Re: {interruptible_,}sleep_on question

Andreas Bombe (andreas.bombe@munich.netsurf.de)
Mon, 1 Nov 1999 21:30:54 +0100

On Mon, Nov 01, 1999 at 11:28:18AM -0500, Richard B. Johnson wrote:
> On Mon, 1 Nov 1999, Manfred Spraul wrote:
>
> > Is it correct that drivers which call {interruptible_,}sleep_on can miss
> > wakeup events unless they either own the big kernel lock or the
> > global-cli lock before calling sleep_on()?
> >
> [SNIPPED]
>
> The opposite. Nobody can sleep if a global lock is held or the interrupts
> are disabled. To do so is death.

The big kernel lock (as opposed to the standard spinlocks) is released
on schedule and reaquired when control returns. IIRC, the same happens
for disabled IRQs (enabled on schedule, disabled on return).

Nevertheless, a simple, bare sleep_on is rarely useful for hardware
programming.

-- 
    Andreas E. Bombe <andreas.bombe@munich.netsurf.de>
    http://home.pages.de/~andreas.bombe/
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