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Diffstat (limited to 'src')
| -rw-r--r-- | src/slack.c | 139 |
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; +} + |