svn commit: r192604 - in user/kmacy/releng_7_2_fcs/sys: dev/hwpmc sys

[Kip Macy]

On Tue, May 26, 2009 at 5:30 AM, John Baldwin <jhb at freebsd.org> wrote:
> On Friday 22 May 2009 5:45:43 pm Kip Macy wrote:
>> Author: kmacy
>> Date: Fri May 22 21:45:43 2009
>> New Revision: 192604
>> URL: http://svn.freebsd.org/changeset/base/192604
>>
>> Log:
>>   - remove pmc_kthread_mtx
>>   - replace sleep/wakeup on kthread with a condvar
>
> If you do not sleep on the kthread/kproc when waiting for a kthread to
> exit, then you open up a race window.  Usually this matters more for
> any kthreads that live in a module since the race allows the module to
> be unmapped before the thread is finished executing code from the module
> resulting in a fatal page fault in the kernel.


Yes, that is why the kthread explicitly calls cv_signal after clearing
the kthread pointer.

Thanks,
Kip