On 5/12/11 7:05 AM, Andriy Gapon wrote:
on 12/05/2011 13:55 John Baldwin said the following:
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.
This is an adaption of my patch in xcpu branch to head (not tested):
Hmmm, this might be interesting. I think you want to always wait for
this though even if you have a teardown function.
--
John Baldwin
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