Re: contention on profile_lock

[John Levon <levon@movementarian.org>]

On Thu, Nov 04, 2004 at 12:49:21PM -0800, Jesse Barnes wrote:

> John pointed out that this breaks modules.  Would registering and 
> unregistering a function pointer thus be module safe?  Dipankar, hopefully 
> you have something better?
> 
> static int timer_start(void)
> {
>  /* Setup the callback pointer */
>  oprofile_timer_notify = oprofile_timer;
>  return 0;
> }

Surely something like (profile.c):

funcptr_t timer_hook;

static int register_timer_hook(funcptr_t hook)
{
	if (timer_hook)
		return -EBUSY;
	timer_hook = hook;
}

static void unregister_timer_hook(funcptr_t hook)
{
	WARN_ON(hook != timer_hook);
	timer_hook = NULL;
	/* make sure all CPUs see the NULL hook */
	synchronize_kernel();
}

john