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, 8 deletions

diff --git a/sys/dev/hwpmc/hwpmc_mod.c b/sys/dev/hwpmc/hwpmc_mod.c
index 1ea0e68..579b6fd 100644
--- a/sys/dev/hwpmc/hwpmc_mod.c
+++ b/sys/dev/hwpmc/hwpmc_mod.c
@@ -646,15 +646,8 @@ pmc_select_cpu(int cpu)
 static void
 pmc_force_context_switch(void)
 {
-	u_char	curpri;
-
-	mtx_lock_spin(&sched_lock);
-	curpri = curthread->td_priority;
-	mtx_unlock_spin(&sched_lock);
-
-	(void) tsleep((void *) pmc_force_context_switch, curpri,
-	    "pmcctx", 1);
 
+	(void) tsleep((void *) pmc_force_context_switch, 0, "pmcctx", 1);
 }
 
 /*