EDF-WM: handle race between wake_up() and schedule()

A job that temporarily blocked without being descheduled
might have its slices advanced to the next CPU. In this case,
we need to force a rescheduling + migration.

1 files changed, 16 insertions, 2 deletions

diff --git a/litmus/sched_edf_wm.c b/litmus/sched_edf_wm.c
index c3d241a42566..baf03f7ca6ac 100644
--- a/litmus/sched_edf_wm.c
+++ b/litmus/sched_edf_wm.c
@@ -323,8 +323,7 @@ static struct task_struct* wm_schedule(struct task_struct * prev)
         rt_domain_t             *edf = &dom->domain;
         struct task_struct      *next, *migrate = NULL;
 
-        int                     out_of_time, sleep, preempt,
-                                exists, blocks, resched;
+        int out_of_time, sleep, preempt, wrong_cpu, exists, blocks, resched;
 
         raw_spin_lock(&dom->slock);
 
@@ -336,6 +335,7 @@ static struct task_struct* wm_schedule(struct task_struct * prev)
 
         /* (0) Determine state */
         exists      = dom->scheduled != NULL;
+        wrong_cpu   = exists && get_partition(dom->scheduled) != dom->cpu;
         blocks      = exists && !is_running(dom->scheduled);
         out_of_time = exists
                 && budget_enforced(dom->scheduled)
@@ -349,11 +349,25 @@ static struct task_struct* wm_schedule(struct task_struct * prev)
          */
         resched = preempt;
 
+
+        if (exists)
+                TRACE_TASK(prev,
+                           "blocks:%d out_of_time:%d sleep:%d preempt:%d "
+                           "wrong_cpu:%d state:%d sig:%d\n",
+                           blocks, out_of_time, sleep, preempt, wrong_cpu,
+                           prev->state, signal_pending(prev));
+
         /* If a task blocks we have no choice but to reschedule.
          */
         if (blocks)
                 resched = 1;
 
+        /* This can happen if sliced task was moved to the next slice
+         * by the wake_up() code path while still being scheduled.
+         */
+        if (wrong_cpu)
+                resched = 1;
+
         /* Any task that is preemptable and either exhausts its execution
          * budget or wants to sleep completes. We may have to reschedule after
          * this.