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

MOLNAR Ingo (mingo@chiara.csoma.elte.hu)
Tue, 3 Mar 1998 22:44:08 +0100 (CET)

> I would think that the problem is not specific to PPro/PII and that the
> good explanation is likely a wrong memory ordering assumption in the
> code rather that intruction reordering. However, I agree that instruction
> re-ordering increases the probability of memory read/write being reordered.

note that those assumptions are perfectly valid on UP. It's just on SMP
that we run IRQ handlers and the kernel in parallel on two or more CPUs,
so such issues start popping up. (and we run kernel code and kernel code
in parallel for more and more subsystems as well)

> So, my thought is that the initial construct that did not force any memory
> ordering was only safe for 386 processors.

it was/is safe on any UP system, and it's also safe on 2.0 SMP.

-- mingo

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