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From: Amol Grover <frextrite@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>
Cc: "Paul E . McKenney" <paulmck@kernel.org>,
	linux-kernel@vger.kernel.org,
	Joel Fernandes <joel@joelfernandes.org>,
	linux-kernel-mentees@lists.linuxfoundation.org
Subject: [Linux-kernel-mentees] [PATCH 2/2] events: callchain: Use RCU API to access RCU pointer
Date: Wed, 29 Jan 2020 21:38:13 +0530	[thread overview]
Message-ID: <20200129160813.14263-2-frextrite@gmail.com> (raw)
In-Reply-To: <20200129160813.14263-1-frextrite@gmail.com>

callchain_cpus_entries is annotated as an RCU pointer.
Hence rcu_dereference_protected or similar RCU API is
required to dereference the pointer.

This fixes the following sparse warning
kernel/events/callchain.c:65:17: warning: incorrect type in assignment

Signed-off-by: Amol Grover <frextrite@gmail.com>
---
 kernel/events/callchain.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index f91e1f41d25d..a672d02a1b3a 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -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

_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

WARNING: multiple messages have this Message-ID (diff)
From: Amol Grover <frextrite@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>
Cc: linux-kernel@vger.kernel.org,
	linux-kernel-mentees@lists.linuxfoundation.org,
	Joel Fernandes <joel@joelfernandes.org>,
	Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	Amol Grover <frextrite@gmail.com>
Subject: [PATCH 2/2] events: callchain: Use RCU API to access RCU pointer
Date: Wed, 29 Jan 2020 21:38:13 +0530	[thread overview]
Message-ID: <20200129160813.14263-2-frextrite@gmail.com> (raw)
In-Reply-To: <20200129160813.14263-1-frextrite@gmail.com>

callchain_cpus_entries is annotated as an RCU pointer.
Hence rcu_dereference_protected or similar RCU API is
required to dereference the pointer.

This fixes the following sparse warning
kernel/events/callchain.c:65:17: warning: incorrect type in assignment

Signed-off-by: Amol Grover <frextrite@gmail.com>
---
 kernel/events/callchain.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index f91e1f41d25d..a672d02a1b3a 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -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


  reply	other threads:[~2020-01-29 16:10 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-29 16:08 [Linux-kernel-mentees] [PATCH 1/2] events: callchain: Annotate RCU pointer with __rcu Amol Grover
2020-01-29 16:08 ` Amol Grover
2020-01-29 16:08 ` Amol Grover [this message]
2020-01-29 16:08   ` [PATCH 2/2] events: callchain: Use RCU API to access RCU pointer Amol Grover
2020-01-29 22:19   ` [Linux-kernel-mentees] " Joel Fernandes
2020-01-29 22:19     ` Joel Fernandes
2020-01-30  8:23     ` [Linux-kernel-mentees] " Peter Zijlstra
2020-01-30  8:23       ` Peter Zijlstra
2020-01-30 10:14       ` [Linux-kernel-mentees] " Amol Grover
2020-01-30 10:14         ` Amol Grover
2020-01-30 13:32         ` [Linux-kernel-mentees] " Peter Zijlstra
2020-01-30 13:32           ` Peter Zijlstra
2020-01-29 22:19 ` [Linux-kernel-mentees] [PATCH 1/2] events: callchain: Annotate RCU pointer with __rcu Joel Fernandes
2020-01-29 22:19   ` Joel Fernandes

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