Re: Spinlocks waiting with interrupts disabled / preempt disabled.
From: Ingo Molnar
Date: Wed May 07 2008 - 03:30:54 EST
* Christoph Lameter <clameter@xxxxxxx> wrote:
> @@ -132,10 +132,14 @@ unsigned long __lockfunc _write_lock_irq
> {
> unsigned long flags;
>
> +retry:
> local_irq_save(flags);
> - preempt_disable();
> - _raw_write_lock(lock);
> - return flags;
> + if (_write_trylock(lock))
> + return flags;
> + local_irq_restore(flags);
> + while (!write_can_lock(lock))
> + cpu_relax();
> + goto retry;
> }
> EXPORT_SYMBOL(_write_lock_irqsave);
hm, this is done on a too high level and will turn off some debugging
code. I.e. if we dont just loop long but truly deadlock here we wont
call lib/spinlock_debug.c's _raw_write_lock() code that does some sanity
checks in the debug case.
so how about doing this on a deeper level and adding a new
__raw_write_lock_flags() primitive that would look at the flags value
and could enable interrupts in the lowlevel code?
Ingo
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