[patch 0/3] Linux Kernel Markers Fixes

[patch 0/3] Linux Kernel Markers Fixes

[Mathieu Desnoyers]

Hi Andrew,

Here are some fixes for the Linux Kernel Markers present in 2.6.24-rc2-git3.
There is a code path (module load) that may update markers without holding the
markers mutex, si I fixed that. The rest is just an tiny documentation
improvement.

The patchset applies on top of 2.6.24-rc2-git3 in this order:

#for -mm
markers-fix-markers-mutex-upon-module-load.patch
markers-document-markers-format-strings.patch
markers-fix-example-format-string.patch

They should be merged in mainline before 2.6.24 final (especially the mutex
fix).

Mathieu

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68

[patch 1/3] Linux Kernel Markers - Fix marker mutex not taken upon module load

[Mathieu Desnoyers]

[-- Attachment #1: markers-fix-markers-mutex-upon-module-load.patch --]
[-- Type: text/plain, Size: 5504 bytes --]

Upon module load, we must take the markers mutex. It implies that the marker
mutex must be nested inside the module mutex.

It implies changing the nesting order : now the marker mutex nests inside the
module mutex. Make the necessary changes to reverse the order in which the
mutexes are taken.

Includes some cleanup from Dave Hansen <haveblue@us.ibm.com>.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---

 kernel/marker.c |   41 +++++++++++++++++------------------------
 1 file changed, 17 insertions(+), 24 deletions(-)

Index: linux-2.6-lttng/kernel/marker.c
===================================================================
--- linux-2.6-lttng.orig/kernel/marker.c	2007-11-13 10:27:22.000000000 -0500
+++ linux-2.6-lttng/kernel/marker.c	2007-11-13 13:34:19.000000000 -0500
@@ -28,7 +28,7 @@ extern struct marker __start___markers[]
 extern struct marker __stop___markers[];
 
 /*
- * module_mutex nests inside markers_mutex. Markers mutex protects the builtin
+ * markers_mutex nests inside module_mutex. Markers mutex protects the builtin
  * and module markers, the hash table and deferred_sync.
  */
 static DEFINE_MUTEX(markers_mutex);
@@ -257,7 +257,6 @@ static void disable_marker(struct marker
  * @refcount: number of references left to the given probe_module (out)
  *
  * Updates the probe callback corresponding to a range of markers.
- * Must be called with markers_mutex held.
  */
 void marker_update_probe_range(struct marker *begin,
 	struct marker *end, struct module *probe_module,
@@ -266,6 +265,7 @@ void marker_update_probe_range(struct ma
 	struct marker *iter;
 	struct marker_entry *mark_entry;
 
+	mutex_lock(&markers_mutex);
 	for (iter = begin; iter < end; iter++) {
 		mark_entry = get_marker(iter->name);
 		if (mark_entry && mark_entry->refcount) {
@@ -281,6 +281,7 @@ void marker_update_probe_range(struct ma
 			disable_marker(iter);
 		}
 	}
+	mutex_unlock(&markers_mutex);
 }
 
 /*
@@ -293,7 +294,6 @@ static void marker_update_probes(struct 
 {
 	int refcount = 0;
 
-	mutex_lock(&markers_mutex);
 	/* Core kernel markers */
 	marker_update_probe_range(__start___markers,
 			__stop___markers, probe_module, &refcount);
@@ -303,7 +303,6 @@ static void marker_update_probes(struct 
 		synchronize_sched();
 		deferred_sync = 0;
 	}
-	mutex_unlock(&markers_mutex);
 }
 
 /**
@@ -320,7 +319,7 @@ int marker_probe_register(const char *na
 			marker_probe_func *probe, void *private)
 {
 	struct marker_entry *entry;
-	int ret = 0, need_update = 0;
+	int ret = 0;
 
 	mutex_lock(&markers_mutex);
 	entry = get_marker(name);
@@ -335,11 +334,11 @@ int marker_probe_register(const char *na
 	ret = add_marker(name, format, probe, private);
 	if (ret)
 		goto end;
-	need_update = 1;
+	mutex_unlock(&markers_mutex);
+	marker_update_probes(NULL);
+	return ret;
 end:
 	mutex_unlock(&markers_mutex);
-	if (need_update)
-		marker_update_probes(NULL);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(marker_probe_register);
@@ -355,7 +354,6 @@ void *marker_probe_unregister(const char
 	struct module *probe_module;
 	struct marker_entry *entry;
 	void *private;
-	int need_update = 0;
 
 	mutex_lock(&markers_mutex);
 	entry = get_marker(name);
@@ -368,11 +366,11 @@ void *marker_probe_unregister(const char
 	probe_module = __module_text_address((unsigned long)entry->probe);
 	private = remove_marker(name);
 	deferred_sync = 1;
-	need_update = 1;
+	mutex_unlock(&markers_mutex);
+	marker_update_probes(probe_module);
+	return private;
 end:
 	mutex_unlock(&markers_mutex);
-	if (need_update)
-		marker_update_probes(probe_module);
 	return private;
 }
 EXPORT_SYMBOL_GPL(marker_probe_unregister);
@@ -392,7 +390,6 @@ void *marker_probe_unregister_private_da
 	struct marker_entry *entry;
 	int found = 0;
 	unsigned int i;
-	int need_update = 0;
 
 	mutex_lock(&markers_mutex);
 	for (i = 0; i < MARKER_TABLE_SIZE; i++) {
@@ -414,11 +411,11 @@ iter_end:
 	probe_module = __module_text_address((unsigned long)entry->probe);
 	private = remove_marker(entry->name);
 	deferred_sync = 1;
-	need_update = 1;
+	mutex_unlock(&markers_mutex);
+	marker_update_probes(probe_module);
+	return private;
 end:
 	mutex_unlock(&markers_mutex);
-	if (need_update)
-		marker_update_probes(probe_module);
 	return private;
 }
 EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data);
@@ -434,7 +431,7 @@ EXPORT_SYMBOL_GPL(marker_probe_unregiste
 int marker_arm(const char *name)
 {
 	struct marker_entry *entry;
-	int ret = 0, need_update = 0;
+	int ret = 0;
 
 	mutex_lock(&markers_mutex);
 	entry = get_marker(name);
@@ -447,11 +444,9 @@ int marker_arm(const char *name)
 	 */
 	if (entry->refcount++)
 		goto end;
-	need_update = 1;
 end:
 	mutex_unlock(&markers_mutex);
-	if (need_update)
-		marker_update_probes(NULL);
+	marker_update_probes(NULL);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(marker_arm);
@@ -467,7 +462,7 @@ EXPORT_SYMBOL_GPL(marker_arm);
 int marker_disarm(const char *name)
 {
 	struct marker_entry *entry;
-	int ret = 0, need_update = 0;
+	int ret = 0;
 
 	mutex_lock(&markers_mutex);
 	entry = get_marker(name);
@@ -486,11 +481,9 @@ int marker_disarm(const char *name)
 		ret = -EPERM;
 		goto end;
 	}
-	need_update = 1;
 end:
 	mutex_unlock(&markers_mutex);
-	if (need_update)
-		marker_update_probes(NULL);
+	marker_update_probes(NULL);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(marker_disarm);

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68

[patch 2/3] Linux Kernel Markers - Document format string

[Mathieu Desnoyers]

[-- Attachment #1: markers-document-markers-format-strings.patch --]
[-- Type: text/plain, Size: 1369 bytes --]

Describes the format string standard further: Use of field names before the type
specifiers..

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---
 Documentation/markers.txt |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Index: linux-2.6-lttng/Documentation/markers.txt
===================================================================
--- linux-2.6-lttng.orig/Documentation/markers.txt	2007-11-11 22:04:50.000000000 -0500
+++ linux-2.6-lttng/Documentation/markers.txt	2007-11-11 22:04:57.000000000 -0500
@@ -35,12 +35,14 @@ In order to use the macro trace_mark, yo
 
 And,
 
-trace_mark(subsystem_event, "%d %s", someint, somestring);
+trace_mark(subsystem_event, "myint %d mystring %s", someint, somestring);
 Where :
 - subsystem_event is an identifier unique to your event
     - subsystem is the name of your subsystem.
     - event is the name of the event to mark.
-- "%d %s" is the formatted string for the serializer.
+- "myint %d mystring %s" is the formatted string for the serializer. "myint" and
+  "mystring" are repectively the field names associated with the first and
+  second parameter.
 - someint is an integer.
 - somestring is a char pointer.
 

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68

[patch 3/3] Linux Kernel Markers - fix samples to follow format string standard

[Mathieu Desnoyers]

[-- Attachment #1: markers-fix-example-format-string.patch --]
[-- Type: text/plain, Size: 1641 bytes --]

Add the field names to marker example format string.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---
 samples/markers/marker-example.c |    3 ++-
 samples/markers/probe-example.c  |    2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

Index: linux-2.6-lttng/samples/markers/marker-example.c
===================================================================
--- linux-2.6-lttng.orig/samples/markers/marker-example.c	2007-11-03 20:56:35.000000000 -0400
+++ linux-2.6-lttng/samples/markers/marker-example.c	2007-11-03 20:57:08.000000000 -0400
@@ -19,7 +19,8 @@ static int my_open(struct inode *inode, 
 {
 	int i;
 
-	trace_mark(subsystem_event, "%d %s", 123, "example string");
+	trace_mark(subsystem_event, "integer %d string %s", 123,
+		"example string");
 	for (i = 0; i < 10; i++)
 		trace_mark(subsystem_eventb, MARK_NOARGS);
 	return -EPERM;
Index: linux-2.6-lttng/samples/markers/probe-example.c
===================================================================
--- linux-2.6-lttng.orig/samples/markers/probe-example.c	2007-11-03 20:57:38.000000000 -0400
+++ linux-2.6-lttng/samples/markers/probe-example.c	2007-11-03 20:57:51.000000000 -0400
@@ -53,7 +53,7 @@ void probe_subsystem_eventb(const struct
 static struct probe_data probe_array[] =
 {
 	{	.name = "subsystem_event",
-		.format = "%d %s",
+		.format = "integer %d string %s",
 		.probe_func = probe_subsystem_event },
 	{	.name = "subsystem_eventb",
 		.format = MARK_NOARGS,

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68