95.215.58.189]) (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 ACAA26EB79 for ; Thu, 10 Apr 2025 21:06:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.189 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744319220; cv=none; b=IVQQy+fdJxk/7z/QY68aXoSqq8vaeC4XV7D6nJYDfOIuWCOJh+jipAwkTLPJD40LbrRzDbL+T72cZpgs+0S1NZVvHJV4FT86X3A63lImTKm1D4+ZJXlAFdid5IalipnHJxlXtEHWweq+YlqBVfnPdNpZDKV64wJGNypgIGC6A1A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744319220; c=relaxed/simple; bh=0DMtd8z4cVfG0P0JrHiZFJzYyiNvQeqDTmT2YCX5dzI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=KnpieKC56JllCmtU3qutjcK4k/pkh+RR9YlonOubNRvDLp2UVq5wFr88tQsZ0nBFqJMRNeM2x4lsoFgRVE1sD/cK/mJHIYC8LQ+oE3QHwlczMvDUpgT2t4WcOjwksKcAXNstFQLbZx+/I+HFW1W7LWUb7VtfrnGihU8CwmzBjhI= 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=Ode1u+//; arc=none smtp.client-ip=95.215.58.189 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="Ode1u+//" 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=1744319206; 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; bh=eqKHtHIKdZRFnIVHPqA+xldT1tQxP5YolVvro+sDJq8=; b=Ode1u+//ukIHUqPcNQtouHpRbufdKBk3KfzUHB5JsjsEMVMCVortoXL7MeQBO9APmXLg8J kcU/d4xYIS8p+PIAgS4vyn26X1t0BrOV2pCnpP80Hh6xL3weqrt+klui2Y5E7D3RbkdV1L +DBTQFXnjdOJH8zOkVmoP2fSb29t8DU= From: Shakeel Butt To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Yosry Ahmed , Waiman Long , Vlastimil Babka , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: [PATCH] memcg: decouple memcg_hotplug_cpu_dead from stock_lock Date: Thu, 10 Apr 2025 14:06:23 -0700 Message-ID: <20250410210623.1016767-1-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" The function memcg_hotplug_cpu_dead works on the stock of a remote dead CPU and drain_obj_stock works on the given stock instead of local stock, so there is no need to take local stock_lock anymore. Signed-off-by: Shakeel Butt Acked-by: Roman Gushchin --- mm/memcontrol.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index f23a4d0ad239..2178a051bd09 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1789,7 +1789,7 @@ static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_s= tock) =3D { }; static DEFINE_MUTEX(percpu_charge_mutex); =20 -static void drain_obj_stock(struct memcg_stock_pcp *stock); +static void __drain_obj_stock(struct memcg_stock_pcp *stock); static bool obj_stock_flush_required(struct memcg_stock_pcp *stock, struct mem_cgroup *root_memcg); =20 @@ -1873,7 +1873,7 @@ static void drain_local_stock(struct work_struct *dum= my) local_lock_irqsave(&memcg_stock.stock_lock, flags); =20 stock =3D this_cpu_ptr(&memcg_stock); - drain_obj_stock(stock); + __drain_obj_stock(stock); drain_stock(stock); clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags); =20 @@ -1964,10 +1964,10 @@ static int memcg_hotplug_cpu_dead(unsigned int cpu) =20 stock =3D &per_cpu(memcg_stock, cpu); =20 - /* drain_obj_stock requires stock_lock */ - local_lock_irqsave(&memcg_stock.stock_lock, flags); - drain_obj_stock(stock); - local_unlock_irqrestore(&memcg_stock.stock_lock, flags); + local_irq_save(flag); + /* stock of a remote dead cpu, no need for stock_lock. */ + __drain_obj_stock(stock); + local_irq_restore(flag); =20 drain_stock(stock); =20 @@ -2837,7 +2837,11 @@ static bool consume_obj_stock(struct obj_cgroup *obj= cg, unsigned int nr_bytes, return ret; } =20 -static void drain_obj_stock(struct memcg_stock_pcp *stock) +/* + * Works on the given stock. The callers are responsible for the proper lo= cking + * for the local or remote stocks. + */ +static void __drain_obj_stock(struct memcg_stock_pcp *stock) { struct obj_cgroup *old =3D READ_ONCE(stock->cached_objcg); =20 @@ -2925,7 +2929,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg= , unsigned int nr_bytes, =20 stock =3D this_cpu_ptr(&memcg_stock); if (READ_ONCE(stock->cached_objcg) !=3D objcg) { /* reset if necessary */ - drain_obj_stock(stock); + __drain_obj_stock(stock); obj_cgroup_get(objcg); stock->nr_bytes =3D atomic_read(&objcg->nr_charged_bytes) ? atomic_xchg(&objcg->nr_charged_bytes, 0) : 0; --=20 2.47.1