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Subject[PATCH] xen/trace: avoid clang warning on function pointers
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') [-Werror,-Wordered-compare-function-pointers]
__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 all)
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 'DECLARE_EVENT_CLASS'
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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