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, 8 insertions, 3 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 73cbc5dc150b..1f0073b95d17 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -38,6 +38,8 @@
 #include <linux/sched/rt.h>
 #include <trace/events/writeback.h>
 
+#include <litmus/litmus.h> /* for is_realtime() */
+
 /*
  * Sleep at most 200ms at a time in balance_dirty_pages().
  */
@@ -300,7 +302,7 @@ void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
         if (background >= dirty)
                 background = dirty / 2;
         tsk = current;
-        if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
+        if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk) || is_realtime(tsk)) {
                 background += background / 4;
                 dirty += dirty / 4;
         }
@@ -328,7 +330,7 @@ static unsigned long zone_dirty_limit(struct zone *zone)
         else
                 dirty = vm_dirty_ratio * zone_memory / 100;
 
-        if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk))
+        if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk) || is_realtime(tsk))
                 dirty += dirty / 4;
 
         return dirty;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2ee0fd313f03..65299391e760 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -61,6 +61,8 @@
 #include <linux/hugetlb.h>
 #include <linux/sched/rt.h>
 
+#include <litmus/litmus.h> /* for is_realtime() */
+
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
 #include "internal.h"
@@ -2362,7 +2364,8 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
                  * See also cpuset_zone_allowed() comment in kernel/cpuset.c.
                  */
                 alloc_flags &= ~ALLOC_CPUSET;
-        } else if (unlikely(rt_task(current)) && !in_interrupt())
+        } else if (unlikely(rt_task(current) || is_realtime(current))
+                   && !in_interrupt())
                 alloc_flags |= ALLOC_HARDER;
 
         if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {