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tracing: add protection around module events unload

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When reading the trace buffer, there is a race that when a module
is unloaded it removes events that is stilled referenced in the buffers.
This patch adds the protection around the unloading of the events
from modules and the reading of the trace buffers.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2009-06-09 17:29:07 -04:00 • committed by Steven Rostedt
parent 725c624a58
commit 110bf2b764
3 changed files with 19 additions and 4 deletions
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15
kernel/trace/trace_output.c
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@ -14,7 +14,7 @@
/* must be a power of 2 */
#define EVENT_HASHSIZE 128
static DECLARE_RWSEM(trace_event_mutex);
DECLARE_RWSEM(trace_event_mutex);
DEFINE_PER_CPU(struct trace_seq, ftrace_event_seq);
EXPORT_PER_CPU_SYMBOL(ftrace_event_seq);
@ -702,6 +702,16 @@ int register_ftrace_event(struct trace_event *event)
}
EXPORT_SYMBOL_GPL(register_ftrace_event);
/*
* Used by module code with the trace_event_mutex held for write.
*/
int __unregister_ftrace_event(struct trace_event *event)
{
hlist_del(&event->node);
list_del(&event->list);
return 0;
}
/**
* unregister_ftrace_event - remove a no longer used event
* @event: the event to remove
@ -709,8 +719,7 @@ EXPORT_SYMBOL_GPL(register_ftrace_event);
int unregister_ftrace_event(struct trace_event *event)
{
down_write(&trace_event_mutex);
hlist_del(&event->node);
list_del(&event->list);
__unregister_ftrace_event(event);
up_write(&trace_event_mutex);
return 0;