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McKenney" , Amol Grover Subject: [PATCH v2] callchain: Annotate RCU pointer with __rcu Date: Thu, 30 Jan 2020 19:48:19 +0530 Message-Id: <20200130141818.18391-1-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 Fixes following instances of sparse error error: incompatible types in comparison expression (different address spaces) kernel/events/callchain.c:66:9: error: incompatible types in comparison kernel/events/callchain.c:96:9: error: incompatible types in comparison kernel/events/callchain.c:161:19: error: incompatible types in comparison This introduces the following warning kernel/events/callchain.c:65:17: warning: incorrect type in assignment which is fixed as below callchain_cpus_entries is annotated as an RCU pointer. Hence rcu_dereference_protected or similar RCU API is required to dereference the pointer. Signed-off-by: Amol Grover --- v2: - Squash both the commits into a single one. kernel/events/callchain.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c index c2b41a263166..a672d02a1b3a 100644 --- a/kernel/events/callchain.c +++ b/kernel/events/callchain.c @@ -32,7 +32,7 @@ static inline size_t perf_callchain_entry__sizeof(void) static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]); static atomic_t nr_callchain_events; static DEFINE_MUTEX(callchain_mutex); -static struct callchain_cpus_entries *callchain_cpus_entries; +static struct callchain_cpus_entries __rcu *callchain_cpus_entries; __weak void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, @@ -62,7 +62,8 @@ static void release_callchain_buffers(void) { struct callchain_cpus_entries *entries; - entries = callchain_cpus_entries; + entries = rcu_dereference_protected(callchain_cpus_entries, + lockdep_is_held(&callchain_mutex)); RCU_INIT_POINTER(callchain_cpus_entries, NULL); call_rcu(&entries->rcu_head, release_callchain_buffers_rcu); } -- 2.24.1