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[94.245.46.61]) by smtp.gmail.com with ESMTPSA id l8sm237631lfd.276.2021.01.20.08.22.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Jan 2021 08:22:01 -0800 (PST) From: "Uladzislau Rezki (Sony)" To: LKML , RCU , "Paul E . McKenney" , Michael Ellerman Cc: Andrew Morton , Daniel Axtens , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Peter Zijlstra , Michal Hocko , Thomas Gleixner , "Theodore Y . Ts'o" , Sebastian Andrzej Siewior , Uladzislau Rezki , Oleksiy Avramchenko Subject: [PATCH 3/3] kvfree_rcu: use migrate_disable/enable() Date: Wed, 20 Jan 2021 17:21:48 +0100 Message-Id: <20210120162148.1973-3-urezki@gmail.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210120162148.1973-1-urezki@gmail.com> References: <20210120162148.1973-1-urezki@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Since the page is obtained in a fully preemptible context, dropping the lock can lead to migration onto another CPU. As a result a prev. bnode of that CPU may be underutilised, because a decision has been made for a CPU that was run out of free slots to store a pointer. migrate_disable/enable() are now independent of RT, use it in order to prevent any migration during a page request for a specific CPU it is requested for. Signed-off-by: Uladzislau Rezki (Sony) --- kernel/rcu/tree.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 454809514c91..cad36074366d 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3489,10 +3489,12 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp, (*krcp)->bkvhead[idx]->nr_records == KVFREE_BULK_MAX_ENTR) { bnode = get_cached_bnode(*krcp); if (!bnode && can_alloc) { + migrate_disable(); krc_this_cpu_unlock(*krcp, *flags); bnode = (struct kvfree_rcu_bulk_data *) __get_free_page(GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOMEMALLOC | __GFP_NOWARN); *krcp = krc_this_cpu_lock(flags); + migrate_enable(); } if (!bnode) -- 2.20.1