lib/common/pid.c

/* */
This source file includes following definitions.
pcmk__pid_active
pcmk__read_pidfile
pcmk__pidfile_matches
pcmk__lock_pidfile
   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                 if (errno == EACCES) {
  77                     crm_info("Could not read from %s: %s " CRM_XS " errno=%d",
  78                              proc_path, strerror(errno), errno);
  79                 } else {
  80                     crm_err("Could not read from %s: %s " CRM_XS " errno=%d",
  81                             proc_path, strerror(errno), errno);
  82                 }
  83                 last_asked_pid = pid;
  84             }
  85             if ((errno == EACCES) && checked_through_kill) {
  86                 // Trust kill result, can't double-check via path
  87                 return pcmk_rc_ok;
  88             } else if (errno == EACCES) {
  89                 return EACCES;
  90             } else {
  91                 return ESRCH;  /* most likely errno == ENOENT */
  92             }
  93         }
  94         exe_path[rc] = '\0';
  95 
  96         if (daemon[0] != '/') {
  97             rc = snprintf(myexe_path, sizeof(myexe_path), CRM_DAEMON_DIR"/%s",
  98                           daemon);
  99         } else {
 100             rc = snprintf(myexe_path, sizeof(myexe_path), "%s", daemon);
 101         }
 102 
 103         if (rc > 0 && rc < sizeof(myexe_path) && !strcmp(exe_path, myexe_path)) {
 104             return pcmk_rc_ok;
 105         }
 106     }
 107 
 108     return ESRCH;
 109 }
 110 
 111 #define LOCKSTRLEN      11
 112 
 113 /*!
 114  * \internal
 115  * \brief Read a process ID from a file
 116  *
 117  * \param[in]  filename  Process ID file to read
 118  * \param[out] pid       Where to put PID that was read
 119  *
 120  * \return Standard Pacemaker return code
 121  */
 122 int
 123 pcmk__read_pidfile(const char *filename, pid_t *pid)
     /*  */
 124 {
 125     int fd;
 126     struct stat sbuf;
 127     int rc = pcmk_rc_unknown_format;
 128     long long pid_read = 0;
 129     char buf[LOCKSTRLEN + 1];
 130 
 131     CRM_CHECK((filename != NULL) && (pid != NULL), return EINVAL);
 132 
 133     fd = open(filename, O_RDONLY);
 134     if (fd < 0) {
 135         return errno;
 136     }
 137 
 138     if ((fstat(fd, &sbuf) >= 0) && (sbuf.st_size < LOCKSTRLEN)) {
 139         sleep(2);           /* if someone was about to create one,
 140                              * give'm a sec to do so
 141                              */
 142     }
 143 
 144     if (read(fd, buf, sizeof(buf)) < 1) {
 145         rc = errno;
 146         goto bail;
 147     }
 148 
 149     if (sscanf(buf, "%lld", &pid_read) > 0) {
 150         if (pid_read <= 0) {
 151             rc = ESRCH;
 152         } else {
 153             rc = pcmk_rc_ok;
 154             *pid = (pid_t) pid_read;
 155             crm_trace("Read pid %lld from %s", pid_read, filename);
 156         }
 157     }
 158 
 159   bail:
 160     close(fd);
 161     return rc;
 162 }
 163 
 164 /*!
 165  * \internal
 166  * \brief Check whether a process from a PID file matches expected values
 167  *
 168  * \param[in]  filename       Path of PID file
 169  * \param[in]  expected_pid   If positive, compare to this PID
 170  * \param[in]  expected_name  If not NULL, the PID from the PID file is valid
 171  *                            only if it is active as a process with this name
 172  * \param[out] pid            If not NULL, store PID found in PID file here
 173  *
 174  * \return Standard Pacemaker return code
 175  */
 176 int
 177 pcmk__pidfile_matches(const char *filename, pid_t expected_pid,
     /*  */
 178                       const char *expected_name, pid_t *pid)
 179 {
 180     pid_t pidfile_pid = 0;
 181     int rc = pcmk__read_pidfile(filename, &pidfile_pid);
 182 
 183     if (pid) {
 184         *pid = pidfile_pid;
 185     }
 186 
 187     if (rc != pcmk_rc_ok) {
 188         // Error reading PID file or invalid contents
 189         unlink(filename);
 190         rc = ENOENT;
 191 
 192     } else if ((expected_pid > 0) && (pidfile_pid == expected_pid)) {
 193         // PID in file matches what was expected
 194         rc = pcmk_rc_ok;
 195 
 196     } else if (pcmk__pid_active(pidfile_pid, expected_name) == ESRCH) {
 197         // Contains a stale value
 198         unlink(filename);
 199         rc = ENOENT;
 200 
 201     } else if ((expected_pid > 0) && (pidfile_pid != expected_pid)) {
 202         // Locked by existing process
 203         rc = EEXIST;
 204     }
 205 
 206     return rc;
 207 }
 208 
 209 /*!
 210  * \internal
 211  * \brief Create a PID file for the current process (if not already existent)
 212  *
 213  * \param[in] filename   Name of PID file to create
 214  * \param[in] name       Name of current process
 215  *
 216  * \return Standard Pacemaker return code
 217  */
 218 int
 219 pcmk__lock_pidfile(const char *filename, const char *name)
     /*  */
 220 {
 221     pid_t mypid = getpid();
 222     int fd = 0;
 223     int rc = 0;
 224     char buf[LOCKSTRLEN + 2];
 225 
 226     rc = pcmk__pidfile_matches(filename, 0, name, NULL);
 227     if ((rc != pcmk_rc_ok) && (rc != ENOENT)) {
 228         // Locked by existing process
 229         return rc;
 230     }
 231 
 232     fd = open(filename, O_CREAT | O_WRONLY | O_EXCL, 0644);
 233     if (fd < 0) {
 234         return errno;
 235     }
 236 
 237     snprintf(buf, sizeof(buf), "%*lld\n", LOCKSTRLEN - 1, (long long) mypid);
 238     rc = write(fd, buf, LOCKSTRLEN);
 239     close(fd);
 240 
 241     if (rc != LOCKSTRLEN) {
 242         crm_perror(LOG_ERR, "Incomplete write to %s", filename);
 243         return errno;
 244     }
 245 
 246     rc = pcmk__pidfile_matches(filename, mypid, name, NULL);
 247     if (rc != pcmk_rc_ok) {
 248         // Something is really wrong -- maybe I/O error on read back?
 249         unlink(filename);
 250     }
 251     return rc;
 252 }
/* */
root/lib/common/pid.c

DEFINITIONS
