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| author | Steven Rostedt (Red Hat) <rostedt@goodmis.org> | 2013-03-12 13:26:18 -0400 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2013-03-15 00:36:03 -0400 |
| commit | 417944c4c7a0f657158d0515f3b8e8c043fd788f (patch) | |
| tree | 838e9bb09f8df63af3adf5b865d3781eeac8d6ba /include/trace | |
| parent | 7818b3886545f89549185e4023743e2df91d1fa1 (diff) | |
| download | lwn-417944c4c7a0f657158d0515f3b8e8c043fd788f.tar.gz lwn-417944c4c7a0f657158d0515f3b8e8c043fd788f.zip | |
tracing: Add a way to soft disable trace events
In order to let triggers enable or disable events, we need a 'soft'
method for doing so. For example, if a function probe is added that
lets a user enable or disable events when a function is called, that
change must be done without taking locks or a mutex, and definitely
it can't sleep. But the full enabling of a tracepoint is expensive.
By adding a 'SOFT_DISABLE' flag, and converting the flags to be updated
without the protection of a mutex (using set/clear_bit()), this soft
disable flag can be used to allow critical sections to enable or disable
events from being traced (after the event has been placed into "SOFT_MODE").
Some caveats though: The comm recorder (to map pids with a comm) can not
be soft disabled (yet). If you disable an event with with a "soft"
disable and wait a while before reading the trace, the comm cache may be
replaced and you'll get a bunch of <...> for comms in the trace.
Reading the "enable" file for an event that is disabled will now give
you "0*" where the '*' denotes that the tracepoint is still active but
the event itself is "disabled".
[ fixed _BIT used in & operation : thanks to Dan Carpenter and smatch ]
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'include/trace')
| -rw-r--r-- | include/trace/ftrace.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h index bbf09c2021b9..4bda044e6c77 100644 --- a/include/trace/ftrace.h +++ b/include/trace/ftrace.h @@ -413,6 +413,10 @@ static inline notrace int ftrace_get_offsets_##call( \ * int __data_size; * int pc; * + * if (test_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, + * &ftrace_file->flags)) + * return; + * * local_save_flags(irq_flags); * pc = preempt_count(); * @@ -518,6 +522,10 @@ ftrace_raw_event_##call(void *__data, proto) \ int __data_size; \ int pc; \ \ + if (test_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, \ + &ftrace_file->flags)) \ + return; \ + \ local_save_flags(irq_flags); \ pc = preempt_count(); \ \ |