Re: [Linux-ia64] Hard "hangs" with 2.4.16

Jack Steiner
2001-12-10T21:06:41Z

>
> Anybody else been seeing hangs with 2.4.16+ia64-1128.diff?
>
> I'm running on 4x Lions, some with B3's and some with C0's.
> The BIOS revision is 83B. I have seen the hang on at least
> 4 of the systems. This is a hard hang, no kb interrupts, so
> kdb doesn't help. I don't have much to go on yet. The hangs
> occur in random places, sometimes at various places during
> boot and sometimes after the system has been up for a few
> minutes. I put an ITP (American Arium) on one of the failing
> systems and it didn't fail. Stayed up all night. I moved the
> ITP to another failing system and was able to catch 1
> occurrence of a "hang". I'm still trying to characterize this
> hang to determine whether this is the same thing I am seeing
> on the other systems or just a hardware (configuration) problem.
> What I saw from the ITP was that all of the processors had
> apparently reset (all of their IPs had returned to the reset
> vector, 0x80000000FFFFFF90 (I did have the ITP set to break on
> reset, but it didn't trigger). Not much else to go on, since I
> couldn't even dump any useful processor context.

We saw the same symptom & tracked it down to a bug in the
write_unlock() macro. The result was a memory-ordering problem
that caused the "unlock" of the tasklist_lock to be made
globally visible before the "store's" to the link fields were
visible. The result was a closed loop in the tasklist links.

Try adding a barrier operation BEFORE the clear_bit.

OLD
#define write_unlock(x) ({clear_bit(31, (x)); mb();})

NEW
#define write_unlock(x) ({smp_mb__before_clear_bit(); clear_bit(31, (x));})

This has been fixed in a later version of the IA64 patch.

>
> Anyone else seeing this sort of odd behavior with 2.4.16 on
> Intel Lion SDVs?
>
>
> Thanks,
>
> Chris McDermott
>
>
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>

--
Thanks

Jack Steiner (651-683-5302) (vnet 233-5302) steiner@sgi.com