Eric Lee / smarc-fsl-linux-kernel

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Documentation/cgroups/cgroup_event_listener.c 2.13 KB
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1d8fd973a   Kirill A. Shutemov   cgroups: add simp... 
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  /*
   * cgroup_event_listener.c - Simple listener of cgroup events
   *
   * Copyright (C) Kirill A. Shutemov <kirill@shutemov.name>
   */
  
  #include <assert.h>
  #include <errno.h>
  #include <fcntl.h>
  #include <libgen.h>
  #include <limits.h>
  #include <stdio.h>
  #include <string.h>
  #include <unistd.h>
  
  #include <sys/eventfd.h>
  
  #define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>
  "
  
  int main(int argc, char **argv)
  {
  	int efd = -1;
  	int cfd = -1;
  	int event_control = -1;
  	char event_control_path[PATH_MAX];
  	char line[LINE_MAX];
  	int ret;
  
  	if (argc != 3) {
  		fputs(USAGE_STR, stderr);
  		return 1;
  	}
  
  	cfd = open(argv[1], O_RDONLY);
  	if (cfd == -1) {
  		fprintf(stderr, "Cannot open %s: %s
  ", argv[1],
  				strerror(errno));
  		goto out;
  	}
  
  	ret = snprintf(event_control_path, PATH_MAX, "%s/cgroup.event_control",
  			dirname(argv[1]));
  	if (ret >= PATH_MAX) {
  		fputs("Path to cgroup.event_control is too long
  ", stderr);
  		goto out;
  	}
  
  	event_control = open(event_control_path, O_WRONLY);
  	if (event_control == -1) {
  		fprintf(stderr, "Cannot open %s: %s
  ", event_control_path,
  				strerror(errno));
  		goto out;
  	}
  
  	efd = eventfd(0, 0);
  	if (efd == -1) {
  		perror("eventfd() failed");
  		goto out;
  	}
  
  	ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]);
  	if (ret >= LINE_MAX) {
  		fputs("Arguments string is too long
  ", stderr);
  		goto out;
  	}
  
  	ret = write(event_control, line, strlen(line) + 1);
  	if (ret == -1) {
  		perror("Cannot write to cgroup.event_control");
  		goto out;
  	}
  
  	while (1) {
  		uint64_t result;
  
  		ret = read(efd, &result, sizeof(result));
  		if (ret == -1) {
  			if (errno == EINTR)
  				continue;
  			perror("Cannot read from eventfd");
  			break;
  		}
  		assert(ret == sizeof(result));
  
  		ret = access(event_control_path, W_OK);
  		if ((ret == -1) && (errno == ENOENT)) {
  				puts("The cgroup seems to have removed.");
  				ret = 0;
  				break;
  		}
  
  		if (ret == -1) {
  			perror("cgroup.event_control "
b595076a1   Uwe Kleine-König   tree-wide: fix co... 
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  					"is not accessible any more");
1d8fd973a   Kirill A. Shutemov   cgroups: add simp... 
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  			break;
  		}
  
  		printf("%s %s: crossed
  ", argv[1], argv[2]);
  	}
  
  out:
  	if (efd >= 0)
  		close(efd);
  	if (event_control >= 0)
  		close(event_control);
  	if (cfd >= 0)
  		close(cfd);
  
  	return (ret != 0);
  }