From: Andre Noll Date: Fri, 10 Aug 2012 11:49:54 +0000 (+0200) Subject: Merge branch 't/ipc' X-Git-Tag: v0.1.5~13 X-Git-Url: http://git.tuebingen.mpg.de/?p=dss.git;a=commitdiff_plain;h=79489a96d14274b78a654bbcf60d8eb8289cae50;hp=2b4f4c85be13bb26a230df6669a7138d123c1a7d Merge branch 't/ipc' 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. --- diff --git a/Makefile b/Makefile index 99b8286..25d6ea9 100644 --- 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 --- 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 --- 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 --- 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 index 0000000..c438939 --- /dev/null +++ b/ipc.c @@ -0,0 +1,365 @@ +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#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 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);