Re: [2.4.17/18pre] VM and swap - it's really unusable

Jussi Laako
2002-01-14T22:23:14Z

Alan Cox wrote:
>
> > > In eepro100.c, wait_for_cmd_done() can busywait for one millisecond
> > > and is called multiple times under spinlock.
> >
> > Did I get that right, as long as spinlocked no sense in
> > conditional_schedule()
>
> No conditional schedule, no pre-emption. You would need to rewrite that
> code to do something like try for 100uS then queue a 1 tick timer to
> retry asynchronously. That makes the code vastly more complex for an
> error case and for some drivers where irq mask is required during reset
> waits won't help.

That wait_for_cmd_done() and similar functions in other drivers are called
let's say 3 times in interrupt handler or spinlocked routine and 20 times in
non-interrupts disabled nor spinlocked functions.

Spinlocked reqions are usually protected by spin_lock_irqsave().

So the code reads

if (!spin_is_locked(sl))
conditional_schedule();

This doesn't make the whole problem go away, but could make the situation a
little bit better for most of the time?

- Jussi Laako

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