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Date:   Tue, 10 May 2022 10:31:52 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Andrii Nakryiko <andrii.nakryiko@gmail.com>,
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Subject: Re: [PATCH] sched/tracing: append prev_state to tp args instead
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On Tue, 10 May 2022 10:29:40 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> On Tue, May 10, 2022 at 09:01:22AM +0200, Peter Zijlstra wrote:
> > On Mon, May 09, 2022 at 12:32:31PM -0700, Andrii Nakryiko wrote:  
> > > So can this patch be applied, please, or it's a hard no?  
> > 
> > Sorry; I got distracted with other work. I'll grudingly apply the patch.  
> 
>   gcc-11-i386-allmodconfig [15:35]  FAILED
>   | In file included from ../include/trace/define_custom_trace.h:55,
>   |                  from ../samples/trace_events/trace_custom_sched.h:96,
>   |                  from ../samples/trace_events/trace_custom_sched.c:24:
>   | ../samples/trace_events/./trace_custom_sched.h: In function ‘ftrace_test_custom_probe_sched_switch’:
>   | ../include/trace/trace_custom_events.h:178:42: error: passing argument 1 of ‘check_trace_callback_type_sched_switch’ from incompatible pointer type [-Werror=incompatible-pointer-types]
>   |   178 |         check_trace_callback_type_##call(trace_custom_event_raw_event_##template); \
>   |       |                                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   |       |                                          |
>   |       |                                          void (*)(void *, bool,  unsigned int,  struct task_struct *, struct task_struct *) {aka void (*)(void *, _Bool,  unsigned int,  struct task_struct *, struct task_struct *)}
>   | ../include/trace/trace_custom_events.h:34:9: note: in expansion of macro ‘DEFINE_CUSTOM_EVENT’
>   |    34 |         DEFINE_CUSTOM_EVENT(name, name, PARAMS(proto), PARAMS(args));


Yes, the custom tracepoint sample code uses the sched_switch tracepoint as
an example. That sample code needs to be updated:

In samples/trace_events/trace_custom_sched.h:

TRACE_CUSTOM_EVENT(sched_switch,

        /*
         * The TP_PROTO() and TP_ARGS must match the trace event
         * that the custom event is using.
         */
        TP_PROTO(bool preempt,
                 unsigned int prev_state,
                 struct task_struct *prev,
                 struct task_struct *next),

        TP_ARGS(preempt, prev_state, prev, next),


The arguments need to be updated.

-- Steve