FAILED: patch "[PATCH] ring_buffer: tracing: Inherit the tracing setting to next" failed to apply to 4.14-stable tree

PATCH [email protected] 2 participants 3 messages Jul 28, 2018 – Aug 7, 2018

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Stable branch Tracing Tracing ring buffer

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[email protected]

author maintainer

2018-07-28 09:31 UTC #0 lore raw

The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

Quoted 1 line

From 73c8d8945505acdcbae137c2e00a1232e0be709f Mon Sep 17 00:00:00 2001

From: Masami Hiramatsu <[email protected]>
Date: Sat, 14 Jul 2018 01:28:15 +0900
Subject: [PATCH] ring_buffer: tracing: Inherit the tracing setting to next
ring buffer

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 open here

Cc Ingo Molnar <[email protected]>

Cc Shuah Khan <[email protected]>

Cc Tom Zanussi <[email protected]>

Cc Hiraku Toyooka <[email protected]>

Cc [email protected]

Fixes debdd57f5145 ("tracing: Make a snapshot feature available from userspace")

Signed-off-by Masami Hiramatsu <[email protected]>

[ Updated commit log and comment in the code ]

Signed-off-by Steven Rostedt (VMware) <[email protected]>

include/linux/ring_buffer.h +1 -0

index b72ebdff0b77..003d09ab308d 100644
@@ -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);

kernel/trace/ring_buffer.c +16 -0

index 6a46af21765c..0b0b688ea166 100644
@@ -3226,6 +3226,22 @@ int ring_buffer_record_is_on(struct ring_buffer *buffer)
 	return !atomic_read(&buffer->record_disabled);
 }
 
+/**
+ * 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.
+ *
+ * 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.
+ */
+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.

kernel/trace/trace.c +6 -0

index 87cf25171fb8..823687997b01 100644
@@ -1373,6 +1373,12 @@ 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);

Sudip Mukherjee

2018-08-05 23:35 UTC #1 lore raw

Hi Greg,

Quoted 5 lines · On Sat, Jul 28, 2018 at 10:05:45AM +0200, [email protected] wrote:

The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

The attached backported patch should apply to 4.14-stable tree.

--
Regards
Sudip

Quoted 1 line

From 5df8830a89c5494ceea857b3b7cefc19fe24e664 Mon Sep 17 00:00:00 2001

From: Masami Hiramatsu <[email protected]>
Date: Sat, 14 Jul 2018 01:28:15 +0900
Subject: [PATCH] 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.

Link http://lkml.kernel.org/r/153149929558.11274.11730609978254724394.stgit@devbox open here

Cc Ingo Molnar <[email protected]>

Cc Shuah Khan <[email protected]>

Cc Tom Zanussi <[email protected]>

Cc Hiraku Toyooka <[email protected]>

Cc [email protected]

Fixes debdd57f5145 ("tracing: Make a snapshot feature available from userspace")

Signed-off-by Masami Hiramatsu <[email protected]>

[ Updated commit log and comment in the code ]

Signed-off-by Steven Rostedt (VMware) <[email protected]>

Signed-off-by Sudip Mukherjee <[email protected]>

---
 include/linux/ring_buffer.h |  1 +
 kernel/trace/ring_buffer.c  | 16 ++++++++++++++++
 kernel/trace/trace.c        |  6 ++++++
 3 files changed, 23 insertions(+)

include/linux/ring_buffer.h +1 -0

index 289e4d54e3e0..5caa062a02b2 100644
@@ -160,6 +160,7 @@ 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);

kernel/trace/ring_buffer.c +16 -0

index 36f018b15392..fd7809004297 100644
@@ -3110,6 +3110,22 @@ 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.
+ *
+ * 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.
+ */
+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

kernel/trace/trace.c +6 -0

index e268750bd4ad..20919489883f 100644
@@ -1366,6 +1366,12 @@ 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;

Signature · 1 line

2.11.0

Greg KH

author maintainer

2018-08-07 15:33 UTC #2 lore raw

Quoted 10 lines · Sudip Mukherjee

Hi Greg,
Quoted 5 lines · On Sat, Jul 28, 2018 at 10:05:45AM +0200, [email protected] wrote:
The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.
The attached backported patch should apply to 4.14-stable tree.

Applied everywhere, thanks.

greg k-h