Message-Id: <1193774725.24087.303.camel@localhost>
Date:	Tue, 30 Oct 2007 13:05:25 -0700
From:	Dave Hansen <haveblue@...ibm.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@....de>
Subject: fix marker warnings

I'm seeing these in the latest git:

kernel/marker.c: In function `marker_probe_unregister':
kernel/marker.c:355: warning: `probe_module' might be used uninitialized in this function
kernel/marker.c: In function `marker_probe_unregister_private_data':
kernel/marker.c:389: warning: `probe_module' might be used uninitialized in this function
kernel/marker.c:392: warning: `entry' might be used uninitialized in this function

It's due to gcc not detecting that the need_update condition is actually
constant, and will never call marker_update_probes() on an uninitialized
probe_module.

However, that need_update bit is all due to dropping the mutex before
calling marker_update_probes().  As far as I can tell, every call to
marker_update_probes() has this lock dropping behavior just before
calling it.  So, let's just hold the locks over the
marker_update_probes() and document that it needs to have a lock taken
instead.  

This removes code overall.  Untested except for a quick compile.
Consider it just a style suggestion. :)

marker_probe_unregister_private_data() also has a bit of a goto mess
that produces similar warnings.  I'll look at it next.

---

 linux-2.6.git-dave/kernel/marker.c |   34 +++++++++++-----------------------
 1 file changed, 11 insertions(+), 23 deletions(-)

diff -puN kernel/marker.c~fix-marker-warnings kernel/marker.c
--- linux-2.6.git/kernel/marker.c~fix-marker-warnings	2007-10-30 12:54:36.000000000 -0700
+++ linux-2.6.git-dave/kernel/marker.c	2007-10-30 13:03:39.000000000 -0700
@@ -288,12 +288,13 @@ void marker_update_probe_range(struct ma
  * Issues a synchronize_sched() when no reference to the module passed
  * as parameter is found in the probes so the probe module can be
  * safely unloaded from now on.
+ *
+ * must hold markers_mutex
  */
-static void marker_update_probes(struct module *probe_module)
+static void __marker_update_probes(struct module *probe_module)
 {
 	int refcount = 0;
 
-	mutex_lock(&markers_mutex);
 	/* Core kernel markers */
 	marker_update_probe_range(__start___markers,
 			__stop___markers, probe_module, &refcount);
@@ -303,7 +304,6 @@ static void marker_update_probes(struct 
 		synchronize_sched();
 		deferred_sync = 0;
 	}
-	mutex_unlock(&markers_mutex);
 }
 
 /**
@@ -320,7 +320,7 @@ 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 +335,9 @@ int marker_probe_register(const char *na
 	ret = add_marker(name, format, probe, private);
 	if (ret)
 		goto end;
-	need_update = 1;
+	__marker_update_probes(NULL);
 end:
 	mutex_unlock(&markers_mutex);
-	if (need_update)
-		marker_update_probes(NULL);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(marker_probe_register);
@@ -355,7 +353,6 @@ 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 +365,9 @@ 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;
+	__marker_update_probes(probe_module);
 end:
 	mutex_unlock(&markers_mutex);
-	if (need_update)
-		marker_update_probes(probe_module);
 	return private;
 }
 EXPORT_SYMBOL_GPL(marker_probe_unregister);
@@ -392,7 +387,6 @@ 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 +408,9 @@ iter_end:
 	probe_module = __module_text_address((unsigned long)entry->probe);
 	private = remove_marker(entry->name);
 	deferred_sync = 1;
-	need_update = 1;
+	__marker_update_probes(probe_module);
 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 +426,7 @@ 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 +439,9 @@ int marker_arm(const char *name)
 	 */
 	if (entry->refcount++)
 		goto end;
-	need_update = 1;
 end:
+	__marker_update_probes(NULL);
 	mutex_unlock(&markers_mutex);
-	if (need_update)
-		marker_update_probes(NULL);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(marker_arm);
@@ -467,7 +457,7 @@ 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 +476,9 @@ int marker_disarm(const char *name)
 		ret = -EPERM;
 		goto end;
 	}
-	need_update = 1;
 end:
+	__marker_update_probes(NULL);
 	mutex_unlock(&markers_mutex);
-	if (need_update)
-		marker_update_probes(NULL);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(marker_disarm);
_


-- Dave

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