diff options
| author | Masami Hiramatsu <mhiramat@kernel.org> | 2018-07-14 01:28:15 +0900 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-08-09 12:19:28 +0200 |
| commit | 731ccd90b8dc6697fefb62f43ed6f8d253d7fd5b (patch) | |
| tree | 47c4b2772ca8698d458e684008c52a6e49387999 /kernel/trace/trace.c | |
| parent | fef9866d278ee726b15cf251339660e77ba5488c (diff) | |
ring_buffer: tracing: Inherit the tracing setting to next ring buffer
commit 73c8d8945505acdcbae137c2e00a1232e0be709f upstream.
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
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: Hiraku Toyooka <hiraku.toyooka@cybertrust.co.jp>
Cc: stable@vger.kernel.org
Fixes: debdd57f5145 ("tracing: Make a snapshot feature available from userspace")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
[ Updated commit log and comment in the code ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/trace/trace.c')
| -rw-r--r-- | kernel/trace/trace.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 8aef4e63ac57..1b980a8ef791 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1088,6 +1088,12 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu) arch_spin_lock(&tr->max_lock); + /* Inherit the recordable setting from trace_buffer */ + if (ring_buffer_record_is_set_on(tr->trace_buffer.buffer)) + ring_buffer_record_on(tr->max_buffer.buffer); + else + ring_buffer_record_off(tr->max_buffer.buffer); + buf = tr->trace_buffer.buffer; tr->trace_buffer.buffer = tr->max_buffer.buffer; tr->max_buffer.buffer = buf; |