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authorSteven Rostedt <srostedt@redhat.com>2008-11-11 15:01:42 -0500
committerSteven Rostedt <srostedt@redhat.com>2008-11-11 15:02:04 -0500
commita358324466b171e145df20bdb74fe81759906de6 (patch)
tree50b2b0b72ff40da6be232eb85d33a203612f3164 /include
parent4143c5cb36331155a1823af8b3a8c761a59fed71 (diff)
downloadop-kernel-dev-a358324466b171e145df20bdb74fe81759906de6.zip
op-kernel-dev-a358324466b171e145df20bdb74fe81759906de6.tar.gz
ring-buffer: buffer record on/off switch
Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Diffstat (limited to 'include')
-rw-r--r--include/linux/ring_buffer.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index 536b0ca..e097c2e 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -120,6 +120,9 @@ unsigned long ring_buffer_overruns(struct ring_buffer *buffer);
u64 ring_buffer_time_stamp(int cpu);
void ring_buffer_normalize_time_stamp(int cpu, u64 *ts);
+void tracing_on(void);
+void tracing_off(void);
+
enum ring_buffer_flags {
RB_FL_OVERWRITE = 1 << 0,
};
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