From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A5D5F16E895 for ; Tue, 28 May 2024 14:19:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716905958; cv=none; b=r985iDd5Xg04D7ScRR6QRm28ICvuqYIxbSgGE899lCreyMdB6l31PBEX2oObadTF/oOasF7YPrMgdJ9r4OkQBwH/mSf4q2c1/Bp8S3ad87120han9IzT7ZxZ5kSoGA/wh9zD/8p79kW2kW+k6WLHQHRJLbxkkz7vNRiuMPiqtgE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716905958; c=relaxed/simple; bh=yuPDGgUn+VpqJiWJHL5pFexMSMO0h7DglLbUSyFNJ5Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=kNgTugJqAleSiPD/txaQhYMem040GMZbLAHAx/RBxRuDugDjl/Ytudhp8CMluCs69Mkd69Fb/iutLQylV3mSN8QXUNYTEMNRym666duUT6SPE+APg5ZGPDs7U2NTxnd0rLUx3dD3q/YmwNNLkfva2W0NPdQJhEYk0ROWfzpUC74= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=E7vgjl/V; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="E7vgjl/V" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 415C7C3277B; Tue, 28 May 2024 14:19:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1716905958; bh=yuPDGgUn+VpqJiWJHL5pFexMSMO0h7DglLbUSyFNJ5Y=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=E7vgjl/Vztm2dNd7g3fcwJZSC9bQIl/dDnx7qD4i9yL3YYEYfUFzGVIb4T0QZLi7z Vx9xUR7HGlRrdvVzyMrEPer5QIPqvdkKi9dE301/IWlqSdpQnmW424JRVgM7kEMX8Y TNvyBdnw0f+nA7QbJ5SIf34APGwvIYDlCtwcHugeNe3sJlInHH6YTzvXKUeAdCwi/C igx906FH1Nkgt+wKfaYxXdCicVg3vkdjqYMA1t7ZZRU5dvZAuyBaprkmHLS5LKCZkL qFVRMmiVYo+BwZkDbq9dVHaUWRO5OJW5FWHKFB5Rd4ydnnFTBTzDLrbzKiauxIYqvR Nnv6nB3VpWq8Q== Message-ID: <3f4c0d70-8689-40a9-b051-13d013c4f09c@kernel.org> Date: Tue, 28 May 2024 16:19:14 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] memcg: Remove the lockdep assert from __mod_objcg_mlstate(). Content-Language: en-US To: Sebastian Andrzej Siewior Cc: Shakeel Butt , Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Thomas Gleixner References: <20240528121928.i-Gu7Jvg@linutronix.de> <09e085bb-f09e-4901-a2dd-a0b789bb8a4d@kernel.org> <20240528134027.OxDASsS3@linutronix.de> <20240528141341.rz_rytN_@linutronix.de> From: "Vlastimil Babka (SUSE)" In-Reply-To: <20240528141341.rz_rytN_@linutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/28/24 4:13 PM, Sebastian Andrzej Siewior wrote: > The assert was introduced in the commit cited below as an insurance that > the semantic is the same after the local_irq_save() has been removed and > the function has been made static. > > The original requirement to disable interrupt was due the modification > of per-CPU counters which require interrupts to be disabled because the > counter update operation is not atomic and some of the counters are > updated from interrupt context. > > All callers of __mod_objcg_mlstate() acquire a lock > (memcg_stock.stock_lock) which disables interrupts on !PREEMPT_RT and > the lockdep assert is satisfied. On PREEMPT_RT the interrupts are not > disabled and the assert triggers. > > The safety of the counter update is already ensured by > VM_WARN_ON_IRQS_ENABLED() which is part of __mod_memcg_lruvec_state() and > does not require yet another check. > > Remove the lockdep assert from __mod_objcg_mlstate(). > > Fixes: 91882c1617c15 ("memcg: simple cleanup of stats update functions") > Link: https://lore.kernel.org/r/20240528121928.i-Gu7Jvg@linutronix.de > Signed-off-by: Sebastian Andrzej Siewior Acked-by: Vlastimil Babka mm-hotfixes as it's a rc1 regression > --- > On 2024-05-28 15:44:51 [+0200], Vlastimil Babka (SUSE) wrote: >> I think just s/memcg_stats_lock()/__mod_memcg_lruvec_state()/ in your >> phrasing, since we are removing the lockdep assert from path that calls >> __mod_memcg_lruvec_state() and not memcg_stats_lock()? >> Or am I missing something? > > Yeah, makes sense. > > mm/memcontrol.c | 2 -- > 1 file changed, 2 deletions(-) > > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -3147,8 +3147,6 @@ static inline void __mod_objcg_mlstate(s > struct mem_cgroup *memcg; > struct lruvec *lruvec; > > - lockdep_assert_irqs_disabled(); > - > rcu_read_lock(); > memcg = obj_cgroup_memcg(objcg); > lruvec = mem_cgroup_lruvec(memcg, pgdat);