Re: [PATCH] udev enhancements to use kernel event queue

[Patrick Mochel]

On 12 Jun 2003, Robert Love wrote:

> On Thu, 2003-06-12 at 16:09, Greg KH wrote:
> 
> > +
> > +	envp [i++] = scratch;
> > +	scratch += sprintf(scratch, "SEQNUM=%ld", sequence_num) + 1;
> > +	++sequence_num;
> 
> Since I do not see a lock in here, I think you need to use atomics?
> 
> As is, you can also race and have the same sequence_num value written
> out twice.

Yeah, how about this ammended patch? 

	-pat

===== lib/kobject.c 1.25 vs edited =====
--- 1.25/lib/kobject.c	Wed Jun 11 12:06:06 2003
+++ edited/lib/kobject.c	Thu Jun 12 16:24:26 2003
@@ -100,6 +100,9 @@
 
 #define BUFFER_SIZE	1024	/* should be enough memory for the env */
 #define NUM_ENVP	32	/* number of env pointers */
+static unsigned long sequence_num;
+static spinlock_t sequence_lock = SPIN_LOCK_UNLOCKED;
+
 static void kset_hotplug(const char *action, struct kset *kset,
 			 struct kobject *kobj)
 {
@@ -112,6 +115,7 @@
 	int kobj_path_length;
 	char *kobj_path = NULL;
 	char *name = NULL;
+	unsigned long seq;
 
 	/* If the kset has a filter operation, call it. If it returns
 	   failure, no hotplug event is required. */
@@ -151,6 +155,13 @@
 
 	envp [i++] = scratch;
 	scratch += sprintf(scratch, "ACTION=%s", action) + 1;
+
+	spin_lock(&sequence_lock);
+	seq = sequence_num++;
+	spin_unlock(&sequence_lock);
+
+	envp [i++] = scratch;
+	scratch += sprintf(scratch, "SEQNUM=%ld", seq) + 1;
 
 	kobj_path_length = get_kobj_path_length (kset, kobj);
 	kobj_path = kmalloc (kobj_path_length, GFP_KERNEL);