Upstream | cc2ee17 | 1970-01-12 13:46:40 +0000 | [diff] [blame] | 1 | /** |
| 2 | * @file op_lockfile.c |
| 3 | * PID-based lockfile management |
| 4 | * |
| 5 | * @remark Copyright 2002 OProfile authors |
| 6 | * @remark Read the file COPYING |
| 7 | * |
| 8 | * @author John Levon |
| 9 | * @author Philippe Elie |
| 10 | */ |
| 11 | |
| 12 | #include "op_lockfile.h" |
| 13 | #include "op_file.h" |
| 14 | |
| 15 | #include <errno.h> |
| 16 | |
| 17 | #include <sys/types.h> |
| 18 | #include <stdio.h> |
| 19 | #include <signal.h> |
| 20 | #include <unistd.h> |
| 21 | |
| 22 | static pid_t op_read_lock_file(char const * file) |
| 23 | { |
| 24 | FILE * fp; |
| 25 | pid_t value; |
| 26 | |
| 27 | fp = fopen(file, "r"); |
| 28 | if (fp == NULL) |
| 29 | return 0; |
| 30 | |
| 31 | if (fscanf(fp, "%d", &value) != 1) { |
| 32 | fclose(fp); |
| 33 | return 0; |
| 34 | } |
| 35 | |
| 36 | fclose(fp); |
| 37 | |
| 38 | return value; |
| 39 | } |
| 40 | |
| 41 | |
| 42 | int op_write_lock_file(char const * file) |
| 43 | { |
| 44 | FILE * fp; |
| 45 | |
| 46 | if (op_file_readable(file)) { |
| 47 | pid_t pid = op_read_lock_file(file); |
| 48 | |
| 49 | /* FIXME: ESRCH vs. EPERM */ |
| 50 | if (kill(pid, 0)) { |
| 51 | int err = unlink(file); |
| 52 | fprintf(stderr, "Removing stale lock file %s\n", |
| 53 | file); |
| 54 | if (err) |
| 55 | return err; |
| 56 | } else { |
| 57 | return EEXIST; |
| 58 | } |
| 59 | } |
| 60 | |
| 61 | fp = fopen(file, "w"); |
| 62 | if (!fp) |
| 63 | return errno; |
| 64 | |
| 65 | fprintf(fp, "%d", getpid()); |
| 66 | fclose(fp); |
| 67 | |
| 68 | return 0; |
| 69 | } |