Re: [PATCH] 2.1.88 Hanging Processes (Uninterruptible Sleep)

Linus Torvalds (
Mon, 2 Mar 1998 15:10:33 -0800 (PST)

On Mon, 2 Mar 1998, F Harvell wrote:
> Based on personal observations and from reading the kernel/smp
> lists, the uninterruptible sleep problems appear to be SMP related. It
> is aggravated by the IO-APIC code (which makes a significantly faster
> system) implemented in 2.1.85+. I have added the __asm__ line to the
> four places in kernel 2.1.88 where there is a schedule loop around an
> uninterruptible sleep. This appears to have significantly helped
> reduce my problems with processes getting stuck in the uninterruptible
> sleep mode. The patch is included below. Hope this helps.

Oh, ye Gods. I didn't think the asm patch would _really_ make any
difference, but I was obviusly wrong. That's good news to some degree,
because it does mean that we may have a handle on the problem, and that my
basic suspicion for why it happened was on the right track.

However, the asm patch was only meant to be an aid in figuring out whether
this was really the basic problem: I can't use it in any real kernel if
for no other reason that it obviously works only on x86. I'll have to come
up with something better that is portable.

Anyway, thanks for the feedback, and it is interesting that this actually
does make a difference. I think I have an idea on how to possibly fix


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