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: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4BA97FA7.6040406@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

3 files changed, 10 insertions, 13 deletions

diff --git a/include/linux/module.h b/include/linux/module.h
index 5e869ffd34aa..393ec39b580a 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -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;
diff --git a/include/trace/events/module.h b/include/trace/events/module.h
index 4b0f48ba16a6..a585f8135bd9 100644
--- a/include/trace/events/module.h
+++ b/include/trace/events/module.h
@@ -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,
diff --git a/kernel/module.c b/kernel/module.c
index c968d3606dca..21591ad921f3 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -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);