Re-implement non-preemptive section support.

Re-introduce NP sections in the configuration and in litmus.h. Remove the old
np_flag from rt_param.

If CONFIG_NP_SECTION is disabled, then all non-preemptive section checks are
constant expressions which should get removed by the dead code elimination
during optimization.

Instead of re-implementing sys_exit_np(), we simply repurposed sched_yield()
for calling into the scheduler to trigger delayed preemptions.

1 files changed, 7 insertions, 20 deletions

diff --git a/include/litmus/rt_param.h b/include/litmus/rt_param.h
index 9353251fb30e..5b94d1a8eea7 100644
--- a/include/litmus/rt_param.h
+++ b/include/litmus/rt_param.h
@@ -85,7 +85,6 @@ struct rt_job {
         unsigned int    job_no;
 };
 
-
 struct pfair_param;
 
 /*      RT task parameters for scheduling extensions
@@ -116,26 +115,14 @@ struct rt_param {
          */
          struct task_struct*    inh_task;
 
-        /* Don't just dereference this pointer in kernel space!
-         * It might very well point to junk or nothing at all.
-         * NULL indicates that the task has not requested any non-preemptable
-         * section support.
-         * Not inherited upon fork.
+#ifdef CONFIG_NP_SECTION
+        /* For the FMLP under PSN-EDF, it is required to make the task
+         * non-preemptive from kernel space. In order not to interfere with
+         * user space, this counter indicates the kernel space np setting.
+         * kernel_np > 0 => task is non-preemptive
          */
-        short*                  np_flag;
-
-        /* re-use unused counter in plugins that don't need it */
-        union {
-                /* For the FMLP under PSN-EDF, it is required to make the task
-                 * non-preemptive from kernel space. In order not to interfere with
-                 * user space, this counter indicates the kernel space np setting.
-                 * kernel_np > 0 => task is non-preemptive
-                 */
-                unsigned int    kernel_np;
-
-                /* Used by GQ-EDF */
-                unsigned int    last_cpu;
-        };
+        unsigned int    kernel_np;
+#endif
 
         /* This field can be used by plugins to store where the task
          * is currently scheduled. It is the responsibility of the