ring_buffer: tracing: Inherit the tracing setting to next ring buffer

Maintain the tracing on/off setting of the ring_buffer when switching to the trace buffer snapshot. Taking a snapshot is done by swapping the backup ring buffer (max_tr_buffer). But since the tracing on/off setting is defined by the ring buffer, when swapping it, the tracing on/off setting can also be changed. This causes a strange result like below: /sys/kernel/debug/tracing # cat tracing_on 1 /sys/kernel/debug/tracing # echo 0 > tracing_on /sys/kernel/debug/tracing # cat tracing_on 0 /sys/kernel/debug/tracing # echo 1 > snapshot /sys/kernel/debug/tracing # cat tracing_on 1 /sys/kernel/debug/tracing # echo 1 > snapshot /sys/kernel/debug/tracing # cat tracing_on 0 We don't touch tracing_on, but snapshot changes tracing_on setting each time. This is an anomaly, because user doesn't know that each "ring_buffer" stores its own tracing-enable state and the snapshot is done by swapping ring buffers. Link: http://lkml.kernel.org/r/153149929558.11274.11730609978254724394.stgit@devbox

Masami Hiramatsu committed 8 years ago

Commit 73c8d891 parent 1863c383 files · +23 −0Browse files

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include/linux/ring_buffer.h+1−0

@@ -165,6 +165,7 @@ void ring_buffer_record_enable(struct ring_buffer *buffer); · 164 unmodified lines
165	165	void ring_buffer_record_off(struct ring_buffer *buffer);
166	166	void ring_buffer_record_on(struct ring_buffer *buffer);
167	167	int ring_buffer_record_is_on(struct ring_buffer *buffer);
	168	+int ring_buffer_record_is_set_on(struct ring_buffer *buffer);
168	169	void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu);
169	170	void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu);
170	171