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From: Joel Fernandes <joel@joelfernandes.org>
To: Amol Grover <frextrite@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-kernel-mentees@lists.linuxfoundation.org,
	linux-kernel@vger.kernel.org,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Ingo Molnar <mingo@redhat.com>,
	Namhyung Kim <namhyung@kernel.org>, Jiri Olsa <jolsa@redhat.com>
Subject: Re: [Linux-kernel-mentees] [PATCH 2/2] events: callchain: Use RCU API to access RCU pointer
Date: Wed, 29 Jan 2020 17:19:09 -0500	[thread overview]
Message-ID: <20200129221909.GA74354@google.com> (raw)
In-Reply-To: <20200129160813.14263-2-frextrite@gmail.com>

On Wed, Jan 29, 2020 at 09:38:13PM +0530, Amol Grover wrote:
> 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));


Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>

thanks,

 - Joel


>  	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: Joel Fernandes <joel@joelfernandes.org>
To: Amol Grover <frextrite@gmail.com>
Cc: 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>,
	linux-kernel@vger.kernel.org,
	linux-kernel-mentees@lists.linuxfoundation.org,
	Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>,
	"Paul E . McKenney" <paulmck@kernel.org>
Subject: Re: [PATCH 2/2] events: callchain: Use RCU API to access RCU pointer
Date: Wed, 29 Jan 2020 17:19:09 -0500	[thread overview]
Message-ID: <20200129221909.GA74354@google.com> (raw)
In-Reply-To: <20200129160813.14263-2-frextrite@gmail.com>

On Wed, Jan 29, 2020 at 09:38:13PM +0530, Amol Grover wrote:
> 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));


Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>

thanks,

 - Joel


>  	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 22:19 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 ` [Linux-kernel-mentees] [PATCH 2/2] events: callchain: Use RCU API to access RCU pointer Amol Grover
2020-01-29 16:08   ` Amol Grover
2020-01-29 22:19   ` Joel Fernandes [this message]
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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