From: Masami Hiramatsu <mhiramat@kernel.org> To: Steven Rostedt <rostedt@goodmis.org> Cc: Ingo Molnar <mingo@redhat.com>, Shuah Khan <shuah@kernel.org>, Masami Hiramatsu <mhiramat@kernel.org>, Tom Zanussi <tom.zanussi@linux.intel.com>, Hiraku Toyooka <hiraku.toyooka@cybertrust.co.jp>, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH 2/3] [BUGFIX] ring_buffer: tracing: Inherit the tracing setting to next ring buffer Date: Sat, 14 Jul 2018 01:28:15 +0900 Message-ID: <153149929558.11274.11730609978254724394.stgit@devbox> (raw) In-Reply-To: <153149923649.11274.14970833360963898112.stgit@devbox> Inherit the tracing on/off setting on ring_buffer to next trace buffer when taking a snapshot. Taking a snapshot is done by swapping with backup ring buffer (max_tr_buffer). But since the tracing on/off setting is set in the ring buffer, when swapping it, 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 # 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 must be a bug, because user never know that each "ring_buffer" stores tracing-enable state and snapshot is done by swapping ring buffers. This patch fixes above strange behavior. Fixes: commit debdd57f5145 ("tracing: Make a snapshot feature available from userspace") Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Hiraku Toyooka <hiraku.toyooka@cybertrust.co.jp> Cc: stable@vger.kernel.org --- include/linux/ring_buffer.h | 1 + kernel/trace/ring_buffer.c | 12 ++++++++++++ kernel/trace/trace.c | 6 ++++++ 3 files changed, 19 insertions(+) diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index b72ebdff0b77..003d09ab308d 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -165,6 +165,7 @@ void ring_buffer_record_enable(struct ring_buffer *buffer); void ring_buffer_record_off(struct ring_buffer *buffer); void ring_buffer_record_on(struct ring_buffer *buffer); int ring_buffer_record_is_on(struct ring_buffer *buffer); +int ring_buffer_record_is_set_on(struct ring_buffer *buffer); void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu); void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu); diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 6a46af21765c..4038ed74ab95 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -3227,6 +3227,18 @@ int ring_buffer_record_is_on(struct ring_buffer *buffer) } /** + * ring_buffer_record_is_set_on - return true if the ring buffer is set writable + * @buffer: The ring buffer to see if write is set enabled + * + * Returns true if the ring buffer is set writable by ring_buffer_record_on(). + * Note that this does NOT mean it is in a writable state. + */ +int ring_buffer_record_is_set_on(struct ring_buffer *buffer) +{ + return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF); +} + +/** * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer * @buffer: The ring buffer to stop writes to. * @cpu: The CPU buffer to stop diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 2556d8c097d2..bbd5a94a7ef1 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1378,6 +1378,12 @@ 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); + swap(tr->trace_buffer.buffer, tr->max_buffer.buffer); __update_max_tr(tr, tsk, cpu);
next prev parent reply index Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-07-13 16:27 [PATCH 0/3] tracing: Fix bugs on snapshot feature Masami Hiramatsu 2018-07-13 16:27 ` [PATCH 1/3] [BUGFIX] tracing: Fix double free of event_trigger_data Masami Hiramatsu 2018-07-24 2:10 ` Steven Rostedt 2018-07-24 15:09 ` Masami Hiramatsu 2018-07-24 20:49 ` Steven Rostedt 2018-07-24 21:30 ` Steven Rostedt 2018-07-24 23:13 ` Steven Rostedt 2018-07-25 1:16 ` Masami Hiramatsu 2018-07-25 2:41 ` Steven Rostedt 2018-07-25 14:14 ` Masami Hiramatsu 2018-07-25 16:01 ` Tom Zanussi 2018-07-25 16:09 ` Steven Rostedt 2018-07-25 1:05 ` Masami Hiramatsu 2018-07-13 16:28 ` Masami Hiramatsu [this message] 2018-07-24 2:25 ` [PATCH 2/3] [BUGFIX] ring_buffer: tracing: Inherit the tracing setting to next ring buffer Steven Rostedt 2018-07-24 14:30 ` Masami Hiramatsu 2018-07-13 16:28 ` [PATCH 3/3] selftests/ftrace: Add snapshot and tracing_on test case Masami Hiramatsu
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