Re: problem in md?

Manfred Spraul (manfreds@colorfullife.com)
Tue, 02 Nov 1999 08:58:54 +0100

Ingo Molnar wrote:
> On Tue, 2 Nov 1999, Manfred Spraul wrote:
> > are you aware that do_something() is called WITHOUT the global interrupt
> > lock held?
>
> yep, thanks for pointing this out. I've added asserts to sleep_on() ages
> ago to fix exactly this type of breakage [check out linux-kernel archives
> for sleep_on & cli], but actually forgot to fix this in the RAID code and
> the asserts/warnings got removed from 2.2.
>

Could you add the warning again? I doubt that md is the only place which
relies on the cli()+sleep_on(), eg drivers/block/floppy.c looks
suspicious:
> INT_OFF;
> while (fdc_busy && NO_SIGNAL)
> interruptible_sleep_on(&fdc_wait);
> if (fdc_busy){
> INT_ON;
> return -EINTR;
> }
> fdc_busy = 1;
> INT_ON;

testing and setting fdc_busy is not atomic.

[What about disallowing schedule(), sleep_on() with the global irq lock
held? It's only a band-aid for old drivers, and I'm sure that 90% of
these drivers contain races on SMP, ie I would prefer a clean oops
instead an unexplainable bug report - at least until 2.4pre]

--
	Manfred


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