The umtx_lock mutex is used by top-half of the kernel, but is

currently a spin lock.  Apparently, the only reason for this is that
umtx_thread_exit() is called under the process spinlock, which put the
requirement on the umtx_lock.  Note that the witness static order list
is wrong for the umtx_lock, umtx_lock is explicitely before any thread
lock, so it is also before sleepq locks.

Change umtx_lock to be the sleepable mutex.  For the reason above, the
calls to umtx_thread_exit() are moved from thread_exit() earlier in
each caller, when the process spin lock is not yet taken.

Discussed with:	jhb
Tested by:	pho (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	3 weeks

1 files changed, 1 insertions, 0 deletions

diff --git a/sys/kern/kern_thr.c b/sys/kern/kern_thr.c
index b298f33..280bc0b 100644
--- a/sys/kern/kern_thr.c
+++ b/sys/kern/kern_thr.c
@@ -322,6 +322,7 @@ sys_thr_exit(struct thread *td, struct thr_exit_args *uap)
 		LIST_REMOVE(td, td_hash);
 		rw_wunlock(&tidhash_lock);
 		tdsigcleanup(td);
+		umtx_thread_exit(td);
 		PROC_SLOCK(p);
 		thread_stopped(p);
 		thread_exit();