Centralized Linux scheduler settings (beaglebone.h) and uniform implementation.

Author: modmaker

analog.c

@@ -195,7 +195,14 @@ int analog_init( void)
       pd->average.remainder = 0;
       ++num_analog_channels;
     }
-    return mendel_thread_create( "analog", &worker, NULL, &analog_worker, NULL);
+    if (mendel_thread_create( "analog", &worker, NULL, &analog_worker, NULL) != 0) {
+      return -1;
+    }
+    struct sched_param param = {
+      .sched_priority = ANALOG_PRIO
+    };
+    pthread_setschedparam( worker, ANALOG_SCHED, &param);
+    return 0;
   }
   fprintf( stderr, "analog_init: no configuration data!\n");
   return -1;

beaglebone.h

@@ -2,6 +2,37 @@
 #define _BEAGLEBONE_H
 
 #include <stdint.h>
+#include <sched.h>
+
+/*
+ * Posix defines priorities from 0 upto 99.
+ *  0 (lowest) is for SCHED_OTHER, the default scheduling algorithm
+ *  1 (low)    is for SCHED_RR and SCHED_FIFO
+ * 99 (high)   is for SCHED_RR and SCHED_FIFO
+ *
+ * The Linux kernel uses other values: Posix 0 gives Linux 120,
+ * Posix priority 1 gives Linux priority 98, Posix priority 99 gives Linux priority 0.
+ */
+
+#define TOP_PRIO	60
+#define ELEV_PRIO	55
+#define NORM_PRIO	50
+
+#define COMM_PRIO	TOP_PRIO	/* keep connection allive at all times */
+#define COMM_SCHED	SCHED_FIFO
+
+#define LIMSW_PRIO      TOP_PRIO
+#define LIMSW_SCHED	SCHED_FIFO
+
+#define MENDEL_PRIO	NORM_PRIO
+#define MENDEL_SCHED	SCHED_RR
+
+#define HEATER_PRIO	NORM_PRIO
+#define HEATER_SCHED	SCHED_RR
+
+#define ANALOG_PRIO	ELEV_PRIO
+#define ANALOG_SCHED	SCHED_RR
+
 
 #define NR_ITEMS( x) (sizeof( (x)) / sizeof( *(x)))
 

comm.c

@@ -165,15 +165,13 @@ int comm_init( void)
   alt_stdin = fds[ 1];
   fprintf( stderr, "alt_stdin = %d\n", alt_stdin);
 
-  result = mendel_thread_create( "comm", &worker, NULL, &comm_thread, NULL);
-  if (result != 0) {
-    exit( EXIT_FAILURE);
+  if (mendel_thread_create( "comm", &worker, NULL, &comm_thread, NULL) != 0) {
+    return -1;
   }
   struct sched_param param = {
-    .sched_priority = 74
+    .sched_priority = COMM_PRIO
   };
-  // SCHED_RR seems to work for now, otherwise use SCHED_FIFO
-  pthread_setschedparam( worker, SCHED_RR, &param);
+  pthread_setschedparam( worker, COMM_SCHED, &param);
 
   return 0;
 }

heater.c

@@ -203,7 +203,14 @@ int heater_init( void)
       ++num_heater_channels;
     }
     // Start worker thread
-    return mendel_thread_create( "heater", &worker, NULL, &heater_thread, NULL);
+    if (mendel_thread_create( "heater", &worker, NULL, &heater_thread, NULL) != 0) {
+      return -1;
+    }
+    struct sched_param param = {
+      .sched_priority = HEATER_PRIO
+    };
+    pthread_setschedparam( worker, HEATER_SCHED, &param);
+    return 0;
   }
   fprintf( stderr, "temp_init: no configuration data!\n");
   return -1;

limit_switches.c

@@ -159,19 +159,15 @@ static pthread_t worker;
 
 int limsw_init( void)
 {
-  int result;
-
   fdset = calloc( nr_limits, sizeof( struct pollfd));
 
-  result = mendel_thread_create( "limit_switches", &worker, NULL, &limsw_watcher, NULL);
-  if (result != 0) {
-    exit( EXIT_FAILURE);
+  if (mendel_thread_create( "limit_switches", &worker, NULL, &limsw_watcher, NULL) != 0) {
+    return -1;
   }
   struct sched_param param = {
-    .sched_priority = 74
+    .sched_priority = LIMSW_PRIO
   };
-  //  pthread_setschedparam( worker, SCHED_FIFO, &param);
-  pthread_setschedparam( worker, SCHED_RR, &param);
+  pthread_setschedparam( worker, LIMSW_SCHED, &param);
 
   return 0;
 }

mendel.c

@@ -6,7 +6,6 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <time.h>
-#include <sched.h>
 #include <pthread.h>
 #include <signal.h>
 
@@ -29,18 +28,18 @@ static int arm_init( void)
     exit( EXIT_FAILURE);
   }
 
-  int policy = SCHED_OTHER;
+  int policy = MENDEL_SCHED;
   int prio_max = sched_get_priority_max( policy);
   int prio_min = sched_get_priority_min( policy);
 
   struct sched_param sp = { 
-    .sched_priority = (prio_min + prio_max) / 2
+    .sched_priority = MENDEL_PRIO
   };
   // Set realtime process scheduling using the Round Robin scheduler
   // with absolute priority halfway between min and max.
   if (sched_setscheduler( 0, policy, &sp) < 0) {
   }
-  fprintf( stderr, "Scheduler set to %d, priority to %d\n", policy, sp.sched_priority);
+  fprintf( stderr, "Scheduler set to %d, priority to %d (min:%d,max:%d)\n", policy, sp.sched_priority, prio_min, prio_max);
 
   struct timespec clock_resolution;
   clock_getres( CLOCK_MONOTONIC, &clock_resolution);