Re: [patch] increase spinlock-debug looping timeouts (write_lockand NMI)

[Andrew Morton]

On Tue, 20 Jun 2006 17:37:32 +1000
Nick Piggin <nickpiggin@xxxxxxxxxxxx> wrote:

> >>Kernel panic - not syncing: nmi watchdog 
> 
> Any ideas what it might be waiting on?

Readers, I guess.  When there's a spinning writer, nothing prevents _new_
readers from getting into the read-locked region.  If we have enough
readers and the read-locked region is long enough, there's always at least
one reader in the read-locked region and the writer is permanently starved.

> Otherwise, a straight rwlock->spinlock conversion will have a few more
> scalability issues, but I'd guess it wouldn't be a problem  at all for
> most workloads on most systems.

It beats crashing.
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