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

[Greg KH]

On Thu, Jun 12, 2003 at 04:16:03PM -0700, 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.

Doh, I ate too much for lunch today and need to wake up...

Pat, here's an updated patch.

thanks,

greg k-h

diff -Nru a/lib/kobject.c b/lib/kobject.c
--- a/lib/kobject.c	Thu Jun 12 16:21:21 2003
+++ b/lib/kobject.c	Thu Jun 12 16:21:21 2003
@@ -100,6 +100,8 @@
 
 #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)
 {
@@ -151,6 +153,12 @@
 
 	envp [i++] = scratch;
 	scratch += sprintf(scratch, "ACTION=%s", action) + 1;
+
+	spin_lock(&sequence_lock);
+	envp [i++] = scratch;
+	scratch += sprintf(scratch, "SEQNUM=%ld", sequence_num) + 1;
+	++sequence_num;
+	spin_unlock(&sequence_lock);
 
 	kobj_path_length = get_kobj_path_length (kset, kobj);
 	kobj_path = kmalloc (kobj_path_length, GFP_KERNEL);