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