module: don't use stop_machine for waiting rmmod

rmmod has a little-used "-w" option, meaning that instead of failing if the module is in use, it should block until the module becomes unused. In this case, we don't need to use stop_machine: Max Krasnyansky indicated that would be useful for SystemTap which loads/unloads new modules frequently. Cc: Max Krasnyansky <maxk@qualcomm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

module: don't use stop_machine for waiting rmmod
rmmod has a little-used "-w" option, meaning that instead of failing if the module is in use, it should block until the module becomes unused. In this case, we don't need to use stop_machine: Max Krasnyansky indicated that would be useful for SystemTap which loads/unloads new modules frequently. Cc: Max Krasnyansky <maxk@qualcomm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Rusty Russell
1 parent 93ded9b8fd
Showing 1 changed file with 11 additions and 4 deletions Side-by-side Diff
kernel/module.c
@@ -639,8 +639,8 @@
 {
 	struct stopref *sref = _sref;
  
-	/* If it's not unused, quit unless we are told to block. */
-	if ((sref->flags & O_NONBLOCK) && module_refcount(sref->mod) != 0) {
+	/* If it's not unused, quit unless we're forcing. */
+	if (module_refcount(sref->mod) != 0) {
 		if (!(*sref->forced = try_force_unload(sref->flags)))
 			return -EWOULDBLOCK;
 	}
  
@@ -652,9 +652,16 @@
  
 static int try_stop_module(struct module *mod, int flags, int *forced)
 {
-	struct stopref sref = { mod, flags, forced };
+	if (flags & O_NONBLOCK) {
+		struct stopref sref = { mod, flags, forced };
  
-	return stop_machine_run(__try_stop_module, &sref, NR_CPUS);
+		return stop_machine_run(__try_stop_module, &sref, NR_CPUS);
+	} else {
+		/* We don't need to stop the machine for this. */
+		mod->state = MODULE_STATE_GOING;
+		synchronize_sched();
+		return 0;
+	}
 }
  
 unsigned int module_refcount(struct module *mod)
...	...	@@ -639,8 +639,8 @@
639	639	{
640	640	struct stopref *sref = _sref;
641	641
642		- /* If it's not unused, quit unless we are told to block. */
643		- if ((sref->flags & O_NONBLOCK) && module_refcount(sref->mod) != 0) {
	642	+ /* If it's not unused, quit unless we're forcing. */
	643	+ if (module_refcount(sref->mod) != 0) {
644	644	if (!(*sref->forced = try_force_unload(sref->flags)))
645	645	return -EWOULDBLOCK;
646	646	}
647	647
...	...	@@ -652,9 +652,16 @@
652	652
653	653	static int try_stop_module(struct module mod, int flags, int forced)
654	654	{
655		- struct stopref sref = { mod, flags, forced };
	655	+ if (flags & O_NONBLOCK) {
	656	+ struct stopref sref = { mod, flags, forced };
656	657
657		- return stop_machine_run(__try_stop_module, &sref, NR_CPUS);
	658	+ return stop_machine_run(__try_stop_module, &sref, NR_CPUS);
	659	+ } else {
	660	+ /* We don't need to stop the machine for this. */
	661	+ mod->state = MODULE_STATE_GOING;
	662	+ synchronize_sched();
	663	+ return 0;
	664	+ }
658	665	}
659	666
660	667	unsigned int module_refcount(struct module *mod)