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

[Bob McElrath <mcelrath+linux@draal.physics.wisc.edu>]

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Andrea Arcangeli [andrea@suse.de] wrote:
> On Thu, Apr 19, 2001 at 11:21:17AM -0500, Bob McElrath wrote:
> > I'm at 2 days uptime now, and have not seen the process-table-hang.
> > Looks like this fixed it.  Previously I would get a hang in the first
> > day or so.  I'm using your alpha-numa-3 and rwsem-generic-4 against
> > 2.4.4pre3.
> 
> good, thanks for the report.
> 
> BTW, if you upgrade to 2.4.4pre4 you can apply those two patches:
> 
> 	ftp://ftp.us.kernel.org/pub/linux/kernel/people/andrea/kernels/v2.4/2.4.4pre4aa1/00_alpha-numa-4
> 	ftp://ftp.us.kernel.org/pub/linux/kernel/people/andrea/kernels/v2.4/2.4.4pre4aa1/00_rwsem-generic-6
> 
> really the first is not necessary anymore unless you're using a wildfire. The
> second also resurrect the optimized rwsemaphores for all archs but alpha and
> ia32.

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 

There has been a lot of discussion on the topic of rwsems (that,
admittedly, I haven't followed very closely).  It looks like
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
changes between rwsem-generic-4 and rwsem-generic-6 that would
fix/prevent a deadlock?

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?

Cheers,
-- Bob

Bob McElrath (rsmcelrath@students.wisc.edu) 
Univ. of Wisconsin at Madison, Department of Physics

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