linux-kernel - Re: [PATCH v7 01/10] tracing: Add support for SOFT

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Date:	Tue, 27 Aug 2013 16:08:27 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Tom Zanussi <tom.zanussi@...ux.intel.com>
Cc:	masami.hiramatsu.pt@...achi.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 01/10] tracing: Add support for SOFT_DISABLE to
 syscall events

On Tue, 27 Aug 2013 14:40:13 -0500
Tom Zanussi <tom.zanussi@...ux.intel.com> wrote:

> @@ -415,9 +429,14 @@ static void unreg_event_syscall_enter(struct ftrace_event_file *file,
>  		return;
>  	mutex_lock(&syscall_trace_lock);
>  	tr->sys_refcount_enter--;
> -	clear_bit(num, tr->enabled_enter_syscalls);
> +	rcu_assign_pointer(tr->enter_syscall_files[num], NULL);
>  	if (!tr->sys_refcount_enter)
>  		unregister_trace_sys_enter(ftrace_syscall_enter, tr);
> +	/*
> +	 * Callers expect the event to be completely disabled on
> +	 * return, so wait for current handlers to finish.
> +	 */
> +	synchronize_sched();
>  	mutex_unlock(&syscall_trace_lock);
>  }
>  
> @@ -435,7 +454,7 @@ static int reg_event_syscall_exit(struct ftrace_event_file *file,
>  	if (!tr->sys_refcount_exit)
>  		ret = register_trace_sys_exit(ftrace_syscall_exit, tr);
>  	if (!ret) {
> -		set_bit(num, tr->enabled_exit_syscalls);
> +		rcu_assign_pointer(tr->exit_syscall_files[num], file);
>  		tr->sys_refcount_exit++;
>  	}
>  	mutex_unlock(&syscall_trace_lock);
> @@ -453,9 +472,14 @@ static void unreg_event_syscall_exit(struct ftrace_event_file *file,
>  		return;
>  	mutex_lock(&syscall_trace_lock);
>  	tr->sys_refcount_exit--;
> -	clear_bit(num, tr->enabled_exit_syscalls);
> +	rcu_assign_pointer(tr->exit_syscall_files[num], NULL);
>  	if (!tr->sys_refcount_exit)
>  		unregister_trace_sys_exit(ftrace_syscall_exit, tr);
> +	/*
> +	 * Callers expect the event to be completely disabled on
> +	 * return, so wait for current handlers to finish.
> +	 */
> +	synchronize_sched();
>  	mutex_unlock(&syscall_trace_lock);

Can we do the synchronize_sched() after the mutex unlock in these two
places?

-- Steve


>  }
>  

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