[PATCH] Immediate Value - Architecture Independent Code Deferred Sync

Mathieu Desnoyers
2007-07-14T23:52:53Z

Linux Kernel Markers - Architecture Independent Code Deferred Sync

Upon marker probe_unregister, we delay call to synchronize_sched() to
accelerate mass unregistration (only when there is no more reference to a
give module do we call synchronize_sched()). However, we need to make sure
every critical region have ended before we re-arm a marker that has been
unregistered and then registered back with a different probe data.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Christoph Hellwig <hch@infradead.org>
---
kernel/marker.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)

Index: linux-2.6-lttng/kernel/marker.c
===================================================================
--- linux-2.6-lttng.orig/kernel/marker.c 2007-07-14 19:38:11.000000000 -0400
+++ linux-2.6-lttng/kernel/marker.c 2007-07-14 19:46:25.000000000 -0400
@@ -30,11 +30,21 @@ extern struct __mark_marker __stop___mar

/*
* module_mutex nests inside markers_mutex. Markers mutex protects the builtin
- * and module markers, and the hash table.
+ * and module markers, the hash table and deferred_sync.
*/
DEFINE_MUTEX(markers_mutex);

/*
+ * Marker deferred synchronization.
+ * Upon marker probe_unregister, we delay call to synchronize_sched() to
+ * accelerate mass unregistration (only when there is no more reference to a
+ * give module do we call synchronize_sched()). However, we need to make sure
+ * every critical region have ended before we re-arm a marker that has been
+ * unregistered and then registered back with a different probe data.
+ */
+static int deferred_sync;
+
+/*
* Marker hash table, containing the active markers.
* Protected by module_mutex.
*/
@@ -303,8 +313,10 @@ static inline void __marker_update_probe
__stop___markers, probe_module, &refcount);
/* Markers in modules. */
__marker_update_probes_modules(probe_module, &refcount);
- if (probe_module && refcount == 0)
+ if (probe_module && refcount == 0) {
synchronize_sched();
+ deferred_sync = 0;
+ }
}

#ifdef CONFIG_MODULES
@@ -353,6 +365,10 @@ int marker_probe_register(const char *na
ret = -EBUSY;
goto end;
}
+ if (deferred_sync) {
+ synchronize_sched();
+ deferred_sync = 0;
+ }
ret = _add_marker(name, format, probe, pdata);
if (ret)
goto end;
@@ -384,6 +400,7 @@ void *marker_probe_unregister(const char
/* In what module is the probe handler ? */
probe_module = __module_text_address((unsigned long)entry->probe);
pdata = _remove_marker(name);
+ deferred_sync = 1;
_marker_update_probes(probe_module);
end:
mutex_unlock(&markers_mutex);
@@ -425,6 +442,7 @@ iter_end:
/* In what module is the probe handler ? */
probe_module = __module_text_address((unsigned long)entry->probe);
pdata = _remove_marker(entry->name);
+ deferred_sync = 1;
_marker_update_probes(probe_module);
end:
mutex_unlock(&markers_mutex);