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McKenney" Cc: SeongJae Park , Matthew Wilcox , akpm@linux-foundation.org, vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] mm/slab: break up RCU readers on SLAB_TYPESAFE_BY_RCU example code Date: Sat, 15 Apr 2023 03:23:05 +0000 Message-Id: <20230415032305.3860-1-sj@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230415030452.3223-1-sj@kernel.org> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: C05F410000E X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: n4j6j5hed9r8m7z93w8agtmtpkmbg6ia X-HE-Tag: 1681528989-952500 X-HE-Meta: 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 /qQPzG71 wrAt8lsoyCeOmh7xZ+xrQ2QfzCqyDayHm35YhHLWzARgEsdq7galKdO6gArVbamp9q2MsSwVK6Lixp3vevtDGegTEAbQVXOAuxJQrp7ECyOgUJ5tSF423wSPDJGQeAxaOubAvjFtfF2UQFZjwspLdiO80Z9xemmRUwlYun8IktOuG+y2uJedFek9AohsCnrSoqyp5HByF2+r11X79FQOHnE8RjCmpS1WIIfCD4bl8mqtGKVcahMeRgrBVhK4/B9L2cOEL3aiIvt8a6t1qysPYqTxc6DQv6p2AbZYyKyBDY94tEnmTWZ9zt7HKn+V8yp49cr29ymT4Wi8qZB0/VLRj+1Vo8RX5gL/WQghkXDR4h9wIZJ0bjw61l8yEU9x++2l7H6Wrv1obymn4HI2PnkZ54Kybuy8OG5n5gJAAiAzKyCdaWSZIK/+dMjjuvTjTw2d7KQZoJlQpOSQZpOk= 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: On Sat, 15 Apr 2023 03:04:52 +0000 SeongJae Park wrote: > On Sat, 15 Apr 2023 03:51:54 +0100 Matthew Wilcox wrote: > > > On Sat, Apr 15, 2023 at 12:37:53AM +0000, SeongJae Park wrote: > > > * > > > + * begin: > > > * rcu_read_lock(); > > > - * again: > > > * obj = lockless_lookup(key); > > > * if (obj) { > > > * if (!try_get_ref(obj)) // might fail for free objects > > > - * goto again; > > > + * goto begin; I simply followed the commit da82af04352b ("doc: Update and wordsmith rculist_nulls.rst") for this change, and I think I overlooked this part. If I'm not missing something, I think we should call rcu_read_unlock() here too, just before 'goto begin'. I will post another patch for rculist_null.rst later. Thanks, SJ > > > * > > > * if (obj->key != key) { // not the object we expected > > > * put_ref(obj); > > > + * rcu_read_unlock(); > > > * goto again; > > > > - * goto again; > > + * goto begin; > > Oops, thank you for catching, Matthew! > > > Thanks, > SJ