Re: 2.6.17-1.2145_FC5 mmap-related soft lockup

From: Andrew Morton
Date: Wed Jul 19 2006 - 00:09:20 EST

On Tue, 18 Jul 2006 19:25:16 -0700
"Gary Funck" <gary@xxxxxxxxxxxx> wrote:

> >
> > Are you able to confirm that setting CONFIG_DEBUG_SPINLOCK=n fixes it?
> >
> > And are you able to get us a copy of that test app?
> Yes, I just ran the test with With CONFIG_DEBUG_SPINLOCK=y
> the test fails and the soft lockup situation often results.
> However, when built with CONFIG_DEBUG_SPINLOCK=n, the test passes,
> and runs rather quickly in comparison to when it fails.
> I've attached a slightly updated version of the test case.
> It is a little more carefully crafted and prints some
> output so that you have some idea that it is working.

That's great, thanks. That pretty much confirms that this long-standing
box-killing rwlock starvation bug is specific to Opterons. Neither Ingo
nor I have Opteron machines so a fix will take a little longer than one
would expect.

Meanwhile, an appropriate workaround is to disable CONFIG_DEBUG_SPINLOCK.
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