help with SMP debugging...task struct corruption

["Christopher Friesen" <cfriesen@nortel.com>]

I'm running a customized 2.6.10 and seeing some interesting behaviour. 
Based on some additional debugging that we added, the "p->signal" member 
is being set to NULL between the time we call spin_lock() and the time 
we return from it.

Anyone have any ideas what might be going on?  It seems to go away if we 
boot with only 1 cpu.  I assume that some other cpu already holds that 
lock and does something while holding it that causes the "p->signal" 
member to become NULL.


void release_task(struct task_struct * p)
{
	int zap_leader;
	task_t *leader;
	struct dentry *proc_dentry;

repeat:
	atomic_dec(&p->user->processes);
	spin_lock(&p->proc_lock);
	proc_dentry = proc_pid_unhash(p);



Thanks,

Chris