svn commit: r289661 - head/sys/kern

[John Baldwin]

On Tuesday, October 20, 2015 08:29:21 PM Konstantin Belousov wrote:
> Author: kib
> Date: Tue Oct 20 20:29:21 2015
> New Revision: 289661
> URL: https://svnweb.freebsd.org/changeset/base/289661
> 
> Log:
>   Mark struct thread zone as type-stable.
>   
>   When establishing the locking state for several lock types (including
>   blockable mutexes and sx) failed, locking primitives try to spin while
>   the owner thread is running.  The spinning loop performs the test for
>   running condition by dereferencing the owner->td_state field of the
>   owner thread.  If the owner thread exited while spinner was put off
>   the processor, it is harmless to access reused struct thread owner,
>   since in some near future the current processor would notice the owner
>   change and make appropriate progress.  But it could be that the page
>   which carried the freed struct thread was unmapped, then we fault
>   (this cannot happen on amd64).
>   
>   For now, disallowing free of the struct thread seems to be good
>   enough, and tests which create a lot of threads once, did not
>   demonstrated regressions.
>   
>   Reviewed by:	jhb, pho
>   Reported and tested by:	pho
>   Sponsored by:	The FreeBSD Foundation
>   MFC after:	2 weeks
>   Differential revision:	https://reviews.freebsd.org/D3908

PR:    65448

-- 
John Baldwin