Re: [patch] increase spinlock-debug looping timeouts (write_lock and NMI)

[Dave Olson <olson@unixfolk.com>]

On Fri, 23 Jun 2006, Ingo Molnar wrote:
| we really need to figure out what's happening here! Could you re-enable 
| spinlock debugging and try the patch below - do the stalls/lockups still 
| happen?

I'll do that, but the 2.6.16 FC4 kernel already has cpu_relax()
rather than __delay(1), so I'm about 95% certain that this patch
isn't going to help anything.   The NMI watchdog will still fire,
because all we are going to do is wait even longer, etc.

| ===================================================================
| --- linux.orig/lib/spinlock_debug.c
| +++ linux/lib/spinlock_debug.c
| @@ -104,10 +104,10 @@ static void __spin_lock_debug(spinlock_t
|  	u64 i;
|  
|  	for (;;) {
| -		for (i = 0; i < loops_per_jiffy * HZ; i++) {
| +		for (;;) {
|  			if (__raw_spin_trylock(&lock->raw_lock))
|  				return;
| -			__delay(1);
| +			cpu_relax();
|  		}

etc.

Dave Olson
olson@unixfolk.com
http://www.unixfolk.com/dave
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