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McKenney" , Amol Grover Subject: [PATCH] perf_event: Annotate rb pointer with __rcu Date: Sun, 9 Feb 2020 15:55:31 +0530 Message-Id: <20200209102530.26115-1-frextrite@gmail.com> X-Mailer: git-send-email 2.24.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org perf_event::rb is used in RCU context, tell sparse about it aswell to eliminate false-positives. Fixes the following instances of sparse error: incompatible types in comparison expression (different address spaces) kernel/events/core.c:5596:9 kernel/events/core.c:5302:22 kernel/events/core.c:5438:14 kernel/events/core.c:5471:14 kernel/events/core.c:5528:14 kernel/events/core.c:5614:14 kernel/events/core.c:5627:14 kernel/events/core.c:7182:13 kernel/events/ring_buffer.c:169:14 kernel/events/ring_buffer.c:169:14 kernel/events/ring_buffer.c:169:14 This introduces the following 2 new sparse errors: kernel/events/core.c:7212:9 kernel/events/core.c:5749:31 which are fixed by using RCU primitives, rcu_dereference() and rcu_access_pointer() on perf_event::rb. Signed-off-by: Amol Grover --- include/linux/perf_event.h | 2 +- kernel/events/core.c | 5 +++-- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 6d4c22aee384..1691107d2800 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -694,7 +694,7 @@ struct perf_event { struct mutex mmap_mutex; atomic_t mmap_count; - struct ring_buffer *rb; + struct ring_buffer __rcu *rb; struct list_head rb_entry; unsigned long rcu_batches; int rcu_pending; diff --git a/kernel/events/core.c b/kernel/events/core.c index 2173c23c25b4..7b9411d21165 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5746,7 +5746,7 @@ static void perf_mmap_close(struct vm_area_struct *vma) * still restart the iteration to make sure we're not now * iterating the wrong list. */ - if (event->rb == rb) + if (rcu_access_pointer(event->rb) == rb) ring_buffer_attach(event, NULL); mutex_unlock(&event->mmap_mutex); @@ -7209,7 +7209,8 @@ static void perf_pmu_output_stop(struct perf_event *event) restart: rcu_read_lock(); - list_for_each_entry_rcu(iter, &event->rb->event_list, rb_entry) { + list_for_each_entry_rcu(iter, &rcu_dereference(event->rb)->event_list, + rb_entry) { /* * For per-CPU events, we need to make sure that neither they * nor their children are running; for cpu==-1 events it's -- 2.24.1