Update PGM interface with kernel

This patch updates the PGM interface with the kernel.
Producers now boost their priority when generating tokens,
not consumers while waiting for tokens.

1 files changed, 38 insertions, 17 deletions

diff --git a/src/kernel_iface.c b/src/kernel_iface.c
index 3fe4f60..1aa941d 100644
--- a/src/kernel_iface.c
+++ b/src/kernel_iface.c
@@ -2,7 +2,7 @@
 #include <sys/fcntl.h> /* for O_RDWR */
 #include <sys/unistd.h>
 #include <sched.h> /* for sched_yield() */
-
+#include <assert.h>
 
 #include <stdio.h>
 
@@ -144,10 +144,9 @@ int requested_to_preempt(void)
 void enter_pgm_wait(void)
 {
         if (likely(ctrl_page != NULL) || init_kernel_iface() == 0) {
-                if (!ctrl_page->pgm_waiting) {
-                        ctrl_page->pgm_waiting = 1;
-                        __sync_synchronize();
-                }
+                assert(!ctrl_page->pgm_waiting);
+                ctrl_page->pgm_waiting = 1;
+                __sync_synchronize();
         }
         else {
                 fprintf(stderr, "enter_pgm_wait: control page not mapped!\n");
@@ -157,22 +156,44 @@ void enter_pgm_wait(void)
 void exit_pgm_wait(void)
 {
         if (likely(ctrl_page != NULL)) {
-                if (ctrl_page->pgm_waiting) {
-                        ctrl_page->pgm_satisfied = 1;
-                        __sync_synchronize();
+                assert(ctrl_page->pgm_waiting);
+                ctrl_page->pgm_waiting = 0;
+                __sync_synchronize();
+        }
+        else {
+                fprintf(stderr, "exit_pgm_wait: control page not mapped!\n");
+        }
+}
 
-                        /* re-eval priority. Should clear pgm_waiting and pgm_satisfied */
-                        sched_yield();
+void enter_pgm_send(void)
+{
+        if (likely(ctrl_page != NULL) || init_kernel_iface() == 0) {
+                assert(!ctrl_page->pgm_sending);
+                ctrl_page->pgm_sending = 1; /* we will become boosted if
+                                               anyone tries to preempt us. */
+                __sync_synchronize();
+        }
+        else {
+                fprintf(stderr, "enter_pgm_send: control page not mapped!\n");
+        }
+}
 
-                        if (ctrl_page->pgm_waiting || ctrl_page->pgm_satisfied) {
-                                fprintf(stderr, "exit_pgm_wait: pgm flags not cleared! "
-                                        "waiting:%d satisfied:%d\n",
-                                        ctrl_page->pgm_waiting, ctrl_page->pgm_satisfied);
-                        }
-                }
+void exit_pgm_send(void)
+{
+        if (likely(ctrl_page != NULL)) {
+                assert(ctrl_page->pgm_sending);
+
+                ctrl_page->pgm_satisfied = 1;
+                __sync_synchronize();
+
+                /* re-eval priority. Should clear pgm_sending and pgm_satisfied. */
+                sched_yield();
+
+                /* double check that Litmus is doing its job */
+                assert(!ctrl_page->pgm_sending && !ctrl_page->pgm_satisfied);
         }
         else {
-                fprintf(stderr, "exit_pgm_wait: control page not mapped!\n");
+                fprintf(stderr, "exit_pgm_send: control page not mapped!\n");
         }
 }