tracing: export event trace and trace_marker

PATCH Superseded Tingwei Zhang 3 participants 11 messages Jul 26, 2020 – Jul 28, 2020

Subsystems (4)

Tracing Arm STM32 Hardware tracing facilities System trace module class

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Tingwei Zhang

author

2020-07-26 02:59 UTC #0 lore raw

v2 cover tracing: export event trace and trace_marker

Ftrace has ability to export trace packets to other destionation. Currently, only function trace can be exported. This series extends the support to event trace and trace_maker. STM is one possible destination to export ftrace. Use seperate channel for each CPU to avoid mixing up packets from different CPUs together.

Change from v1:
All changes are suggested by Steven Rostedt.
User seperate flag to control function trace, event trace and trace mark. Allocate channels according to num_possible_cpu() dynamically. Move ftrace_exports routines up so all ftrace can use them.

Tingwei Zhang (6):
stm class: ftrace: change dependency to TRACING
tracing: add flag to control different traces
tracing: add trace_export support for event trace
tracing: add trace_export support for trace_marker stm class: ftrace: enable supported trace export flag stm class: ftrace: use different channel accroding to CPU

 drivers/hwtracing/stm/Kconfig  |   2 +-
 drivers/hwtracing/stm/ftrace.c |   6 +-
 include/linux/trace.h          |   7 +
 kernel/trace/trace.c           | 270 ++++++++++++++++++---------------
 4 files changed, 158 insertions(+), 127 deletions(-)

Signature · 2 lines

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Tingwei Zhang

author

2020-07-26 03:00 UTC #1 lore raw

PATCH v2 1/6 stm class: ftrace: change dependency to TRACING

We will support copying event trace to STM. Change STM_SOURCE_FTRACE to depend on TRACING since we will support multiple tracers.

Signed-off-by Tingwei Zhang <[email protected]>

---
 drivers/hwtracing/stm/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

drivers/hwtracing/stm/Kconfig +1 -1

index d0e92a8a045c..aad594fe79cc 100644
@@ -71,7 +71,7 @@ config STM_SOURCE_HEARTBEAT
 
 config STM_SOURCE_FTRACE
 	tristate "Copy the output from kernel Ftrace to STM engine"
-	depends on FUNCTION_TRACER
+	depends on TRACING
 	help
 	  This option can be used to copy the output from kernel Ftrace
 	  to STM engine. Enabling this option will introduce a slight

Signature · 2 lines

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Tingwei Zhang

author

2020-07-26 03:00 UTC #2 lore raw

PATCH v2 2/6 tracing: add flag to control different traces

In reply to Tingwei Zhang

More traces like event trace or trace marker will be supported. Add flag for difference traces, so that they can be controlled separately. Move current function trace to it's own flag instead of global ftrace enable flag.

Signed-off-by Tingwei Zhang <[email protected]>

---
 include/linux/trace.h |  5 +++++
 kernel/trace/trace.c  | 36 +++++++++++++++++++-----------------
 2 files changed, 24 insertions(+), 17 deletions(-)

include/linux/trace.h +5 -0

index 7fd86d3c691f..d2fdf9be84b5 100644
@@ -3,6 +3,9 @@
 #define _LINUX_TRACE_H
 
 #ifdef CONFIG_TRACING
+
+#define TRACE_EXPORT_FUNCTION	BIT_ULL(0)
+
 /*
  * The trace export - an export of Ftrace output. The trace_export
  * can process traces and export them to a registered destination as

@@ -15,10 +18,12 @@
  * next		- pointer to the next trace_export
  * write	- copy traces which have been delt with ->commit() to
  *		  the destination
+ * flags	- which ftrace to be exported
  */
 struct trace_export {
 	struct trace_export __rcu	*next;
 	void (*write)(struct trace_export *, const void *, unsigned int);
+	int flags;
 };
 
 int register_ftrace_export(struct trace_export *export);

kernel/trace/trace.c +19 ~~-17~~

index bb62269724d5..8f1e66831e9e 100644
@@ -2747,33 +2747,37 @@ trace_buffer_unlock_commit_nostack(struct trace_buffer *buffer,
 
 static void
 trace_process_export(struct trace_export *export,
-	       struct ring_buffer_event *event)
+	       struct ring_buffer_event *event, int flag)
 {
 	struct trace_entry *entry;
 	unsigned int size = 0;
 
-	entry = ring_buffer_event_data(event);
-	size = ring_buffer_event_length(event);
-	export->write(export, entry, size);
+	if (export->flags & flag) {
+		entry = ring_buffer_event_data(event);
+		size = ring_buffer_event_length(event);
+		export->write(export, entry, size);
+	}
 }
 
 static DEFINE_MUTEX(ftrace_export_lock);
 
 static struct trace_export __rcu *ftrace_exports_list __read_mostly;
 
-static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled);
+static DEFINE_STATIC_KEY_FALSE(trace_function_exports_enabled);
 
-static inline void ftrace_exports_enable(void)
+static inline void ftrace_exports_enable(struct trace_export *export)
 {
-	static_branch_enable(&ftrace_exports_enabled);
+	if (export->flags & TRACE_EXPORT_FUNCTION)
+		static_branch_inc(&trace_function_exports_enabled);
 }
 
-static inline void ftrace_exports_disable(void)
+static inline void ftrace_exports_disable(struct trace_export *export)
 {
-	static_branch_disable(&ftrace_exports_enabled);
+	if (export->flags & TRACE_EXPORT_FUNCTION)
+		static_branch_dec(&trace_function_exports_enabled);
 }
 
-static void ftrace_exports(struct ring_buffer_event *event)
+static void ftrace_exports(struct ring_buffer_event *event, int flag)
 {
 	struct trace_export *export;

@@ -2781,7 +2785,7 @@ static void ftrace_exports(struct ring_buffer_event *event)
 
 	export = rcu_dereference_raw_check(ftrace_exports_list);
 	while (export) {
-		trace_process_export(export, event);
+		trace_process_export(export, event, flag);
 		export = rcu_dereference_raw_check(export->next);
 	}

@@ -2821,8 +2825,7 @@ rm_trace_export(struct trace_export **list, struct trace_export *export)
 static inline void
 add_ftrace_export(struct trace_export **list, struct trace_export *export)
 {
-	if (*list == NULL)
-		ftrace_exports_enable();
+	ftrace_exports_enable(export);
 
 	add_trace_export(list, export);
 }

@@ -2833,8 +2836,7 @@ rm_ftrace_export(struct trace_export **list, struct trace_export *export)
 	int ret;
 
 	ret = rm_trace_export(list, export);
-	if (*list == NULL)
-		ftrace_exports_disable();
+	ftrace_exports_disable(export);
 
 	return ret;
 }

@@ -2887,8 +2889,8 @@ trace_function(struct trace_array *tr,
 	entry->parent_ip		= parent_ip;
 
 	if (!call_filter_check_discard(call, entry, buffer, event)) {
-		if (static_branch_unlikely(&ftrace_exports_enabled))
-			ftrace_exports(event);
+		if (static_branch_unlikely(&trace_function_exports_enabled))
+			ftrace_exports(event, TRACE_EXPORT_FUNCTION);
 		__buffer_unlock_commit(buffer, event);
 	}
 }

Signature · 2 lines

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Steven Rostedt

maintainer

2020-07-27 18:46 UTC #3 lore raw

Re: [PATCH v2 2/6] tracing: add flag to control different traces

include/linux/trace.h line 7

Quoted 10 lines · On Sun, 26 Jul 2020 10:59:27 +0800 Tingwei Zhang <[email protected]> wrote:

include/linux/trace.h +2 -0

index 7fd86d3c691f..d2fdf9be84b5 100644
@@ -3,6 +3,9 @@
 #define _LINUX_TRACE_H
 
 #ifdef CONFIG_TRACING
+
+#define TRACE_EXPORT_FUNCTION	BIT_ULL(0)

All the flags variables below are defined as "int". Why the BIT_ULL()? BIT(0) should work just fine. The ULL makes one think these flags will be used for unsigned long variables, which it is not.

-- Steve

Quoted 32 lines

include/linux/trace.h +1 -0

+
 
 struct trace_export {
 	struct trace_export __rcu	*next;

include/linux/trace.h +1 -0

 	void (*write)(struct trace_export *, const void *, unsigned int);
+	int flags;
 };
 
 int register_ftrace_export(struct trace_export *export);

kernel/trace/trace.c +6 -4

index bb62269724d5..8f1e66831e9e 100644
@@ -2747,33 +2747,37 @@ trace_buffer_unlock_commit_nostack(struct trace_buffer *buffer,
 
 static void
 trace_process_export(struct trace_export *export,
-	       struct ring_buffer_event *event)
+	       struct ring_buffer_event *event, int flag)
 {
 	struct trace_entry *entry;
 	unsigned int size = 0;
 
-	entry = ring_buffer_event_data(event);
-	size = ring_buffer_event_length(event);
-	export->write(export, entry, size);
+	if (export->flags & flag) {
+		entry = ring_buffer_event_data(event);
+		size = ring_buffer_event_length(event);
+		export->write(export, entry, size);
+	}
 }

Tingwei Zhang

2020-07-28 00:29 UTC #4 lore raw

Re: [PATCH v2 2/6] tracing: add flag to control different traces

Hi Steve,

Quoted 11 lines · Steven Rostedt

Quoted 7 lines · On Sun, 26 Jul 2020 10:59:27 +0800 Tingwei Zhang <[email protected]> wrote:
include/linux/trace.h +0 -0
index 7fd86d3c691f..d2fdf9be84b5 100644
@@ -3,6 +3,9 @@
 #define _LINUX_TRACE_H
 

Quoted 8 lines

include/linux/trace.h line 7
Quoted 3 lines
include/linux/trace.h +2 -0
 #ifdef CONFIG_TRACING
+
+#define TRACE_EXPORT_FUNCTION	BIT_ULL(0)
All the flags variables below are defined as "int". Why the BIT_ULL()? BIT(0) should work just fine. The ULL makes one think these flags will be used for unsigned long variables, which it is not.

That's my mistake. Thanks for point that out. I'll fix it in next revision.

Quoted 36 lines

-- Steve

kernel/trace/trace.c trace_buffer_unlock_commit_nostack(struct

Quoted 14 lines

include/linux/trace.h +1 -0

+
 
 struct trace_export {
 	struct trace_export __rcu	*next;

include/linux/trace.h +1 -0

 	void (*write)(struct trace_export *, const void *, unsigned int);
+	int flags;
 };
 
 int register_ftrace_export(struct trace_export *export);

kernel/trace/trace.c +0 -0

index bb62269724d5..8f1e66831e9e 100644
@@ -2747,33 +2747,37 @@ trace_buffer_unlock_commit_nostack(struct

trace_buffer *buffer,

Quoted 18 lines

kernel/trace/trace.c +6 -4

 static void
 trace_process_export(struct trace_export *export,
-	       struct ring_buffer_event *event)
+	       struct ring_buffer_event *event, int flag)
 {
 	struct trace_entry *entry;
 	unsigned int size = 0;
 
-	entry = ring_buffer_event_data(event);
-	size = ring_buffer_event_length(event);
-	export->write(export, entry, size);
+	if (export->flags & flag) {
+		entry = ring_buffer_event_data(event);
+		size = ring_buffer_event_length(event);
+		export->write(export, entry, size);
+	}
 }

Tingwei Zhang

author

2020-07-26 03:00 UTC #5 lore raw

PATCH v2 3/6 tracing: add trace_export support for event trace

In reply to Tingwei Zhang

Only function traces can be exported to other destinations currently. This patch exports event trace as well. Move trace export related function to the beginning of file so other trace can call trace_process_export() to export.

Signed-off-by Tingwei Zhang <[email protected]>

---
 include/linux/trace.h |   1 +
 kernel/trace/trace.c  | 259 ++++++++++++++++++++++--------------------
 2 files changed, 135 insertions(+), 125 deletions(-)

include/linux/trace.h +1 -0

index d2fdf9be84b5..91f6f1c0f2db 100644
@@ -5,6 +5,7 @@
 #ifdef CONFIG_TRACING
 
 #define TRACE_EXPORT_FUNCTION	BIT_ULL(0)
+#define TRACE_EXPORT_EVENT	BIT_ULL(1)
 
 /*
  * The trace export - an export of Ftrace output. The trace_export

kernel/trace/trace.c +134 ~~-125~~

277 lines not on this page · raw message

Signature · 2 lines

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Tingwei Zhang

author

2020-07-26 03:00 UTC #6 lore raw

PATCH v2 4/6 tracing: add trace_export support for trace_marker

In reply to Tingwei Zhang

Add the support to route trace_marker buffer to other destination via trace_export.

Signed-off-by Tingwei Zhang <[email protected]>

---
 include/linux/trace.h | 1 +
 kernel/trace/trace.c  | 9 +++++++++
 2 files changed, 10 insertions(+)

include/linux/trace.h +1 -0

index 91f6f1c0f2db..4bb6918fbf44 100644
@@ -6,6 +6,7 @@
 
 #define TRACE_EXPORT_FUNCTION	BIT_ULL(0)
 #define TRACE_EXPORT_EVENT	BIT_ULL(1)
+#define TRACE_EXPORT_MARKER	BIT_ULL(2)
 
 /*
  * The trace export - an export of Ftrace output. The trace_export

kernel/trace/trace.c +9 -0

index 2f9302a8b322..67993abda394 100644
@@ -271,6 +271,7 @@ static struct trace_export __rcu *ftrace_exports_list __read_mostly;
 
 static DEFINE_STATIC_KEY_FALSE(trace_function_exports_enabled);
 static DEFINE_STATIC_KEY_FALSE(trace_event_exports_enabled);
+static DEFINE_STATIC_KEY_FALSE(trace_marker_exports_enabled);
 
 static inline void ftrace_exports_enable(struct trace_export *export)
 {

@@ -279,6 +280,9 @@ static inline void ftrace_exports_enable(struct trace_export *export)
 
 	if (export->flags & TRACE_EXPORT_EVENT)
 		static_branch_inc(&trace_event_exports_enabled);
+
+	if (export->flags & TRACE_EXPORT_MARKER)
+		static_branch_inc(&trace_marker_exports_enabled);
 }
 
 static inline void ftrace_exports_disable(struct trace_export *export)

@@ -288,6 +292,9 @@ static inline void ftrace_exports_disable(struct trace_export *export)
 
 	if (export->flags & TRACE_EXPORT_EVENT)
 		static_branch_dec(&trace_event_exports_enabled);
+
+	if (export->flags & TRACE_EXPORT_MARKER)
+		static_branch_dec(&trace_marker_exports_enabled);
 }
 
 static void ftrace_exports(struct ring_buffer_event *event, int flag)

@@ -6648,6 +6655,8 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
 	} else
 		entry->buf[cnt] = '\0';
 
+	if (static_branch_unlikely(&trace_marker_exports_enabled))
+		ftrace_exports(event, TRACE_EXPORT_MARKER);
 	__buffer_unlock_commit(buffer, event);
 
 	if (tt)

Signature · 2 lines

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Tingwei Zhang

author

2020-07-26 03:00 UTC #7 lore raw

PATCH v2 5/6 stm class: ftrace: enable supported trace export flag

In reply to Tingwei Zhang

Set flags for trace_export. Export function trace, event trace and trace marker to stm.

Signed-off-by Tingwei Zhang <[email protected]>

---
 drivers/hwtracing/stm/ftrace.c | 2 ++
 1 file changed, 2 insertions(+)

drivers/hwtracing/stm/ftrace.c +2 -0

index ce868e095410..c694a6e692d1 100644
@@ -46,6 +46,8 @@ static int stm_ftrace_link(struct stm_source_data *data)
 	struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
 
 	sf->ftrace.write = stm_ftrace_write;
+	sf->ftrace.flags = TRACE_EXPORT_FUNCTION | TRACE_EXPORT_EVENT
+			| TRACE_EXPORT_MARKER;
 
 	return register_ftrace_export(&sf->ftrace);
 }

Signature · 2 lines

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Tingwei Zhang

author

2020-07-26 03:00 UTC #8 lore raw

PATCH v2 6/6 stm class: ftrace: use different channel accroding to CPU

In reply to Tingwei Zhang

To avoid mixup of packets from differnt ftrace packets simultaneously, use different channel for packets from different CPU.

Signed-off-by Tingwei Zhang <[email protected]>

---
 drivers/hwtracing/stm/ftrace.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

drivers/hwtracing/stm/ftrace.c +3 -1

index c694a6e692d1..9893a0e8eced 100644
@@ -37,8 +37,9 @@ static void notrace
 stm_ftrace_write(struct trace_export *export, const void *buf, unsigned int len)
 {
 	struct stm_ftrace *stm = container_of(export, struct stm_ftrace, ftrace);
+	unsigned int cpu = smp_processor_id();
 
-	stm_source_write(&stm->data, STM_FTRACE_CHAN, buf, len);
+	stm_source_write(&stm->data, STM_FTRACE_CHAN + cpu, buf, len);
 }
 
 static int stm_ftrace_link(struct stm_source_data *data)

@@ -63,6 +64,7 @@ static int __init stm_ftrace_init(void)
 {
 	int ret;
 
+	stm_ftrace.data.nr_chans = num_possible_cpus();
 	ret = stm_source_register_device(NULL, &stm_ftrace.data);
 	if (ret)
 		pr_err("Failed to register stm_source - ftrace.\n");

Signature · 2 lines

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Steven Rostedt

maintainer Reviewed-by on v2 6/6

2020-07-27 19:08 UTC #9 lore raw

Re: [PATCH v2 6/6] stm class: ftrace: use different channel accroding to CPU

drivers/hwtracing/stm/ftrace.c static void notrace · line 40

Quoted 7 lines · On Sun, 26 Jul 2020 10:59:31 +0800 Tingwei Zhang <[email protected]> wrote:

drivers/hwtracing/stm/ftrace.c +1 -0

@@ -37,8 +37,9 @@ static void notrace
 stm_ftrace_write(struct trace_export *export, const void *buf, unsigned int len)
 {
 	struct stm_ftrace *stm = container_of(export, struct stm_ftrace, ftrace);
+	unsigned int cpu = smp_processor_id();

Probably should add a comment to the above stating that this is called from the tracing system with preemption disabled.

Other than my two comments:

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

-- Steve

Quoted 6 lines

drivers/hwtracing/stm/ftrace.c +1 -1

-	stm_source_write(&stm->data, STM_FTRACE_CHAN, buf, len);
+	stm_source_write(&stm->data, STM_FTRACE_CHAN + cpu, buf, len);
 }
 
 static int stm_ftrace_link(struct stm_source_data *data)

Tingwei Zhang

2020-07-28 00:28 UTC #10 lore raw

Re: [PATCH v2 6/6] stm class: ftrace: use different channel accroding to CPU

Hi Steve,

Quoted 8 lines · Steven Rostedt

drivers/hwtracing/stm/ftrace.c static void notrace · line 37
Quoted 4 lines · On Sun, 26 Jul 2020 10:59:31 +0800 Tingwei Zhang <[email protected]> wrote:
drivers/hwtracing/stm/ftrace.c +0 -0
@@ -37,8 +37,9 @@ static void notrace
 stm_ftrace_write(struct trace_export *export, const void *buf, unsigned
int len)

Quoted 8 lines

drivers/hwtracing/stm/ftrace.c static void notrace · line 39
Quoted 2 lines
drivers/hwtracing/stm/ftrace.c +0 -0
 {
 	struct stm_ftrace *stm = container_of(export, struct stm_ftrace,
ftrace);
drivers/hwtracing/stm/ftrace.c static void notrace · line 40
Quoted 1 line
drivers/hwtracing/stm/ftrace.c +1 -0
+	unsigned int cpu = smp_processor_id();
Probably should add a comment to the above stating that this is called from the tracing system with preemption disabled.

Good point. I'll add that comment in next revision.

Thanks,
Tingwei

Quoted 13 lines

Other than my two comments:
Reviewed-by Steven Rostedt (VMware) <[email protected]>
-- Steve
Quoted 6 lines
drivers/hwtracing/stm/ftrace.c +1 -1
-	stm_source_write(&stm->data, STM_FTRACE_CHAN, buf, len);
+	stm_source_write(&stm->data, STM_FTRACE_CHAN + cpu, buf, len);
 }
 
 static int stm_ftrace_link(struct stm_source_data *data)