On 5/12/11 6:55 AM, Stanislav Sedov wrote:
On Thu, 12 May 2011 13:43:58 +0300
Andriy Gapon<a...@freebsd.org> mentioned:
Theory:
- smp_rv_waiters[2] becomes equal to smp_rv_ncpus
- [at least] one slave CPU is still in the last call to cpu_spinwait() in
smp_rendezvous_action()
- master CPU notices that the condition is true, exits smp_rendezvous_cpus() and
calls it again
- the slave CPU is still in spinwait
- the master CPU resets smp_rv_waiters[2] to zero
- the slave CPU exits spinwait, see smp_rv_waiters[2] with zero value
- endless loop
That might explain it.
Do you have a patch for me to try?
Thanks!
The NetApp folks working on BHyVe also ran into this. They have a fix
that I think sounds reasonable which is to add a generation count to the
smp rendezvous "structure" and have waiting CPUs stop waiting if the
generation count changes.
--
John Baldwin
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