Augment rt_task() with is_realtime()

Whenever the kernel checks for rt_task() to avoid delaying real-time
tasks, we want it to also not delay LITMUS^RT tasks.  Hence, most
calls to rt_task() should be matched by an equivalent call to
is_realtime().

Notably, this affects the implementations of select() and nanosleep(),
which use timer_slack_ns when setting up timers for non-real-time
tasks.

2 files changed, 6 insertions, 2 deletions

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 4cccea6b8934..a8546e29671e 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -27,6 +27,8 @@
 #include <linux/debug_locks.h>
 #include <linux/osq_lock.h>
 
+#include <litmus/litmus.h> /* for is_realtime() */
+
 /*
  * In the DEBUG case we are using the "NULL fastpath" for mutexes,
  * which forces all calls into the slowpath:
@@ -368,7 +370,7 @@ static bool mutex_optimistic_spin(struct mutex *lock,
                  * we're an RT task that will live-lock because we won't let
                  * the owner complete.
                  */
-                if (!owner && (need_resched() || rt_task(task)))
+                if (!owner && (need_resched() || rt_task(task) || is_realtime(task)))
                         break;
 
                 /*
diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index 3417d0172a5d..873ffca2321c 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -18,6 +18,8 @@
 
 #include "rwsem.h"
 
+#include <litmus/litmus.h> /* for is_realtime() */
+
 /*
  * Guide to the rw_semaphore's count field for common values.
  * (32-bit case illustrated, similar for 64-bit)
@@ -392,7 +394,7 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem)
                  * we're an RT task that will live-lock because we won't let
                  * the owner complete.
                  */
-                if (!owner && (need_resched() || rt_task(current)))
+                if (!owner && (need_resched() || rt_task(current) || is_realtime(current)))
                         break;
 
                 /*