clang-9 does not like the way that the is_signed_type() compares
function pointers deep inside of the trace even macros:

In file included from arch/x86/xen/trace.c:21:
In file included from include/trace/events/xen.h:475:
In file included from include/trace/define_trace.h:102:
In file included from include/trace/trace_events.h:467:
include/trace/events/xen.h:69:7: error: ordered comparison of function pointers 
('xen_mc_callback_fn_t' (aka 'void (*)(void *)') and 'xen_mc_callback_fn_t') 
                    __field(xen_mc_callback_fn_t, fn)
include/trace/trace_events.h:415:29: note: expanded from macro '__field'
 #define __field(type, item)     __field_ext(type, item, FILTER_OTHER)
include/trace/trace_events.h:401:6: note: expanded from macro '__field_ext'
                                 is_signed_type(type), filter_type);    \
include/linux/trace_events.h:540:44: note: expanded from macro 'is_signed_type'
 #define is_signed_type(type)    (((type)(-1)) < (type)1)
note: (skipping 1 expansions in backtrace; use -fmacro-backtrace-limit=0 to see 
include/trace/trace_events.h:77:16: note: expanded from macro 'TRACE_EVENT'
                             PARAMS(tstruct),                  \
include/linux/tracepoint.h:95:25: note: expanded from macro 'PARAMS'
 #define PARAMS(args...) args
include/trace/trace_events.h:455:2: note: expanded from macro 
        tstruct;                                                        \

I guess the warning is reasonable in principle, though this seems to
be the only instance we get in the entire kernel today.
Shut up the warning by making it a void pointer in the exported

Fixes: c796f213a693 ("xen/trace: add multicall tracing")
Signed-off-by: Arnd Bergmann <>
 include/trace/events/xen.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/trace/events/xen.h b/include/trace/events/xen.h
index 9a0e8af21310..f75b77414ac1 100644
--- a/include/trace/events/xen.h
+++ b/include/trace/events/xen.h
@@ -66,7 +66,7 @@ TRACE_EVENT(xen_mc_callback,
            TP_PROTO(xen_mc_callback_fn_t fn, void *data),
            TP_ARGS(fn, data),
-                   __field(xen_mc_callback_fn_t, fn)
+                   __field(void *, fn)
                    __field(void *, data)

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