pacemaker  2.0.4-2deceaa
Scalable High-Availability cluster resource manager
 All Data Structures Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
pid.c
Go to the documentation of this file.
1 /*
2  * Copyright 2004-2020 the Pacemaker project contributors
3  *
4  * The version control history for this file may have further details.
5  *
6  * This source code is licensed under the GNU Lesser General Public License
7  * version 2.1 or later (LGPLv2.1+) WITHOUT ANY WARRANTY.
8  */
9 
10 #include <crm_internal.h>
11 
12 #ifndef _GNU_SOURCE
13 # define _GNU_SOURCE
14 #endif
15 
16 #include <stdio.h>
17 #include <string.h>
18 #include <sys/stat.h>
19 
20 #include <crm/crm.h>
21 
22 int
23 pcmk__pid_active(pid_t pid, const char *daemon)
24 {
25  static pid_t last_asked_pid = 0; /* log spam prevention */
26 #if SUPPORT_PROCFS
27  static int have_proc_pid = 0;
28 #else
29  static int have_proc_pid = -1;
30 #endif
31  int rc = 0;
32  bool no_name_check = ((daemon == NULL) || (have_proc_pid == -1));
33 
34  if (have_proc_pid == 0) {
35  /* evaluation of /proc/PID/exe applicability via self-introspection */
36  char proc_path[PATH_MAX], exe_path[PATH_MAX];
37  snprintf(proc_path, sizeof(proc_path), "/proc/%lld/exe",
38  (long long) getpid());
39  have_proc_pid = 1;
40  if (readlink(proc_path, exe_path, sizeof(exe_path) - 1) < 0) {
41  have_proc_pid = -1;
42  }
43  }
44 
45  if (pid <= 0) {
46  return EINVAL;
47  }
48 
49  rc = kill(pid, 0);
50  if ((rc < 0) && (errno == ESRCH)) {
51  return ESRCH; /* no such PID detected */
52 
53  } else if ((rc < 0) && no_name_check) {
54  rc = errno;
55  if (last_asked_pid != pid) {
56  crm_info("Cannot examine PID %lld: %s",
57  (long long) pid, strerror(errno));
58  last_asked_pid = pid;
59  }
60  return rc; /* errno != ESRCH */
61 
62  } else if ((rc == 0) && no_name_check) {
63  return pcmk_rc_ok; /* kill as the only indicator, cannot double check */
64 
65  } else if (daemon != NULL) {
66  /* make sure PID hasn't been reused by another process
67  XXX: might still be just a zombie, which could confuse decisions */
68  bool checked_through_kill = (rc == 0);
69  char proc_path[PATH_MAX], exe_path[PATH_MAX], myexe_path[PATH_MAX];
70  snprintf(proc_path, sizeof(proc_path), "/proc/%lld/exe",
71  (long long) pid);
72 
73  rc = readlink(proc_path, exe_path, sizeof(exe_path) - 1);
74  if (rc < 0) {
75  if (last_asked_pid != pid) {
76  crm_err("Could not read from %s: %s " CRM_XS " errno=%d",
77  proc_path, strerror(errno), errno);
78  last_asked_pid = pid;
79  }
80  if ((errno == EACCES) && checked_through_kill) {
81  // Trust kill result, can't double-check via path
82  return pcmk_rc_ok;
83  } else if (errno == EACCES) {
84  return EACCES;
85  } else {
86  return ESRCH; /* most likely errno == ENOENT */
87  }
88  }
89  exe_path[rc] = '\0';
90 
91  if (daemon[0] != '/') {
92  rc = snprintf(myexe_path, sizeof(myexe_path), CRM_DAEMON_DIR"/%s",
93  daemon);
94  } else {
95  rc = snprintf(myexe_path, sizeof(myexe_path), "%s", daemon);
96  }
97 
98  if (rc > 0 && rc < sizeof(myexe_path) && !strcmp(exe_path, myexe_path)) {
99  return pcmk_rc_ok;
100  }
101  }
102 
103  return ESRCH;
104 }
105 
106 #define LOCKSTRLEN 11
107 
117 int
118 pcmk__read_pidfile(const char *filename, pid_t *pid)
119 {
120  int fd;
121  struct stat sbuf;
123  long long pid_read = 0;
124  char buf[LOCKSTRLEN + 1];
125 
126  CRM_CHECK((filename != NULL) && (pid != NULL), return EINVAL);
127 
128  fd = open(filename, O_RDONLY);
129  if (fd < 0) {
130  return errno;
131  }
132 
133  if ((fstat(fd, &sbuf) >= 0) && (sbuf.st_size < LOCKSTRLEN)) {
134  sleep(2); /* if someone was about to create one,
135  * give'm a sec to do so
136  */
137  }
138 
139  if (read(fd, buf, sizeof(buf)) < 1) {
140  rc = errno;
141  goto bail;
142  }
143 
144  if (sscanf(buf, "%lld", &pid_read) > 0) {
145  if (pid_read <= 0) {
146  rc = ESRCH;
147  } else {
148  rc = pcmk_rc_ok;
149  *pid = (pid_t) pid_read;
150  crm_trace("Read pid %lld from %s", pid_read, filename);
151  }
152  }
153 
154  bail:
155  close(fd);
156  return rc;
157 }
158 
171 int
172 pcmk__pidfile_matches(const char *filename, pid_t expected_pid,
173  const char *expected_name, pid_t *pid)
174 {
175  pid_t pidfile_pid = 0;
176  int rc = pcmk__read_pidfile(filename, &pidfile_pid);
177 
178  if (pid) {
179  *pid = pidfile_pid;
180  }
181 
182  if (rc != pcmk_rc_ok) {
183  // Error reading PID file or invalid contents
184  unlink(filename);
185  rc = ENOENT;
186 
187  } else if ((expected_pid > 0) && (pidfile_pid == expected_pid)) {
188  // PID in file matches what was expected
189  rc = pcmk_rc_ok;
190 
191  } else if (pcmk__pid_active(pidfile_pid, expected_name) == ESRCH) {
192  // Contains a stale value
193  unlink(filename);
194  rc = ENOENT;
195 
196  } else if ((expected_pid > 0) && (pidfile_pid != expected_pid)) {
197  // Locked by existing process
198  rc = EEXIST;
199  }
200 
201  return rc;
202 }
203 
213 int
214 pcmk__lock_pidfile(const char *filename, const char *name)
215 {
216  pid_t mypid = getpid();
217  int fd = 0;
218  int rc = 0;
219  char buf[LOCKSTRLEN + 2];
220 
221  rc = pcmk__pidfile_matches(filename, 0, name, NULL);
222  if ((rc != pcmk_rc_ok) && (rc != ENOENT)) {
223  // Locked by existing process
224  return rc;
225  }
226 
227  fd = open(filename, O_CREAT | O_WRONLY | O_EXCL, 0644);
228  if (fd < 0) {
229  return errno;
230  }
231 
232  snprintf(buf, sizeof(buf), "%*lld\n", LOCKSTRLEN - 1, (long long) mypid);
233  rc = write(fd, buf, LOCKSTRLEN);
234  close(fd);
235 
236  if (rc != LOCKSTRLEN) {
237  crm_perror(LOG_ERR, "Incomplete write to %s", filename);
238  return errno;
239  }
240 
241  rc = pcmk__pidfile_matches(filename, mypid, name, NULL);
242  if (rc != pcmk_rc_ok) {
243  // Something is really wrong -- maybe I/O error on read back?
244  unlink(filename);
245  }
246  return rc;
247 }
#define CRM_CHECK(expr, failure_action)
Definition: logging.h:233
A dumping ground.
int pcmk__read_pidfile(const char *filename, pid_t *pid)
Definition: pid.c:118
uint32_t pid
Definition: internal.h:81
char * strerror(int errnum)
int daemon(int nochdir, int noclose)
int rc
Definition: pcmk_fence.c:34
#define CRM_DAEMON_DIR
Definition: config.h:26
#define crm_trace(fmt, args...)
Definition: logging.h:369
int pcmk__pid_active(pid_t pid, const char *daemon)
Definition: pid.c:23
#define CRM_XS
Definition: logging.h:54
int pcmk__lock_pidfile(const char *filename, const char *name)
Definition: pid.c:214
#define crm_perror(level, fmt, args...)
Send a system error message to both the log and stderr.
Definition: logging.h:314
#define crm_err(fmt, args...)
Definition: logging.h:363
int pcmk__pidfile_matches(const char *filename, pid_t expected_pid, const char *expected_name, pid_t *pid)
Definition: pid.c:172
#define LOCKSTRLEN
Definition: pid.c:106
char * name
Definition: pcmk_fence.c:30
#define crm_info(fmt, args...)
Definition: logging.h:366