Merge branch 't/ipc'
authorAndre Noll <maan@systemlinux.org>
Fri, 10 Aug 2012 11:49:54 +0000 (13:49 +0200)
committerAndre Noll <maan@systemlinux.org>
Fri, 10 Aug 2012 11:49:54 +0000 (13:49 +0200)
4d9f41 mutex_get(): Change parameter from key_t to int.
55c90e Implement --reload.
492928 Add the --kill subcommand.
dd42f7 Use semaphore locking to avoid starting dss multiple times.
17eea8 Introduce get_config_file_name().

That topic was cooking in next for a quite some time now.

Makefile
dss.c
dss.ggo
error.h
ipc.c [new file with mode: 0644]
ipc.h [new file with mode: 0644]

index 99b8286..25d6ea9 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-dss_objects := cmdline.o dss.o string.o fd.o exec.o signal.o daemon.o df.o time.o snap.o
+dss_objects := cmdline.o dss.o string.o fd.o exec.o signal.o daemon.o df.o time.o snap.o ipc.o
 all: dss
 man: dss.1
 
diff --git a/dss.c b/dss.c
index 968ba59..631b36d 100644 (file)
--- a/dss.c
+++ b/dss.c
@@ -33,6 +33,7 @@
 #include "df.h"
 #include "time.h"
 #include "snap.h"
+#include "ipc.h"
 
 /** Command line and config file options. */
 static struct gengetopt_args_info conf;
@@ -170,7 +171,10 @@ static void dump_dss_config(const char *msg)
        COMMAND(ls) \
        COMMAND(create) \
        COMMAND(prune) \
-       COMMAND(run)
+       COMMAND(run) \
+       COMMAND(kill) \
+       COMMAND(reload) \
+
 #define COMMAND(x) static int com_ ##x(void);
 COMMANDS
 #undef COMMAND
@@ -226,6 +230,47 @@ static __printf_1_2 void dss_msg(const char* fmt,...)
        va_end(argp);
 }
 
+static char *get_config_file_name(void)
+{
+       char *home, *config_file;
+
+       if (conf.config_file_given)
+               return dss_strdup(conf.config_file_arg);
+       home = get_homedir();
+       config_file = make_message("%s/.dssrc", home);
+       free(home);
+       return config_file;
+}
+
+static int send_signal(int sig)
+{
+       pid_t pid;
+       char *config_file = get_config_file_name();
+       int ret = get_dss_pid(config_file, &pid);
+
+       free(config_file);
+       if (ret < 0)
+               return ret;
+       if (conf.dry_run_given) {
+               dss_msg("%d\n", (int)pid);
+               return 0;
+       }
+       ret = kill(pid, sig);
+       if (ret < 0)
+               return -ERRNO_TO_DSS_ERROR(errno);
+       return 1;
+}
+
+static int com_kill(void)
+{
+       return send_signal(SIGTERM);
+}
+
+static int com_reload(void)
+{
+       return send_signal(SIGHUP);
+}
+
 static void dss_get_snapshot_list(struct snapshot_list *sl)
 {
        get_snapshot_list(sl, conf.unit_interval_arg, conf.num_intervals_arg);
@@ -883,18 +928,11 @@ static int check_config(void)
 static int parse_config_file(int override)
 {
        int ret, config_file_exists;
-       char *config_file;
+       char *config_file = get_config_file_name();
        struct stat statbuf;
        char *old_logfile_arg = NULL;
        int old_daemon_given = 0;
 
-       if (conf.config_file_given)
-               config_file = dss_strdup(conf.config_file_arg);
-       else {
-               char *home = get_homedir();
-               config_file = make_message("%s/.dssrc", home);
-               free(home);
-       }
        if (override) { /* SIGHUP */
                if (conf.logfile_given)
                        old_logfile_arg = dss_strdup(conf.logfile_arg);
@@ -1222,10 +1260,23 @@ static void exit_hook(int exit_code)
        dss_exec(&pid, conf.exit_hook_arg, argv);
 }
 
+static void lock_dss_or_die(void)
+{
+       char *config_file = get_config_file_name();
+       int ret = lock_dss(config_file);
+
+       free(config_file);
+       if (ret < 0) {
+               DSS_EMERG_LOG("failed to lock: %s\n", dss_strerror(-ret));
+               exit(EXIT_FAILURE);
+       }
+}
+
 static int com_run(void)
 {
        int ret;
 
+       lock_dss_or_die();
        if (conf.dry_run_given) {
                DSS_ERROR_LOG("dry_run not supported by this command\n");
                return -E_SYNTAX;
@@ -1248,6 +1299,7 @@ static int com_prune(void)
        struct disk_space ds;
        const char *why;
 
+       lock_dss_or_die();
        ret = get_disk_space(".", &ds);
        if (ret < 0)
                return ret;
@@ -1303,6 +1355,7 @@ static int com_create(void)
        int ret, status;
        char **rsync_argv;
 
+       lock_dss_or_die();
        if (conf.dry_run_given) {
                int i;
                char *msg = NULL;
diff --git a/dss.ggo b/dss.ggo
index 1662e0d..38e8637 100644 (file)
--- a/dss.ggo
+++ b/dss.ggo
@@ -145,6 +145,25 @@ details="
        received. See also the --exit-hook option.
 "
 
+groupoption "kill" K
+#~~~~~~~~~~~~~~~~~~~
+"Kill a running dss process"
+group="command"
+details="
+       This sends SIGTERM to the dss process that corresponds to the
+       given config file. If --dry-run is given, the PID of the dss
+       process is written to stdout, but no signal is sent.
+"
+
+groupoption "reload" -
+#~~~~~~~~~~~~~~~~~~~~~
+"force a running dss process to reload its config file"
+group="command"
+details="
+       This differs from --kill only in that SIGHUP rather than SIGTERM
+       is sent to the dss process.
+"
+
 ###############################
 section "Rsync-related options"
 ###############################
diff --git a/error.h b/error.h
index ade1a8e..2b62611 100644 (file)
--- a/error.h
+++ b/error.h
@@ -54,6 +54,7 @@ static inline char *dss_strerror(int num)
        DSS_ERROR(SIGNAL_SIG_ERR, "signal() returned SIG_ERR") \
        DSS_ERROR(SIGNAL, "caught terminating signal") \
        DSS_ERROR(BUG, "values of beta might cause dom!") \
+       DSS_ERROR(NOT_RUNNING, "dss not running") \
 
 
 /**
diff --git a/ipc.c b/ipc.c
new file mode 100644 (file)
index 0000000..c438939
--- /dev/null
+++ b/ipc.c
@@ -0,0 +1,365 @@
+#include <sys/wait.h>
+#include <stdio.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/sem.h>
+#include <string.h>
+#include <assert.h>
+#include <sys/stat.h>
+#include <stddef.h>
+#include <limits.h>
+#include <sys/param.h>
+
+#include "gcc-compat.h"
+#include "string.h"
+#include "log.h"
+#include "gcc-compat.h"
+#include "error.h"
+
+#if (defined(__GNUC__) && defined(__i386__))
+#define get16bits(d) (*((const uint16_t *) (d)))
+#else
+#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
+               +(uint32_t)(((const uint8_t *)(d))[0]) )
+#endif
+
+/*
+ * SuperFastHash, by Paul Hsieh.
+ * http://www.azillionmonkeys.com/qed/hash.html
+ */
+static uint32_t super_fast_hash(const uint8_t *data, uint32_t len, uint32_t hash)
+{
+       uint32_t tmp;
+       int rem = len & 3;
+
+       len >>= 2;
+
+       for (;len > 0; len--) {
+               hash  += get16bits (data);
+               tmp    = (get16bits (data+2) << 11) ^ hash;
+               hash   = (hash << 16) ^ tmp;
+               data  += 2*sizeof (uint16_t);
+               hash  += hash >> 11;
+       }
+
+       /* Handle end cases */
+       switch (rem) {
+       case 3:
+               hash += get16bits (data);
+               hash ^= hash << 16;
+               hash ^= data[sizeof (uint16_t)] << 18;
+               hash += hash >> 11;
+               break;
+       case 2:
+               hash += get16bits (data);
+               hash ^= hash << 11;
+               hash += hash >> 17;
+               break;
+       case 1:
+               hash += *data;
+               hash ^= hash << 10;
+               hash += hash >> 1;
+       }
+       /* Force "avalanching" of final 127 bits */
+       hash ^= hash << 3;
+       hash += hash >> 5;
+       hash ^= hash << 4;
+       hash += hash >> 17;
+       hash ^= hash << 25;
+       hash += hash >> 6;
+       return hash;
+}
+
+/*
+ * Return the canonical absolute name of a given file name.
+ *
+ * Slightly modified version of glibc's realpath, Copyright (C)
+ * 1996-2002,2004,2005,2006,2008 Free Software Foundation, Inc.
+ *
+ * A canonical name does not contain any `.', `..' components nor any repeated
+ * path separators ('/') or symlinks. All path components must exist. The
+ * result is malloc'd and must be freed by the caller.
+ */
+static int dss_realpath(const char *name, char **resolved_path)
+{
+       char *rpath = NULL, *dest, *extra_buf = NULL;
+       const char *start, *end, *rpath_limit;
+       long int path_max;
+       int ret, num_links = 0;
+
+       if (name[0] == '\0') {
+               /*
+                * As per Single Unix Specification V2 we must return an error
+                * if the name argument points to an empty string.
+                */
+               ret = -ERRNO_TO_DSS_ERROR(ENOENT);
+               goto error;
+       }
+#ifdef PATH_MAX
+       path_max = PATH_MAX;
+#else
+       /*
+        * From realpath(3): Asking pathconf(3) does not really help, since on
+        * the one hand POSIX warns that the result of pathconf(3) may be
+        * huge and unsuitable for mallocing memory. And on the other hand
+        * pathconf(3) may return -1 to signify that PATH_MAX is not bounded.
+        */
+       path_max = pathconf(name, _PC_PATH_MAX);
+       if (path_max <= 0 || path_max >= 4096)
+               path_max = 4096;
+#endif
+       rpath = dss_malloc(path_max);
+       rpath_limit = rpath + path_max;
+
+       if (name[0] != '/') {
+               if (!getcwd(rpath, path_max)) {
+                       ret = -ERRNO_TO_DSS_ERROR(errno);
+                       goto error;
+               }
+               dest = memchr(rpath, '\0', path_max);
+       } else {
+               rpath[0] = '/';
+               dest = rpath + 1;
+       }
+
+       for (start = end = name; *start; start = end) {
+               struct stat st;
+               int n;
+
+               /* Skip sequence of multiple path-separators.  */
+               while (*start == '/')
+                       ++start;
+
+               /* Find end of path component.  */
+               for (end = start; *end && *end != '/'; ++end)
+                       /* Nothing.  */ ;
+
+               if (end - start == 0)
+                       break;
+               else if (end - start == 1 && start[0] == '.')
+                       /* nothing */ ;
+               else if (end - start == 2 && start[0] == '.' && start[1] == '.') {
+                       /* Back up to previous component, ignore if at root already.  */
+                       if (dest > rpath + 1)
+                               while ((--dest)[-1] != '/') ;
+               } else {
+                       size_t new_size;
+
+                       if (dest[-1] != '/')
+                               *dest++ = '/';
+
+                       if (dest + (end - start) >= rpath_limit) {
+                               ptrdiff_t dest_offset = dest - rpath;
+
+                               new_size = rpath_limit - rpath;
+                               if (end - start + 1 > path_max)
+                                       new_size += end - start + 1;
+                               else
+                                       new_size += path_max;
+                               rpath = dss_realloc(rpath, new_size);
+                               rpath_limit = rpath + new_size;
+                               dest = rpath + dest_offset;
+                       }
+
+                       memcpy(dest, start, end - start);
+                       dest += end - start;
+                       *dest = '\0';
+
+                       if (stat(rpath, &st) < 0) {
+                               ret = -ERRNO_TO_DSS_ERROR(errno);
+                               goto error;
+                       }
+
+                       if (S_ISLNK(st.st_mode)) {
+                               char *buf = alloca(path_max);
+                               size_t len;
+
+                               if (++num_links > MAXSYMLINKS) {
+                                       ret = -ERRNO_TO_DSS_ERROR(ELOOP);
+                                       goto error;
+                               }
+
+                               n = readlink(rpath, buf, path_max - 1);
+                               if (n < 0) {
+                                       ret = -ERRNO_TO_DSS_ERROR(errno);
+                                       goto error;
+                               }
+                               buf[n] = '\0';
+
+                               if (!extra_buf)
+                                       extra_buf = alloca(path_max);
+
+                               len = strlen(end);
+                               if ((long int) (n + len) >= path_max) {
+                                       ret = -ERRNO_TO_DSS_ERROR(ENAMETOOLONG);
+                                       goto error;
+                               }
+
+                               /* Careful here, end may be a pointer into extra_buf... */
+                               memmove(&extra_buf[n], end, len + 1);
+                               name = end = memcpy(extra_buf, buf, n);
+
+                               if (buf[0] == '/') /* It's an absolute symlink */
+                                       dest = rpath + 1;
+                               else /* Back up to previous component, ignore if at root already: */
+                                       if (dest > rpath + 1)
+                                               while ((--dest)[-1] != '/')
+                                                       ; /* nothing */
+                       } else if (!S_ISDIR(st.st_mode) && *end != '\0') {
+                               ret = -ERRNO_TO_DSS_ERROR(ENOTDIR);
+                               goto error;
+                       }
+               }
+       }
+       if (dest > rpath + 1 && dest[-1] == '/')
+               --dest;
+       *dest = '\0';
+       *resolved_path = rpath;
+       return 1;
+error:
+       free(rpath);
+       *resolved_path = NULL;
+       return ret;
+}
+
+static inline int get_key_or_die(char *config_file)
+{
+       int ret;
+       struct stat statbuf;
+       char *rpath;
+
+       assert(config_file);
+       if (stat(config_file, &statbuf) == 0) {
+               ret = dss_realpath(config_file, &rpath);
+               if (ret < 0) {
+                       DSS_EMERG_LOG("could not resolve path %s: %s\n", config_file,
+                               dss_strerror(-ret));
+                       exit(EXIT_FAILURE);
+               }
+               DSS_DEBUG_LOG("resolved path: %s\n", rpath);
+       } else
+               /*
+                * This happens if the user did not specify a config file, and
+                * the default config file does not exist.  Another (unlikely)
+                * possibility is that the config file was removed between
+                * startup and this call. We don't care about these corner
+                * cases too much and just use the unresolved path in this
+                * case.
+                */
+               rpath = dss_strdup(config_file);
+       ret = super_fast_hash((uint8_t *)rpath, strlen(rpath), 0) >> 1;
+       free(rpath);
+       return ret;
+}
+
+static int mutex_get(int key, int flags)
+{
+       int ret;
+
+       DSS_DEBUG_LOG("getting semaphore 0x%x\n", key);
+       ret = semget(key, 2, flags);
+       if (ret < 0)
+               return -ERRNO_TO_DSS_ERROR(errno);
+       return ret;
+}
+
+static int do_semop(int id, struct sembuf *sops, int num)
+{
+       int ret;
+
+       DSS_DEBUG_LOG("calling semop\n");
+       do {
+               ret = semop(id, sops, num);
+               if (ret >= 0)
+                       return 1;
+       } while (errno == EINTR);
+       return -ERRNO_TO_DSS_ERROR(errno);
+}
+
+static int mutex_lock(int id)
+{
+       int ret;
+
+       DSS_DEBUG_LOG("locking\n");
+       struct sembuf sops[4] = {
+               {
+                       .sem_num = 0,
+                       .sem_op = 0,
+                       .sem_flg = SEM_UNDO | IPC_NOWAIT
+               },
+               {
+                       .sem_num = 0,
+                       .sem_op = 1,
+                       .sem_flg = SEM_UNDO | IPC_NOWAIT
+               },
+               {
+                       .sem_num = 1,
+                       .sem_op = 0,
+                       .sem_flg = SEM_UNDO | IPC_NOWAIT
+               },
+               {
+                       .sem_num = 1,
+                       .sem_op = 1,
+                       .sem_flg = SEM_UNDO | IPC_NOWAIT
+               }
+       };
+       ret = do_semop(id, sops, 4);
+       if (ret < 0)
+               return -ERRNO_TO_DSS_ERROR(errno);
+       return 1;
+}
+
+static int mutex_try_lock(int id)
+{
+       int ret;
+
+       DSS_DEBUG_LOG("trying to lock\n");
+       struct sembuf sops[2] = {
+               {
+                       .sem_num = 0,
+                       .sem_op = 0,
+                       .sem_flg = SEM_UNDO | IPC_NOWAIT
+               },
+               {
+                       .sem_num = 0,
+                       .sem_op = 1,
+                       .sem_flg = SEM_UNDO | IPC_NOWAIT
+               }
+       };
+       ret = do_semop(id, sops, 2);
+       if (ret < 0)
+               return -ERRNO_TO_DSS_ERROR(errno);
+       return 1;
+}
+
+int lock_dss(char *config_file)
+{
+       int ret, key = get_key_or_die(config_file);
+
+       ret = mutex_get(key, IPC_CREAT | 0600);
+       if (ret < 0)
+               return ret;
+       return mutex_lock(ret);
+}
+
+int get_dss_pid(char *config_file, pid_t *pid)
+{
+       int ret, semid, key = get_key_or_die(config_file);
+
+       ret = mutex_get(key, 0);
+       if (ret < 0)
+               return ret;
+       semid = ret;
+       ret = semctl(semid, 1, GETPID);
+       if (ret < 0)
+               return -E_NOT_RUNNING;
+       *pid = ret;
+       ret = mutex_try_lock(semid);
+       if (ret >= 0)
+               return -E_NOT_RUNNING;
+       return 1;
+}
diff --git a/ipc.h b/ipc.h
new file mode 100644 (file)
index 0000000..8646a8e
--- /dev/null
+++ b/ipc.h
@@ -0,0 +1,2 @@
+int lock_dss(char *config_file);
+int get_dss_pid(char *config_file, pid_t *pid);