Change msleep() and tsleep() to not alter the calling thread's priority

if the specified priority is zero.  This avoids a race where the calling
thread could read a snapshot of it's current priority, then a different
thread could change the first thread's priority, then the original thread
would call sched_prio() inside msleep() undoing the change made by the
second thread.  I used a priority of zero as no thread that calls msleep()
or tsleep() should be specifying a priority of zero anyway.

The various places that passed 'curthread->td_priority' or some variant
as the priority now pass 0.

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/kern/kern_thr.c b/sys/kern/kern_thr.c
index f589160..d0f786e 100644
--- a/sys/kern/kern_thr.c
+++ b/sys/kern/kern_thr.c
@@ -368,8 +368,8 @@ thr_suspend(struct thread *td, struct thr_suspend_args *uap)
 	}
 	PROC_LOCK(td->td_proc);
 	if ((td->td_flags & TDF_THRWAKEUP) == 0)
-		error = msleep((void *)td, &td->td_proc->p_mtx,
-		    td->td_priority | PCATCH, "lthr", hz);
+		error = msleep((void *)td, &td->td_proc->p_mtx, PCATCH, "lthr",
+		    hz);
 	if (td->td_flags & TDF_THRWAKEUP) {
 		mtx_lock_spin(&sched_lock);
 		td->td_flags &= ~TDF_THRWAKEUP;