Commit ae832d1e authored by Li Zefan's avatar Li Zefan Committed by Steven Rostedt
Browse files

tracing: Remove side effect from module tracepoints that caused a GPF 



Remove the @refcnt argument, because it has side-effects, and arguments with
side-effects are not skipped by the jump over disabled instrumentation and are
executed even when the tracepoint is disabled.

This was also causing a GPF as found by Randy Dunlap:

Subject: 2.6.33 GP fault only when built with tracing
LKML-Reference: <4BA2B69D.3000309@oracle.com>

Note, the current 2.6.34-rc has a fix for the actual cause of the GPF,
but this fixes one of its triggers.

Tested-by: default avatarRandy Dunlap <randy.dunlap@oracle.com>
Acked-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4BA97FA7.6040406@cn.fujitsu.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 50354a8a

include/linux/module.h

+2 −4
Original line number Diff line number Diff line
@@ -460,8 +460,7 @@ static inline void __module_get(struct module *module) 
	if (module) {

		preempt_disable();

		__this_cpu_inc(module->refptr->count);

		trace_module_get(module, _THIS_IP_,

				 __this_cpu_read(module->refptr->count));

		trace_module_get(module, _THIS_IP_);

		preempt_enable();

	}

}
@@ -475,8 +474,7 @@ static inline int try_module_get(struct module *module) 


		if (likely(module_is_live(module))) {

			__this_cpu_inc(module->refptr->count);

			trace_module_get(module, _THIS_IP_,

				__this_cpu_read(module->refptr->count));

			trace_module_get(module, _THIS_IP_);

		}

		else

			ret = 0;

include/trace/events/module.h

+7 −7
Original line number Diff line number Diff line
@@ -53,9 +53,9 @@ TRACE_EVENT(module_free, 


DECLARE_EVENT_CLASS(module_refcnt,



	TP_PROTO(struct module *mod, unsigned long ip, int refcnt),

	TP_PROTO(struct module *mod, unsigned long ip),



	TP_ARGS(mod, ip, refcnt),

	TP_ARGS(mod, ip),



	TP_STRUCT__entry(

		__field(	unsigned long,	ip		)
@@ -65,7 +65,7 @@ DECLARE_EVENT_CLASS(module_refcnt, 


	TP_fast_assign(

		__entry->ip	= ip;

		__entry->refcnt	= refcnt;

		__entry->refcnt	= __this_cpu_read(mod->refptr->count);

		__assign_str(name, mod->name);

	),
@@ -75,16 +75,16 @@ DECLARE_EVENT_CLASS(module_refcnt, 


DEFINE_EVENT(module_refcnt, module_get,



	TP_PROTO(struct module *mod, unsigned long ip, int refcnt),

	TP_PROTO(struct module *mod, unsigned long ip),



	TP_ARGS(mod, ip, refcnt)

	TP_ARGS(mod, ip)

);



DEFINE_EVENT(module_refcnt, module_put,



	TP_PROTO(struct module *mod, unsigned long ip, int refcnt),

	TP_PROTO(struct module *mod, unsigned long ip),



	TP_ARGS(mod, ip, refcnt)

	TP_ARGS(mod, ip)

);



TRACE_EVENT(module_request,

kernel/module.c

+1 −2
Original line number Diff line number Diff line
@@ -800,8 +800,7 @@ void module_put(struct module *module) 
		preempt_disable();

		__this_cpu_dec(module->refptr->count);



		trace_module_put(module, _RET_IP_,

				 __this_cpu_read(module->refptr->count));

		trace_module_put(module, _RET_IP_);

		/* Maybe they're waiting for us to drop reference? */

		if (unlikely(!module_is_live(module)))

			wake_up_process(module->waiter);

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