Re: it isn't aa's rwsem-generic-6 bug but something else [Re: aa's rwsem-generic-6 bug? Process stuck in 'R' state.]

From: Andrea Arcangeli (
Date: Thu Apr 26 2001 - 10:45:53 EST

On Thu, Apr 26, 2001 at 12:38:02AM -0500, Bob McElrath wrote:
> When I posted this bug originally, you came right out and said it was
> probably the rwsemaphores. I really have no idea how the rwsemaphores

You were talking about the ps table hang when I told you about the rwsem
races. I had the same trouble on my alpha and I reproduced the races
trivially by lanucing:

        make MAKE='make -j2' -j2 &

        while :; do ps xa ; sleep 1 ; done

After a few seconds ps deadlocked. Try that on the old asm semaphores.

It was 100% reproducible, and after I rewrote the rwsemaphores the
deadlock gone away completly.

Your X hanging in R state is completly unrelated to the rwsem ps table
hang problem as far I can tell.

> I'm running a debug X build at this point, and have identified at least

If you can reproduce without starting X I will be interested in fixing
the hang. Maybe you have a graphics card with a fb driver that doesn't
need VESA that maybe works on the alpha, then you could run X without
privilegies. (btw, in theory we could make the VESA thing working as
well using the x86 emulator in SRM but nobody attempted to implement
that yet)

> instead of gcc...then figured what the hell) The rest were with egcs
> 1.1.2. I'll use egcs 1.1.2 in the future.


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