[PATCH] Synchronous hotplug for kobjects

[PATCH] Synchronous hotplug for kobjects

[Todd Poynor]

As discussed recently, it's expected to be useful to generate
synchronous hotplug events from the kobject subsystem in certain
situations.  This patch adds a kobject_hotplug_wait function that issues
a synchronous call.  The function should be used for appropriate actions
that require synchronous semantics; please note many hotplug events
would suffer severe performance degradation if issued synchronously, and
one should exercise caution in choosing to use this function.

--- linux-2.6.6-orig/include/linux/kobject.h	2004-05-10 11:23:55.000000000 -0700
+++ linux-2.6.6-pm/include/linux/kobject.h	2004-05-10 11:41:25.000000000 -0700
@@ -57,6 +57,7 @@
 extern void kobject_put(struct kobject *);
 
 extern void kobject_hotplug(const char *action, struct kobject *);
+extern void kobject_hotplug_wait(const char *action, struct kobject *);
 
 struct kobj_type {
 	void (*release)(struct kobject *);
--- linux-2.6.6-orig/lib/kobject.c	2004-05-10 11:26:35.000000000 -0700
+++ linux-2.6.6-pm/lib/kobject.c	2004-05-10 13:20:35.389369032 -0700
@@ -104,7 +104,7 @@
 static spinlock_t sequence_lock = SPIN_LOCK_UNLOCKED;
 
 static void kset_hotplug(const char *action, struct kset *kset,
-			 struct kobject *kobj)
+			 struct kobject *kobj, int wait)
 {
 	char *argv [3];
 	char **envp = NULL;
@@ -185,9 +185,9 @@
 		}
 	}
 
-	pr_debug ("%s: %s %s %s %s %s %s %s\n", __FUNCTION__, argv[0], argv[1],
-		  envp[0], envp[1], envp[2], envp[3], envp[4]);
-	retval = call_usermodehelper (argv[0], argv, envp, 0);
+	pr_debug ("%s: %s %s %s %s %s %s %s %d\n", __FUNCTION__, argv[0], argv[1],
+		  envp[0], envp[1], envp[2], envp[3], envp[4], wait);
+	retval = call_usermodehelper (argv[0], argv, envp, wait);
 	if (retval)
 		pr_debug ("%s - call_usermodehelper returned %d\n",
 			  __FUNCTION__, retval);
@@ -199,7 +199,8 @@
 	return;
 }
 
-void kobject_hotplug(const char *action, struct kobject *kobj)
+static void kobject_hotplug_flags(const char *action, struct kobject *kobj,
+				  int wait)
 {
 	struct kobject * top_kobj = kobj;
 
@@ -212,13 +213,27 @@
 	}
 
 	if (top_kobj->kset && top_kobj->kset->hotplug_ops)
-		kset_hotplug(action, top_kobj->kset, kobj);
+		kset_hotplug(action, top_kobj->kset, kobj, wait);
+}
+
+void kobject_hotplug(const char *action, struct kobject *kobj)
+{
+	kobject_hotplug_flags(action, kobj, 0);
+}
+
+void kobject_hotplug_wait(const char *action, struct kobject *kobj)
+{
+	kobject_hotplug_flags(action, kobj, 1);
 }
 #else
 void kobject_hotplug(const char *action, struct kobject *kobj)
 {
 	return;
 }
+void kobject_hotplug_wait(const char *action, struct kobject *kobj)
+{
+	return;
+}
 #endif	/* CONFIG_HOTPLUG */
 
 /**



-- 
Todd Poynor
MontaVista Software

Re: [PATCH] Synchronous hotplug for kobjects

[Greg KH]

On Mon, May 10, 2004 at 01:48:13PM -0700, Todd Poynor wrote:
> As discussed recently, it's expected to be useful to generate
> synchronous hotplug events from the kobject subsystem in certain
> situations.  This patch adds a kobject_hotplug_wait function that issues
> a synchronous call.  The function should be used for appropriate actions
> that require synchronous semantics; please note many hotplug events
> would suffer severe performance degradation if issued synchronously, and
> one should exercise caution in choosing to use this function.

How about I wait until someone really needs this function before adding
it?  Or do you have a patch that does need it?

thanks,

greg k-h

Re: [PATCH] Synchronous hotplug for kobjects

[Todd Poynor]

Greg KH wrote:

> How about I wait until someone really needs this function before adding
> it?  Or do you have a patch that does need it?

I've just sent a patch for system suspend/resume notifiers that uses it. 
If that patch isn't accepted then sounds like this could wait.  Device 
power state change notifiers were also discussed recently, which would 
also use kobject synchronous hotplug if accepted, but the fate of that 
notifier is in doubt.  Thanks -- Todd