Re: [PATCH 2/3] [BUGFIX] ring_buffer: tracing: Inherit the tracing setting to next ring buffer
On Mon, 23 Jul 2018 22:25:34 -0400
Steven Rostedt wrote:
> On Sat, 14 Jul 2018 01:28:15 +0900
> Masami Hiramatsu wrote:
>
> > 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.
> >
>
>
> OK, so the issue is that the tracing_on state is saved with the buffer
> itself. And when we swap the buffer, we also swap the state.
>
>
> > Fixes: commit debdd57f5145 ("tracing: Make a snapshot feature available
> > from userspace")
> > Signed-off-by: Masami Hiramatsu
> > Cc: Steven Rostedt
> > Cc: Ingo Molnar
> > Cc: Hiraku Toyooka
> > Cc: sta...@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.
>
> I'd add a little more context here. Something like:
>
> * It may return true when the ring buffer has been disabled by
> * ring_buffer_record_disable(), as that is a temporary disabling of
> * the ring buffer.
Looks nice to me :) It makes the meaning clearer.
Thanks!
>
> -- Steve
>
> > + */
> > +int ring_buffer_record_is_set_on(struct ring_buffer *buffer)
> > +{
> > + return !(atomic_read(>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(>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);
>
--
Masami Hiramatsu
Re: [PATCH 2/3] [BUGFIX] ring_buffer: tracing: Inherit the tracing setting to next ring buffer
On Mon, 23 Jul 2018 22:25:34 -0400
Steven Rostedt wrote:
> On Sat, 14 Jul 2018 01:28:15 +0900
> Masami Hiramatsu wrote:
>
> > 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.
> >
>
>
> OK, so the issue is that the tracing_on state is saved with the buffer
> itself. And when we swap the buffer, we also swap the state.
>
>
> > Fixes: commit debdd57f5145 ("tracing: Make a snapshot feature available
> > from userspace")
> > Signed-off-by: Masami Hiramatsu
> > Cc: Steven Rostedt
> > Cc: Ingo Molnar
> > Cc: Hiraku Toyooka
> > Cc: sta...@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.
>
> I'd add a little more context here. Something like:
>
> * It may return true when the ring buffer has been disabled by
> * ring_buffer_record_disable(), as that is a temporary disabling of
> * the ring buffer.
Looks nice to me :) It makes the meaning clearer.
Thanks!
>
> -- Steve
>
> > + */
> > +int ring_buffer_record_is_set_on(struct ring_buffer *buffer)
> > +{
> > + return !(atomic_read(>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(>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);
>
--
Masami Hiramatsu
Re: [PATCH 2/3] [BUGFIX] ring_buffer: tracing: Inherit the tracing setting to next ring buffer
On Sat, 14 Jul 2018 01:28:15 +0900
Masami Hiramatsu wrote:
> 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.
>
OK, so the issue is that the tracing_on state is saved with the buffer
itself. And when we swap the buffer, we also swap the state.
> Fixes: commit debdd57f5145 ("tracing: Make a snapshot feature available from
> userspace")
> Signed-off-by: Masami Hiramatsu
> Cc: Steven Rostedt
> Cc: Ingo Molnar
> Cc: Hiraku Toyooka
> Cc: sta...@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.
I'd add a little more context here. Something like:
* It may return true when the ring buffer has been disabled by
* ring_buffer_record_disable(), as that is a temporary disabling of
* the ring buffer.
-- Steve
> + */
> +int ring_buffer_record_is_set_on(struct ring_buffer *buffer)
> +{
> + return !(atomic_read(>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(>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);
Re: [PATCH 2/3] [BUGFIX] ring_buffer: tracing: Inherit the tracing setting to next ring buffer
On Sat, 14 Jul 2018 01:28:15 +0900
Masami Hiramatsu wrote:
> 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.
>
OK, so the issue is that the tracing_on state is saved with the buffer
itself. And when we swap the buffer, we also swap the state.
> Fixes: commit debdd57f5145 ("tracing: Make a snapshot feature available from
> userspace")
> Signed-off-by: Masami Hiramatsu
> Cc: Steven Rostedt
> Cc: Ingo Molnar
> Cc: Hiraku Toyooka
> Cc: sta...@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.
I'd add a little more context here. Something like:
* It may return true when the ring buffer has been disabled by
* ring_buffer_record_disable(), as that is a temporary disabling of
* the ring buffer.
-- Steve
> + */
> +int ring_buffer_record_is_set_on(struct ring_buffer *buffer)
> +{
> + return !(atomic_read(>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(>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);
[PATCH 2/3] [BUGFIX] ring_buffer: tracing: Inherit the tracing setting to next ring buffer
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
Cc: Steven Rostedt
Cc: Ingo Molnar
Cc: Hiraku Toyooka
Cc: sta...@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(>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(>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);
[PATCH 2/3] [BUGFIX] ring_buffer: tracing: Inherit the tracing setting to next ring buffer
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
Cc: Steven Rostedt
Cc: Ingo Molnar
Cc: Hiraku Toyooka
Cc: sta...@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(>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(>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);
