From 6ec2bbce01c4d4287504d4d6b1df7c4d3870abce Mon Sep 17 00:00:00 2001
From: Glenn Elliott <gelliott@cs.unc.edu>
Date: Tue, 19 Nov 2013 14:10:33 -0500
Subject: 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.
---
 Makefile           |  2 +-
 include/litmus.h   |  2 ++
 src/kernel_iface.c | 55 +++++++++++++++++++++++++++++++++++++-----------------
 3 files changed, 41 insertions(+), 18 deletions(-)

diff --git a/Makefile b/Makefile
index e8003e8..39a79a7 100644
--- a/Makefile
+++ b/Makefile
@@ -19,7 +19,7 @@ LITMUS_KERNEL ?= ../litmus-rt
 # Internal configuration.
 
 # compiler flags
-flags-debug    = -O2 -Wall -Werror -g -Wdeclaration-after-statement
+flags-debug    = -Os -march=native -Wall -Werror -Wdeclaration-after-statement
 flags-api      = -D_XOPEN_SOURCE=600 -D_GNU_SOURCE
 
 # architecture-specific flags
diff --git a/include/litmus.h b/include/litmus.h
index 2817373..0f4566a 100644
--- a/include/litmus.h
+++ b/include/litmus.h
@@ -126,6 +126,8 @@ int  requested_to_preempt(void);
 /* pgm support */
 void enter_pgm_wait(void);
 void exit_pgm_wait(void);
+void enter_pgm_send(void);
+void exit_pgm_send(void);
 
 /* task system support */
 int wait_for_ts_release(void);
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");
 	}
 }
 
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