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Tracepoint: Dissociate from module mutex

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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>
This commit is contained in:
Mathieu Desnoyers 2011-08-10 15:18:39 -04:00 • committed by Steven Rostedt
parent 3a301d7c1c
commit b75ef8b44b
4 changed files with 158 additions and 95 deletions
Download patch file Download diff file Expand all files Collapse all files

12
include/linux/module.h
View file

@ -580,9 +580,6 @@ int unregister_module_notifier(struct notifier_block * nb);
extern void print_modules(void);
extern void module_update_tracepoints(void);
extern int module_get_iter_tracepoints(struct tracepoint_iter *iter);
#else /* !CONFIG_MODULES... */
#define EXPORT_SYMBOL(sym)
#define EXPORT_SYMBOL_GPL(sym)
@ -698,15 +695,6 @@ static inline int unregister_module_notifier(struct notifier_block * nb)
static inline void print_modules(void)
{
}
static inline void module_update_tracepoints(void)
{
}
static inline int module_get_iter_tracepoints(struct tracepoint_iter *iter)
{
return 0;
}
#endif /* CONFIG_MODULES */
#ifdef CONFIG_SYSFS