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[209.85.167.42]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-536870966c9sm1434919e87.149.2024.09.18.00.06.40 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 Sep 2024 00:06:41 -0700 (PDT) Received: by mail-lf1-f42.google.com with SMTP id 2adb3069b0e04-5365c512b00so7540267e87.3 for ; Wed, 18 Sep 2024 00:06:40 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCXMHPplJ1rVIKxTiPCOUXLxBYsxT/UuZ53QsbrEJYWlUxJGxoDHc31gMREwAR323elocAv6HmjUJQ==@kvack.org X-Received: by 2002:a05:6512:2208:b0:535:6986:9810 with SMTP id 2adb3069b0e04-53678feb164mr12882725e87.38.1726643199826; Wed, 18 Sep 2024 00:06:39 -0700 (PDT) MIME-Version: 1.0 References: <8d6c5d10-5750-4472-858c-eadc105453be@suse.cz> In-Reply-To: <8d6c5d10-5750-4472-858c-eadc105453be@suse.cz> From: Linus Torvalds Date: Wed, 18 Sep 2024 09:06:23 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [GIT PULL] slab updates for 6.11 To: Vlastimil Babka Cc: David Rientjes , Christoph Lameter , Andrew Morton , "linux-mm@kvack.org" , LKML , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Christian Brauner , RCU , Shakeel Butt , "Uladzislau Rezki (Sony)" Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 3F2911C000D X-Stat-Signature: prp5pk3xkssn6icc4d6x3qq7swmimd9k X-Rspam-User: X-HE-Tag: 1726643204-773922 X-HE-Meta: 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 gZIMY3cX 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 16 Sept 2024 at 11:45, Vlastimil Babka wrote: > > There's a small conflict with the rcu tree: > https://lore.kernel.org/lkml/20240812124748.3725011b@canb.auug.org.au/ Hmm. The conflict resolution is trivial, but the code itself looks buggy. Look here, commit 2b55d6a42d14 ("rcu/kvfree: Add kvfree_rcu_barrier() API") makes kvfree_rcu_queue_batch() do this: bool queued = false; ... for (i = 0; i < KFREE_N_BATCHES; i++) { ... queued = queue_rcu_work(system_wq, &krwp->rcu_work); ... return queued; and note how that return value is completely nonsensical. It doesn't imply anything got queued. It's returning whether the *last* call to queue_rcu_work() resulted in queued work. There is no way the return value is meaningful that I can see, and honestly, that means that the code in kvfree_rcu_barrier() looks actively buggy, and at worst might be an endless loop Now, maybe there's some reason why the code works fine, but it looks really really wrong. Please fix. The fix might be either a big comment about why it's ok, or making the "queued" assignment be a '|=' instead, or perhaps breaking out of the loop on the first successful queueing, or whatever. But not this "randomly return _one_ value of many of the queuing success". I've merged this, but I expect this to be fixed. Linus