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Commit f322e262 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'trace-fixes-v3.15-rc4-v2' of... 

Merge tag 'trace-fixes-v3.15-rc4-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fixes from Steven Rostedt:
 "This contains two fixes.

  The first is a long standing bug that causes bogus data to show up in
  the refcnt field of the module_refcnt tracepoint.  It was introduced
  by a merge conflict resolution back in 2.6.35-rc days.

  The result should be 'refcnt = incs - decs', but instead it did
  'refcnt = incs + decs'.

  The second fix is to a bug that was introduced in this merge window
  that allowed for a tracepoint funcs pointer to be used after it was
  freed.  Moving the location of where the probes are released solved
  the problem"

* tag 'trace-fixes-v3.15-rc4-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracepoint: Fix use of tracepoint funcs after rcu free
  trace: module: Maintain a valid user count
parents d86561b4 8058bd0f

include/trace/events/module.h

+1 −1
Original line number Diff line number Diff line
@@ -80,7 +80,7 @@ DECLARE_EVENT_CLASS(module_refcnt, 


	TP_fast_assign(

		__entry->ip	= ip;

		__entry->refcnt	= __this_cpu_read(mod->refptr->incs) + __this_cpu_read(mod->refptr->decs);

		__entry->refcnt	= __this_cpu_read(mod->refptr->incs) - __this_cpu_read(mod->refptr->decs);

		__assign_str(name, mod->name);

	),

kernel/tracepoint.c

+2 −2
Original line number Diff line number Diff line
@@ -188,7 +188,6 @@ static int tracepoint_add_func(struct tracepoint *tp, 
		WARN_ON_ONCE(1);

		return PTR_ERR(old);

	}

	release_probes(old);



	/*

	 * rcu_assign_pointer has a smp_wmb() which makes sure that the new
@@ -200,6 +199,7 @@ static int tracepoint_add_func(struct tracepoint *tp, 
	rcu_assign_pointer(tp->funcs, tp_funcs);

	if (!static_key_enabled(&tp->key))

		static_key_slow_inc(&tp->key);

	release_probes(old);

	return 0;

}
@@ -221,7 +221,6 @@ static int tracepoint_remove_func(struct tracepoint *tp, 
		WARN_ON_ONCE(1);

		return PTR_ERR(old);

	}

	release_probes(old);



	if (!tp_funcs) {

		/* Removed last function */
@@ -232,6 +231,7 @@ static int tracepoint_remove_func(struct tracepoint *tp, 
			static_key_slow_dec(&tp->key);

	}

	rcu_assign_pointer(tp->funcs, tp_funcs);

	release_probes(old);

	return 0;

}