perf_trace_buf_prepare() + perf_trace_buf_submit(task => NULL)
make no sense if hlist_empty(head). Change perf_trace_##call()
to check ->perf_events beforehand and do nothing if it is empty.
However, we can only do this if __task == NULL, so we also add
the __builtin_constant_p(__task) check.
Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
include/trace/ftrace.h | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 8886877..04455b8 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -663,6 +663,12 @@ perf_trace_##call(void *__data, proto)
\
int rctx; \
\
__data_size = ftrace_get_offsets_##call(&__data_offsets, args); \
+ \
+ head = this_cpu_ptr(event_call->perf_events); \
+ if (__builtin_constant_p(!__task) && !__task && \
+ hlist_empty(head)) \
+ return; \
+ \
__entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32),\
sizeof(u64)); \
__entry_size -= sizeof(u32); \
@@ -677,7 +683,6 @@ perf_trace_##call(void *__data, proto)
\
\
{ assign; } \
\
- head = this_cpu_ptr(event_call->perf_events); \
perf_trace_buf_submit(entry, __entry_size, rctx, __addr, \
__count, &__regs, head, __task); \
}
--
1.5.5.1
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