rt domain: evil hack to avoid recursive hrtimer lock acquisition

This is a really dirty hack, but works for now since our real-time
tasks do not use hrtimer_wakeup().

The need for this will go away when we port since newer versions of the
Linux kernel allow timers to be activated directly in the scheduler.

2 files changed, 28 insertions, 4 deletions

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 2bd9fc2a59..7b8576b6bd 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1314,6 +1314,9 @@ void hrtimer_run_queues(void)
                 run_hrtimer_queue(cpu_base, i);
 }
 
+/* FIXME: this won't be needed anymore once we port to Linux > 2.6.24 */
+void hrtimer_wakeup_hack(int onoff);
+
 /*
  * Sleep related functions:
  */
@@ -1324,8 +1327,11 @@ static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer)
         struct task_struct *task = t->task;
 
         t->task = NULL;
-        if (task)
+        if (task) {
+                hrtimer_wakeup_hack(1);
                 wake_up_process(task);
+                hrtimer_wakeup_hack(0);
+        }
 
         return HRTIMER_NORESTART;
 }
diff --git a/litmus/norqlock.c b/litmus/norqlock.c
index 769240075a..b812f34960 100644
--- a/litmus/norqlock.c
+++ b/litmus/norqlock.c
@@ -8,9 +8,10 @@
 
 struct worklist {
         struct no_rqlock_work* next;
+        int hrtimer_hack;
 };
 
-static DEFINE_PER_CPU(struct worklist, norq_worklist) = {NULL};
+static DEFINE_PER_CPU(struct worklist, norq_worklist) = {NULL, 0};
 
 void init_no_rqlock_work(struct no_rqlock_work* w, work_t work,
                          unsigned long arg)
@@ -33,15 +34,32 @@ void __do_without_rqlock(struct no_rqlock_work *work)
         local_irq_restore(flags);
 }
 
+void hrtimer_wakeup_hack(int onoff)
+{
+        preempt_disable();
+        __get_cpu_var(norq_worklist).hrtimer_hack = onoff;
+        preempt_enable();
+}
+
 void tick_no_rqlock(void)
 {
         long flags;
         struct no_rqlock_work *todo, *next;
+        struct worklist* wl;
+
 
         local_irq_save(flags);
 
-        next = __get_cpu_var(norq_worklist).next;
-        __get_cpu_var(norq_worklist).next = NULL;
+        wl = &__get_cpu_var(norq_worklist); 
+
+        if (wl->hrtimer_hack) {
+                /* bail out! */
+                local_irq_restore(flags);
+                return;
+        }
+
+        next = wl->next;
+        wl->next = NULL;
 
         local_irq_restore(flags);