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

Patrick Mochel
2003-06-12T23:11:11Z

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);