Re: generic rwsem [Re: Alpha "process table hang"]

[Andrea Arcangeli <andrea@suse.de>]

On Mon, Apr 23, 2001 at 06:27:23PM -0500, Bob McElrath wrote:
> Well, take that back, I just got it to hang.  Again, this is 2.4.4pre3
> with alpha-numa-3 and rwsem-generic-4.  I saw it upon starting mozilla.
> I also saw some scary filesystem errors that may or may not be related:
>     Apr 23 18:09:40 draal kernel: EXT2-fs error (device sd(8,2)): 
>         ext2_new_block: Free blocks count corrupted for block group 252 

That is probably unrelated to the ps hang. I suspect you are been bitten by the
ext2 metadata corruption (2.4.4pre2 was just fixed but previous kernel wasn't).

> rwsem-generic-6 is the latest from Andrea, I'll build a new 2.4.4pre4
> kernel with these patches and let you know the results.  Have you made

Yes, that's safe.

> changes between rwsem-generic-4 and rwsem-generic-6 that would
> fix/prevent a deadlock?

No, but I think they are two separate issues.

> Let me know if there are any useful tests I could perform.  Would it be
> useful for me to run the rwsem benchmarks you've been using?  Could
> these detect a deadlock situation?

yes to be sure you can run it without my patch and see if it hangs (I never
tried that myself, but I was able to reproduce the ps hang quite easily and it
was quite obviously due the rwsemaphores and it gone away completly after I
used the generic semaphores).

Andrea