On Tue, 2013-08-27 at 16:08 -0400, Steven Rostedt wrote:
> On Tue, 27 Aug 2013 14:40:13 -0500
> Tom Zanussi <tom.zanu...@linux.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?
>
Yeah, I think that should be ok and there should be no need to delay
waiters for that mutex - I'll look at moving it out for the next
revision.
Thanks,
Tom
> -- Steve
>
>
> > }
> >
>
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