Re: [patch] increase spinlock-debug looping timeouts from 1 sec to1 min

[Andrew Morton]

On Mon, 19 Jun 2006 09:02:29 +0200
Ingo Molnar <mingo@xxxxxxx> wrote:

> Subject: increase spinlock-debug looping timeouts from 1 sec to 1 min

But it's broken.  In the non-debug case we subtract RW_LOCK_BIAS so we know
that the writer will get the lock when all readers vacate.  But in the
CONFIG_DEBUG_SPINLOCK case we don't do that, with the result that taking a
write_lock can take over a second.

A much, much better fix (which involves visiting all architectures) would
be to subtract RW_LOCK_BIAS and _then_ wait for a second.

OK, it's only debug code.  But RH (for one) have decided to ship zillions
of kernels with this debug code turned on.
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