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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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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