Tracepoint: Dissociate from module mutex

Copy the information needed from struct module into a local module list
held within tracepoint.c from within the module coming/going notifier.

This vastly simplifies locking of tracepoint registration /
unregistration, because we don't have to take the module mutex to
register and unregister tracepoints anymore. Steven Rostedt ran into
dependency problems related to modules mutex vs kprobes mutex vs ftrace
mutex vs tracepoint mutex that seems to be hard to fix without removing
this dependency between tracepoint and module mutex. (note: it should be
investigated whether kprobes could benefit of being dissociated from the
modules mutex too.)

This also fixes module handling of tracepoint list iterators, because it
was expecting the list to be sorted by pointer address. Given we have
control on our own list now, it's OK to sort this list which has
tracepoints as its only purpose. The reason why this sorting is required
is to handle the fact that seq files (and any read() operation from
user-space) cannot hold the tracepoint mutex across multiple calls, so
list entries may vanish between calls. With sorting, the tracepoint
iterator becomes usable even if the list don't contain the exact item
pointed to by the iterator anymore.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Jason Baron <jbaron@redhat.com>
CC: Ingo Molnar <mingo@elte.hu>
CC: Lai Jiangshan <laijs@cn.fujitsu.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Link: http://lkml.kernel.org/r/20110810191839.GC8525@Krystal
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 11 insertions, 14 deletions

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index d530a44..df0a779 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -54,8 +54,18 @@ extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
 						void *data);
 extern void tracepoint_probe_update_all(void);
 
+#ifdef CONFIG_MODULES
+struct tp_module {
+	struct list_head list;
+	unsigned int num_tracepoints;
+	struct tracepoint * const *tracepoints_ptrs;
+};
+#endif /* CONFIG_MODULES */
+
 struct tracepoint_iter {
-	struct module *module;
+#ifdef CONFIG_MODULES
+	struct tp_module *module;
+#endif /* CONFIG_MODULES */
 	struct tracepoint * const *tracepoint;
 };
 
@@ -63,8 +73,6 @@ extern void tracepoint_iter_start(struct tracepoint_iter *iter);
 extern void tracepoint_iter_next(struct tracepoint_iter *iter);
 extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
 extern void tracepoint_iter_reset(struct tracepoint_iter *iter);
-extern int tracepoint_get_iter_range(struct tracepoint * const **tracepoint,
-	struct tracepoint * const *begin, struct tracepoint * const *end);
 
 /*
  * tracepoint_synchronize_unregister must be called between the last tracepoint
@@ -78,17 +86,6 @@ static inline void tracepoint_synchronize_unregister(void)
 
 #define PARAMS(args...) args
 
-#ifdef CONFIG_TRACEPOINTS
-extern
-void tracepoint_update_probe_range(struct tracepoint * const *begin,
-	struct tracepoint * const *end);
-#else
-static inline
-void tracepoint_update_probe_range(struct tracepoint * const *begin,
-	struct tracepoint * const *end)
-{ }
-#endif /* CONFIG_TRACEPOINTS */
-
 #endif /* _LINUX_TRACEPOINT_H */
 
 /*