Re: [PATCH v3] perf/ftrace: Fix WARNING in __unregister_ftrace_function

[Rik van Riel]

On Wed, 2026-05-27 at 11:37 -0400, Steven Rostedt wrote:
> On Wed, 27 May 2026 11:13:01 -0400
> Rik van Riel <riel@xxxxxxxxxxx> wrote:
> 
> > perf_ftrace_function_unregister() unconditionally calls
> > unregister_ftrace_function() without checking whether the
> > ftrace_ops
> > was ever successfully registered. This triggers a WARN_ON in
> > __unregister_ftrace_function() when the ops doesn't have
> > FTRACE_OPS_FL_ENABLED set.
> > 
> > This can happen during perf_event_alloc() error cleanup when
> > perf_trace_destroy() is called via __free_event() on an event whose
> > ftrace_ops registration failed or was already torn down by
> > perf_try_init_event()'s err_destroy path.
> > 
> > The call path is:
> >   perf_event_alloc() error cleanup
> >     -> __free_event()
> >       -> event->destroy() [tp_perf_event_destroy]
> >         -> perf_trace_destroy()
> >           -> perf_trace_event_close()
> >             -> TRACE_REG_PERF_CLOSE
> >               -> perf_ftrace_function_unregister()
> >                 -> unregister_ftrace_function()
> >                   -> __unregister_ftrace_function()
> >                     -> WARN_ON(!(ops->flags &
> > FTRACE_OPS_FL_ENABLED))  
> > 
> > Fix this by checking FTRACE_OPS_FL_ENABLED before attempting to
> > unregister. If the ops is not enabled, just free the filter and
> > return success.
> > 
> > Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx>
> 
> Thanks Rik. Is this urgent where it should have a Fixes tag and Cc
> stable as well as be sent to Linus during the -rc release, or can it
> wait for the next merge window?
> 

I don't think this patch has any particular urgency.

It can go in using whatever flow is most convenient.

-- 
All Rights Reversed.