[PATCH v3 0/6] tracing: export event trace and trace_marker

[PATCH v3 0/6] tracing: export event trace and trace_marker

[Tingwei Zhang]

Ftrace has ability to export trace packets to other destination.
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 separate channel for each CPU to avoid mixing up packets
from different CPUs together.

Change from v2:
Change flag definition to BIT(). (Steven)
Add comment in stm_ftrace_write() to clarify it's safe to use 
smp_processor_id() here since preempt is disabled. (Steven) 

Change from v1:
All changes are suggested by Steven Rostedt.
User separate 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 |   7 +-
 include/linux/trace.h          |   7 +
 kernel/trace/trace.c           | 270 ++++++++++++++++++---------------
 4 files changed, 159 insertions(+), 127 deletions(-)

-- 
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[PATCH v3 1/6] stm class: ftrace: change dependency to TRACING

[Tingwei Zhang]

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 <tingwei@codeaurora.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 drivers/hwtracing/stm/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwtracing/stm/Kconfig b/drivers/hwtracing/stm/Kconfig
index d0e92a8a045c..aad594fe79cc 100644
--- a/drivers/hwtracing/stm/Kconfig
+++ b/drivers/hwtracing/stm/Kconfig
@@ -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
-- 
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[PATCH v3 2/6] tracing: add flag to control different traces

[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 <tingwei@codeaurora.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/linux/trace.h |  5 +++++
 kernel/trace/trace.c  | 36 +++++++++++++++++++-----------------
 2 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/include/linux/trace.h b/include/linux/trace.h
index 7fd86d3c691f..bc93063dda39 100644
--- a/include/linux/trace.h
+++ b/include/linux/trace.h
@@ -3,6 +3,9 @@
 #define _LINUX_TRACE_H
 
 #ifdef CONFIG_TRACING
+
+#define TRACE_EXPORT_FUNCTION	BIT(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);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index bb62269724d5..8f1e66831e9e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -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);
 	}
 }
-- 
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[PATCH v3 3/6] tracing: add trace_export support for event trace

[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 <tingwei@codeaurora.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/linux/trace.h |   1 +
 kernel/trace/trace.c  | 259 ++++++++++++++++++++++--------------------
 2 files changed, 135 insertions(+), 125 deletions(-)

diff --git a/include/linux/trace.h b/include/linux/trace.h
index bc93063dda39..5a01eeffb254 100644
--- a/include/linux/trace.h
+++ b/include/linux/trace.h
@@ -5,6 +5,7 @@
 #ifdef CONFIG_TRACING
 
 #define TRACE_EXPORT_FUNCTION	BIT(0)
+#define TRACE_EXPORT_EVENT	BIT(1)
 
 /*
  * The trace export - an export of Ftrace output. The trace_export
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8f1e66831e9e..2f9302a8b322 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -251,6 +251,138 @@ unsigned long long ns2usecs(u64 nsec)
 	return nsec;
 }
 
+static void
+trace_process_export(struct trace_export *export,
+	       struct ring_buffer_event *event, int flag)
+{
+	struct trace_entry *entry;
+	unsigned int size = 0;
+
+	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(trace_function_exports_enabled);
+static DEFINE_STATIC_KEY_FALSE(trace_event_exports_enabled);
+
+static inline void ftrace_exports_enable(struct trace_export *export)
+{
+	if (export->flags & TRACE_EXPORT_FUNCTION)
+		static_branch_inc(&trace_function_exports_enabled);
+
+	if (export->flags & TRACE_EXPORT_EVENT)
+		static_branch_inc(&trace_event_exports_enabled);
+}
+
+static inline void ftrace_exports_disable(struct trace_export *export)
+{
+	if (export->flags & TRACE_EXPORT_FUNCTION)
+		static_branch_dec(&trace_function_exports_enabled);
+
+	if (export->flags & TRACE_EXPORT_EVENT)
+		static_branch_dec(&trace_event_exports_enabled);
+}
+
+static void ftrace_exports(struct ring_buffer_event *event, int flag)
+{
+	struct trace_export *export;
+
+	preempt_disable_notrace();
+
+	export = rcu_dereference_raw_check(ftrace_exports_list);
+	while (export) {
+		trace_process_export(export, event, flag);
+		export = rcu_dereference_raw_check(export->next);
+	}
+
+	preempt_enable_notrace();
+}
+
+static inline void
+add_trace_export(struct trace_export **list, struct trace_export *export)
+{
+	rcu_assign_pointer(export->next, *list);
+	/*
+	 * We are entering export into the list but another
+	 * CPU might be walking that list. We need to make sure
+	 * the export->next pointer is valid before another CPU sees
+	 * the export pointer included into the list.
+	 */
+	rcu_assign_pointer(*list, export);
+}
+
+static inline int
+rm_trace_export(struct trace_export **list, struct trace_export *export)
+{
+	struct trace_export **p;
+
+	for (p = list; *p != NULL; p = &(*p)->next)
+		if (*p == export)
+			break;
+
+	if (*p != export)
+		return -1;
+
+	rcu_assign_pointer(*p, (*p)->next);
+
+	return 0;
+}
+
+static inline void
+add_ftrace_export(struct trace_export **list, struct trace_export *export)
+{
+	ftrace_exports_enable(export);
+
+	add_trace_export(list, export);
+}
+
+static inline int
+rm_ftrace_export(struct trace_export **list, struct trace_export *export)
+{
+	int ret;
+
+	ret = rm_trace_export(list, export);
+	ftrace_exports_disable(export);
+
+	return ret;
+}
+
+int register_ftrace_export(struct trace_export *export)
+{
+	if (WARN_ON_ONCE(!export->write))
+		return -1;
+
+	mutex_lock(&ftrace_export_lock);
+
+	add_ftrace_export(&ftrace_exports_list, export);
+
+	mutex_unlock(&ftrace_export_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(register_ftrace_export);
+
+int unregister_ftrace_export(struct trace_export *export)
+{
+	int ret;
+
+	mutex_lock(&ftrace_export_lock);
+
+	ret = rm_ftrace_export(&ftrace_exports_list, export);
+
+	mutex_unlock(&ftrace_export_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(unregister_ftrace_export);
+
 /* trace_flags holds trace_options default values */
 #define TRACE_DEFAULT_FLAGS						\
 	(FUNCTION_DEFAULT_FLAGS |					\
@@ -2702,6 +2834,8 @@ void trace_event_buffer_commit(struct trace_event_buffer *fbuffer)
 	if (static_key_false(&tracepoint_printk_key.key))
 		output_printk(fbuffer);
 
+	if (static_branch_unlikely(&trace_event_exports_enabled))
+		ftrace_exports(fbuffer->event, TRACE_EXPORT_EVENT);
 	event_trigger_unlock_commit_regs(fbuffer->trace_file, fbuffer->buffer,
 				    fbuffer->event, fbuffer->entry,
 				    fbuffer->flags, fbuffer->pc, fbuffer->regs);
@@ -2745,131 +2879,6 @@ trace_buffer_unlock_commit_nostack(struct trace_buffer *buffer,
 	__buffer_unlock_commit(buffer, event);
 }
 
-static void
-trace_process_export(struct trace_export *export,
-	       struct ring_buffer_event *event, int flag)
-{
-	struct trace_entry *entry;
-	unsigned int size = 0;
-
-	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(trace_function_exports_enabled);
-
-static inline void ftrace_exports_enable(struct trace_export *export)
-{
-	if (export->flags & TRACE_EXPORT_FUNCTION)
-		static_branch_inc(&trace_function_exports_enabled);
-}
-
-static inline void ftrace_exports_disable(struct trace_export *export)
-{
-	if (export->flags & TRACE_EXPORT_FUNCTION)
-		static_branch_dec(&trace_function_exports_enabled);
-}
-
-static void ftrace_exports(struct ring_buffer_event *event, int flag)
-{
-	struct trace_export *export;
-
-	preempt_disable_notrace();
-
-	export = rcu_dereference_raw_check(ftrace_exports_list);
-	while (export) {
-		trace_process_export(export, event, flag);
-		export = rcu_dereference_raw_check(export->next);
-	}
-
-	preempt_enable_notrace();
-}
-
-static inline void
-add_trace_export(struct trace_export **list, struct trace_export *export)
-{
-	rcu_assign_pointer(export->next, *list);
-	/*
-	 * We are entering export into the list but another
-	 * CPU might be walking that list. We need to make sure
-	 * the export->next pointer is valid before another CPU sees
-	 * the export pointer included into the list.
-	 */
-	rcu_assign_pointer(*list, export);
-}
-
-static inline int
-rm_trace_export(struct trace_export **list, struct trace_export *export)
-{
-	struct trace_export **p;
-
-	for (p = list; *p != NULL; p = &(*p)->next)
-		if (*p == export)
-			break;
-
-	if (*p != export)
-		return -1;
-
-	rcu_assign_pointer(*p, (*p)->next);
-
-	return 0;
-}
-
-static inline void
-add_ftrace_export(struct trace_export **list, struct trace_export *export)
-{
-	ftrace_exports_enable(export);
-
-	add_trace_export(list, export);
-}
-
-static inline int
-rm_ftrace_export(struct trace_export **list, struct trace_export *export)
-{
-	int ret;
-
-	ret = rm_trace_export(list, export);
-	ftrace_exports_disable(export);
-
-	return ret;
-}
-
-int register_ftrace_export(struct trace_export *export)
-{
-	if (WARN_ON_ONCE(!export->write))
-		return -1;
-
-	mutex_lock(&ftrace_export_lock);
-
-	add_ftrace_export(&ftrace_exports_list, export);
-
-	mutex_unlock(&ftrace_export_lock);
-
-	return 0;
-}
-EXPORT_SYMBOL_GPL(register_ftrace_export);
-
-int unregister_ftrace_export(struct trace_export *export)
-{
-	int ret;
-
-	mutex_lock(&ftrace_export_lock);
-
-	ret = rm_ftrace_export(&ftrace_exports_list, export);
-
-	mutex_unlock(&ftrace_export_lock);
-
-	return ret;
-}
-EXPORT_SYMBOL_GPL(unregister_ftrace_export);
-
 void
 trace_function(struct trace_array *tr,
 	       unsigned long ip, unsigned long parent_ip, unsigned long flags,
-- 
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[PATCH v3 4/6] tracing: add trace_export support for trace_marker

[Tingwei Zhang]

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

Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/linux/trace.h | 1 +
 kernel/trace/trace.c  | 9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/include/linux/trace.h b/include/linux/trace.h
index 5a01eeffb254..80b7df68bc0f 100644
--- a/include/linux/trace.h
+++ b/include/linux/trace.h
@@ -6,6 +6,7 @@
 
 #define TRACE_EXPORT_FUNCTION	BIT(0)
 #define TRACE_EXPORT_EVENT	BIT(1)
+#define TRACE_EXPORT_MARKER	BIT(2)
 
 /*
  * The trace export - an export of Ftrace output. The trace_export
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 2f9302a8b322..67993abda394 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -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)
-- 
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[PATCH v3 5/6] stm class: ftrace: enable supported trace export flag

[Tingwei Zhang]

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

Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 drivers/hwtracing/stm/ftrace.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/hwtracing/stm/ftrace.c b/drivers/hwtracing/stm/ftrace.c
index ce868e095410..c694a6e692d1 100644
--- a/drivers/hwtracing/stm/ftrace.c
+++ b/drivers/hwtracing/stm/ftrace.c
@@ -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);
 }
-- 
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[PATCH v3 6/6] stm class: ftrace: use different channel accroding to CPU

[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 <tingwei@codeaurora.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 drivers/hwtracing/stm/ftrace.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/stm/ftrace.c b/drivers/hwtracing/stm/ftrace.c
index c694a6e692d1..ebf29489919c 100644
--- a/drivers/hwtracing/stm/ftrace.c
+++ b/drivers/hwtracing/stm/ftrace.c
@@ -37,8 +37,10 @@ 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);
+	/* This is called from trace system with preemption disabled */
+	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 +65,7 @@ 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");
-- 
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Re: [PATCH v3 6/6] stm class: ftrace: use different channel accroding to CPU

[Alexander Shishkin]

Tingwei Zhang <tingwei@codeaurora.org> writes:

> @@ -63,6 +65,7 @@ static int __init stm_ftrace_init(void)
>  {
>  	int ret;
>  
> +	stm_ftrace.data.nr_chans = num_possible_cpus();

Not a problem with this patch necesarily, but this made me realize that
.nr_chans may be larger than:

 (1) what the policy permits,
 (2) what the stm device can handle.

While (1) the user can fix in the policy, they won't be able to fix (2),
in which case they won't be able to use stm_ftrace at all. I'm thinking
if a link-time callback would be good enough.

Another thing is that .nr_chans needs to be a power of 2 at the moment.

Regards,
--
Alex

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Re: [PATCH v3 6/6] stm class: ftrace: use different channel accroding to CPU

[Tingwei Zhang]

On Fri, Sep 18, 2020 at 08:45:52PM +0800, Alexander Shishkin wrote:
> Tingwei Zhang <tingwei@codeaurora.org> writes:
> 
> > @@ -63,6 +65,7 @@ static int __init stm_ftrace_init(void)
> >  {
> >  	int ret;
> >  
> > +	stm_ftrace.data.nr_chans = num_possible_cpus();
> 
> Not a problem with this patch necesarily, but this made me realize that
> .nr_chans may be larger than:
> 
>  (1) what the policy permits,
>  (2) what the stm device can handle.
> 
> While (1) the user can fix in the policy, they won't be able to fix (2),
> in which case they won't be able to use stm_ftrace at all. I'm thinking
> if a link-time callback would be good enough.
>

Hi Alex,

I'm not sure if I understand this correct. If the nr_chans requested by
stm_ftrace is larger than policy permits or stm device can handle,
stm_assign_first_policy() returns with error so stm_source_link_add()
will fail. User would notice that when link happens.  There's not much
we can do if resource is not enough.
 
> Another thing is that .nr_chans needs to be a power of 2 at the moment.
> 
I'll change to below.
stm_ftrace.data.nr_chans = roundup_pow_of_two(num_possible_cpus());
> Regards,
> --
> Alex
> 
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Re: [PATCH v3 0/6] tracing: export event trace and trace_marker

[Tingwei Zhang]

Hi Alexander, Maxime, Aleandre,

May I know your comments for this patch set?

Thanks,
Tingwei

On Thu, Sep 03, 2020 at 08:17:00AM +0800, Tingwei Zhang wrote:
> Ftrace has ability to export trace packets to other destination.
> 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 separate channel for each CPU to avoid mixing up
> packets
> from different CPUs together.
> 
> Change from v2:
> Change flag definition to BIT(). (Steven)
> Add comment in stm_ftrace_write() to clarify it's safe to use 
> smp_processor_id() here since preempt is disabled. (Steven) 
> 
> Change from v1:
> All changes are suggested by Steven Rostedt.
> User separate 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 |   7 +-
>  include/linux/trace.h          |   7 +
>  kernel/trace/trace.c           | 270 ++++++++++++++++++---------------
>  4 files changed, 159 insertions(+), 127 deletions(-)
> 
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
> 

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Re: [PATCH v3 0/6] tracing: export event trace and trace_marker

[Alexander Shishkin]

Tingwei Zhang <tingweiz@codeaurora.org> writes:

> Hi Alexander, Maxime, Aleandre,
>
> May I know your comments for this patch set?

Everything except the last patch is

Reviewed-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>

After that one is resolved either I can pick it up or Stephen. Either
way is fine with me.

Regards,
--
Alex

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