tracing: make trace pipe recognize latency format flag (112f38a7) · Commits · 戴 / test

The trace_pipe did not recognize the latency format flag and would produce different output than the trace file. The problem was partly due that the trace flags in the iterator was not set as well as the trace_pipe zeros out part of the iterator (including the flags) to be able to use the same routines as the trace file. trace_flags of the iterator should not cause any problems when not zeroed out by for trace_pipe. Reported-by:

Johannes Berg <johannes@sipsolutions.net> Signed-off-by:

Steven Rostedt <rostedt@goodmis.org>

include/linux/ftrace_event.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -51,6 +51,7 @@ struct trace_iterator {
		int cpu_file;
		struct mutex mutex;
		struct ring_buffer_iter *buffer_iter[NR_CPUS];
		unsigned long iter_flags;

		/* The below is zeroed out in pipe_read */
		struct trace_seq seq;
		@@ -58,7 +59,6 @@ struct trace_iterator {
		int cpu;
		u64 ts;

		unsigned long iter_flags;
		loff_t pos;
		long idx;

kernel/trace/trace.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -2826,6 +2826,9 @@ static int tracing_open_pipe(struct inode inode, struct file filp)
		/* trace pipe does not show start of buffer */
		cpumask_setall(iter->started);

		if (trace_flags & TRACE_ITER_LATENCY_FMT)
		iter->iter_flags \|= TRACE_FILE_LAT_FMT;

		iter->cpu_file = cpu_file;
		iter->tr = &global_trace;
		mutex_init(&iter->mutex);

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