tracing/function: Avoid perf_trace_buf_*() if event_function.perf_events is empty (b8ebfd3f) · Commits · e / devices / android_kernel_oneplus_sm7250

perf_trace_buf_prepare() + perf_trace_buf_submit(head, task => NULL) make no sense if hlist_empty(head). Change perf_ftrace_function_call() to check event_function.perf_events beforehand. Link: http://lkml.kernel.org/r/20130617170204.GA19803@redhat.com Acked-by:

Peter Zijlstra <peterz@infradead.org> Signed-off-by:

Oleg Nesterov <oleg@redhat.com> Signed-off-by:

Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_event_perf.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -266,6 +266,10 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
		struct pt_regs regs;
		int rctx;

		head = this_cpu_ptr(event_function.perf_events);
		if (hlist_empty(head))
		return;

		#define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \
		sizeof(u64)) - sizeof(u32))

		@@ -279,8 +283,6 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,

		entry->ip = ip;
		entry->parent_ip = parent_ip;

		head = this_cpu_ptr(event_function.perf_events);
		perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, 0,
		1, &regs, head, NULL);