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, 1 insertions, 3 deletions

diff --git a/sys/kern/kern_poll.c b/sys/kern/kern_poll.c
index 992116f..dadd7a3 100644
--- a/sys/kern/kern_poll.c
+++ b/sys/kern/kern_poll.c
@@ -577,13 +577,11 @@ poll_idle(void)
 {
 	struct thread *td = curthread;
 	struct rtprio rtp;
-	int pri;
 
 	rtp.prio = RTP_PRIO_MAX;	/* lowest priority */
 	rtp.type = RTP_PRIO_IDLE;
 	mtx_lock_spin(&sched_lock);
 	rtp_to_pri(&rtp, td->td_ksegrp);
-	pri = td->td_priority;
 	mtx_unlock_spin(&sched_lock);
 
 	for (;;) {
@@ -595,7 +593,7 @@ poll_idle(void)
 			mtx_unlock_spin(&sched_lock);
 		} else {
 			idlepoll_sleeping = 1;
-			tsleep(&idlepoll_sleeping, pri, "pollid", hz * 3);
+			tsleep(&idlepoll_sleeping, 0, "pollid", hz * 3);
 		}
 	}
 }