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,
Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
linux-kernel-mentees@lists.linuxfoundation.org
Subject: [Linux-kernel-mentees] [PATCH v2] callchain: Annotate RCU pointer with __rcu
Date: Thu, 30 Jan 2020 19:48:19 +0530 [thread overview]
Message-ID: <20200130141818.18391-1-frextrite@gmail.com> (raw)
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 <frextrite@gmail.com>
---
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
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next reply other threads:[~2020-01-30 14:23 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-30 14:18 Amol Grover [this message]
2020-02-14 18:20 ` [Linux-kernel-mentees] [PATCH v2] callchain: Annotate RCU pointer with __rcu Amol Grover
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