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| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2020-03-17 17:32:31 -0400 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2020-03-27 16:39:01 -0400 |
| commit | 06e0a548bad0f43a21e036db018e4dadb501ce8b (patch) | |
| tree | 7587fb20e56bbb7fecf55fb4c9f0c6729b55f67d | |
| parent | 1039221cc2787dee51a7ffbf9b0e79d192dadf76 (diff) | |
| download | lwn-06e0a548bad0f43a21e036db018e4dadb501ce8b.tar.gz lwn-06e0a548bad0f43a21e036db018e4dadb501ce8b.zip | |
tracing: Do not disable tracing when reading the trace file
When opening the "trace" file, it is no longer necessary to disable tracing.
Note, a new option is created called "pause-on-trace", when set, will cause
the trace file to emulate its original behavior.
Link: http://lkml.kernel.org/r/20200317213416.903351225@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
| -rw-r--r-- | Documentation/trace/ftrace.rst | 6 | ||||
| -rw-r--r-- | kernel/trace/trace.c | 9 | ||||
| -rw-r--r-- | kernel/trace/trace.h | 1 |
3 files changed, 13 insertions, 3 deletions
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 99a0890e20ec..c33950a35d65 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -1125,6 +1125,12 @@ Here are the available options: the trace displays additional information about the latency, as described in "Latency trace format". + pause-on-trace + When set, opening the trace file for read, will pause + writing to the ring buffer (as if tracing_on was set to zero). + This simulates the original behavior of the trace file. + When the file is closed, tracing will be enabled again. + record-cmd When any event or tracer is enabled, a hook is enabled in the sched_switch trace point to fill comm cache diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 47889123be7f..650fa81fffe8 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4273,8 +4273,11 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot) if (trace_clocks[tr->clock_id].in_ns) iter->iter_flags |= TRACE_FILE_TIME_IN_NS; - /* stop the trace while dumping if we are not opening "snapshot" */ - if (!iter->snapshot) + /* + * If pause-on-trace is enabled, then stop the trace while + * dumping, unless this is the "snapshot" file + */ + if (!iter->snapshot && (tr->trace_flags & TRACE_ITER_PAUSE_ON_TRACE)) tracing_stop_tr(tr); if (iter->cpu_file == RING_BUFFER_ALL_CPUS) { @@ -4371,7 +4374,7 @@ static int tracing_release(struct inode *inode, struct file *file) if (iter->trace && iter->trace->close) iter->trace->close(iter); - if (!iter->snapshot) + if (!iter->snapshot && tr->stop_count) /* reenable tracing if it was previously enabled */ tracing_start_tr(tr); diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index c61e1b1c85a6..f37e05135986 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1302,6 +1302,7 @@ extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf, C(IRQ_INFO, "irq-info"), \ C(MARKERS, "markers"), \ C(EVENT_FORK, "event-fork"), \ + C(PAUSE_ON_TRACE, "pause-on-trace"), \ FUNCTION_FLAGS \ FGRAPH_FLAGS \ STACK_FLAGS \ |