Re: Spinlocks waiting with interrupts disabled / preempt disabled.

[Christoph Lameter]

On Wed, 7 May 2008, Ingo Molnar wrote:

> > +		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.

Right. I guessed that given the gazillion helper functions and wanted to 
know how to address this in the right way.

> 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?

Ok will look at that. Note that this is not unique to _write_lock_irqsave 
but all other locks that disable interrupts seem to have the same issue. 

We are likely going to duplicate a lot of functions.


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