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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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