linux-kernel - Re: [RFC][PATCH 18/18 v2] ftrace/sched: Mark functions that are RCU unsafe

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Date:	Sat, 31 Aug 2013 13:01:58 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>
Subject: Re: [RFC][PATCH 18/18 v2] ftrace/sched: Mark functions that are RCU
 unsafe

On Sat, Aug 31, 2013 at 01:11:35AM -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
> 
> Some callbacks of the function tracer use rcu_read_lock(). This means that
> there's places that can not be traced because RCU is not tracking the CPU
> for various reasons (like NO_HZ_FULL and coming back from userspace).
> 
> Thes functions need to be marked so that callbacks that use RCU do not
> trace them.
> 
> Cc: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>

Acked-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

> ---
>  kernel/sched/core.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index b7c32cb..9bd2aea 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1440,6 +1440,7 @@ void scheduler_ipi(void)
>  	}
>  	irq_exit();
>  }
> +FTRACE_UNSAFE_RCU(scheduler_ipi);
> 
>  static void ttwu_queue_remote(struct task_struct *p, int cpu)
>  {
> @@ -3222,6 +3223,7 @@ int idle_cpu(int cpu)
> 
>  	return 1;
>  }
> +FTRACE_UNSAFE_RCU(idle_cpu);
> 
>  /**
>   * idle_task - return the idle task for a given cpu.
> -- 
> 1.7.10.4
> 
> 

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