first commit

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 139 insertions, 0 deletions

diff --git a/src/slack.c b/src/slack.c
new file mode 100644
index 0000000..bd9e6b1
--- /dev/null
+++ b/src/slack.c
@@ -0,0 +1,139 @@
+/**
+ * slack — Spawn processes with customised timer slack
+ * Copyright © 2014  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/prctl.h>
+
+
+static void usage(void)
+{
+  printf("USAGE: slack (get | GET | (reset | <interval> <options..> [--fatal] [--] <command..>))\n");
+  printf("\n");
+  printf("The <interval> must be a positive number optionally with a suffix:\n");
+  printf("  ns  n           nanoseconds (default)\n");
+  printf("  µs  µ  ns  n    microseconds\n");
+  printf("  ms  m           milliseconds\n");
+  printf("  s               seconds\n");
+  printf("\n");
+  printf("If `GET' is used rather than `get', the timer slack value will be printed in\n");
+  printf("nanoseconds without suffix. `GET' and `get' prints the current timer slack\n");
+  printf("value and exits.\n");
+  printf("\n");
+  printf("`reset` reset the timer slack value to the default (the time slack value for\n");
+  printf("the init process (PID 1) has.)\n");
+  printf("\n");
+  printf("Unless `--fatal` is used, the program will run <command> even if the timer\n");
+  printf("slack could not be set.\n");
+  printf("\n");
+}
+
+
+
+#define NS  (1L)
+#define US  (1000L)
+#define MS  (1000L * 1000L)
+#define S   (1000L * 1000L * 1000L)
+
+
+
+int main(int argc, char** argv)
+{
+  long slackvalue, r;
+  int i, j, fatal = 0;
+  char** exec_argv;
+  
+  if ((argc < 2) || !strcmp(argv[1], "--help") || !strcmp(argv[1], "help"))
+    return usage(), argc < 2 ? 1 : 0;
+  
+  if (!strcmp(argv[1], "get") || !strcmp(argv[1], "GET"))
+    {
+      const char* suffix;
+      if (r = prctl(PR_GET_TIMERSLACK), r < 0)
+	perror(*argv);
+      else
+	{
+	  if (!strcmp(argv[1], "GET"))
+	    suffix = "";
+	  else if (r %  S == 0)  suffix =  "s", r /=  S;
+	  else if (r % MS == 0)  suffix = "ms", r /= MS;
+	  else if (r % US == 0)  suffix = "µs", r /= US;
+	  else                   suffix = "ns";
+	  printf("%li%s\n", r, suffix);
+	}
+      return r > 0 ? 0 : 1;
+    }
+  
+  for (i = 2; i < argc; i++)
+    if (!strcmp(argv[i], "--fatal"))
+      fatal = 1;
+    else if (!strcmp(argv[i], "--"))
+      {
+	i++;
+	break;
+      }
+    else if (strstr(argv[i], "-") == argv[i])
+      return usage(), 1;
+    else
+      break;
+  
+  if (i == argc)
+    return usage(), 1;
+  
+  exec_argv = malloc((argc - i + 1) * sizeof(char*));
+  if (exec_argv == NULL)
+    return perror(*argv), 2;
+  exec_argv[argc - i] = NULL;
+  for (j = 0; i < argc; j++, i++)
+    exec_argv[j] = argv[i];
+  
+  if (!strcmp(argv[1], "reset"))
+    slackvalue = 0;
+  else
+    {
+      char* end;
+      
+      slackvalue = strtol(argv[1], &end, 10);
+      if (end == argv[1])
+	return fprintf(stderr, "No slack value specified."), 1;
+      
+      if      (!strcmp(end, "n") || !strcmp(end, "ns") || !strcmp(end, ""))  slackvalue *= NS;
+      else if (!strcmp(end, "µ") || !strcmp(end, "µs"))                      slackvalue *= US;
+      else if (!strcmp(end, "u") || !strcmp(end, "us"))                      slackvalue *= US;
+      else if (!strcmp(end, "m") || !strcmp(end, "ms"))                      slackvalue *= MS;
+      else if (!strcmp(end, "s"))                                            slackvalue *=  S;
+      else
+	return fprintf(stderr, "Unrecognised suffix for slack value."), 1;
+      
+      if (slackvalue <= 0)
+	return fprintf(stderr, "Invalid slack value: %lins", slackvalue), 1;
+    }
+  
+  if (r = prctl(PR_SET_TIMERSLACK, slackvalue), r < 0)
+    if (perror(*argv), fatal)
+      return 2;
+  
+  execvp(*exec_argv, exec_argv);
+  perror(*argv);
+  return 2;
+}
+