/*
* Copyright (c) 2005, Junio C Hamano
*/
-#include "cache.h"
-#include "sigchain.h"
-
-static struct lock_file *lock_file_list;
-
-static void remove_lock_file(void)
-{
- pid_t me = getpid();
-
- while (lock_file_list) {
- if (lock_file_list->owner == me &&
- lock_file_list->filename[0]) {
- if (lock_file_list->fd >= 0)
- close(lock_file_list->fd);
- unlink_or_warn(lock_file_list->filename);
- }
- lock_file_list = lock_file_list->next;
- }
-}
-static void remove_lock_file_on_signal(int signo)
-{
- remove_lock_file();
- sigchain_pop(signo);
- raise(signo);
-}
+#include "cache.h"
+#include "lockfile.h"
/*
- * p = absolute or relative path name
+ * path = absolute or relative path name
*
- * Return a pointer into p showing the beginning of the last path name
- * element. If p is empty or the root directory ("/"), just return p.
+ * Remove the last path name element from path (leaving the preceding
+ * "/", if any). If path is empty or the root directory ("/"), set
+ * path to the empty string.
*/
-static char *last_path_elm(char *p)
+static void trim_last_path_component(struct strbuf *path)
{
- /* r starts pointing to null at the end of the string */
- char *r = strchr(p, '\0');
-
- if (r == p)
- return p; /* just return empty string */
-
- r--; /* back up to last non-null character */
+ int i = path->len;
/* back up past trailing slashes, if any */
- while (r > p && *r == '/')
- r--;
+ while (i && path->buf[i - 1] == '/')
+ i--;
/*
- * then go backwards until I hit a slash, or the beginning of
- * the string
+ * then go backwards until a slash, or the beginning of the
+ * string
*/
- while (r > p && *(r-1) != '/')
- r--;
- return r;
+ while (i && path->buf[i - 1] != '/')
+ i--;
+
+ strbuf_setlen(path, i);
}
#define MAXDEPTH 5
/*
- * p = path that may be a symlink
- * s = full size of p
+ * path contains a path that might be a symlink.
*
- * If p is a symlink, attempt to overwrite p with a path to the real
- * file or directory (which may or may not exist), following a chain of
- * symlinks if necessary. Otherwise, leave p unmodified.
+ * If path is a symlink, attempt to overwrite it with a path to the
+ * real file or directory (which may or may not exist), following a
+ * chain of symlinks if necessary. Otherwise, leave path unmodified.
*
- * This is a best-effort routine. If an error occurs, p will either be
- * left unmodified or will name a different symlink in a symlink chain
- * that started with p's initial contents.
- *
- * Always returns p.
+ * This is a best-effort routine. If an error occurs, path will
+ * either be left unmodified or will name a different symlink in a
+ * symlink chain that started with the original path.
*/
-
-static char *resolve_symlink(char *p, size_t s)
+static void resolve_symlink(struct strbuf *path)
{
int depth = MAXDEPTH;
+ static struct strbuf link = STRBUF_INIT;
while (depth--) {
- char link[PATH_MAX];
- int link_len = readlink(p, link, sizeof(link));
- if (link_len < 0) {
- /* not a symlink anymore */
- return p;
- }
- else if (link_len < sizeof(link))
- /* readlink() never null-terminates */
- link[link_len] = '\0';
- else {
- warning("%s: symlink too long", p);
- return p;
- }
-
- if (is_absolute_path(link)) {
+ if (strbuf_readlink(&link, path->buf, path->len) < 0)
+ break;
+
+ if (is_absolute_path(link.buf))
/* absolute path simply replaces p */
- if (link_len < s)
- strcpy(p, link);
- else {
- warning("%s: symlink too long", p);
- return p;
- }
- } else {
+ strbuf_reset(path);
+ else
/*
- * link is a relative path, so I must replace the
+ * link is a relative path, so replace the
* last element of p with it.
*/
- char *r = (char *)last_path_elm(p);
- if (r - p + link_len < s)
- strcpy(r, link);
- else {
- warning("%s: symlink too long", p);
- return p;
- }
- }
+ trim_last_path_component(path);
+
+ strbuf_addbuf(path, &link);
}
- return p;
+ strbuf_reset(&link);
}
/* Make sure errno contains a meaningful value on error */
static int lock_file(struct lock_file *lk, const char *path, int flags)
{
- /*
- * subtract 5 from size to make sure there's room for adding
- * ".lock" for the lock file name
- */
- static const size_t max_path_len = sizeof(lk->filename) - 5;
+ int fd;
+ struct strbuf filename = STRBUF_INIT;
- if (strlen(path) >= max_path_len) {
- errno = ENAMETOOLONG;
- return -1;
+ strbuf_addstr(&filename, path);
+ if (!(flags & LOCK_NO_DEREF))
+ resolve_symlink(&filename);
+
+ strbuf_addstr(&filename, LOCK_SUFFIX);
+ fd = create_tempfile(&lk->tempfile, filename.buf);
+ strbuf_release(&filename);
+ return fd;
+}
+
+/*
+ * Constants defining the gaps between attempts to lock a file. The
+ * first backoff period is approximately INITIAL_BACKOFF_MS
+ * milliseconds. The longest backoff period is approximately
+ * (BACKOFF_MAX_MULTIPLIER * INITIAL_BACKOFF_MS) milliseconds.
+ */
+#define INITIAL_BACKOFF_MS 1L
+#define BACKOFF_MAX_MULTIPLIER 1000
+
+/*
+ * Try locking path, retrying with quadratic backoff for at least
+ * timeout_ms milliseconds. If timeout_ms is 0, try locking the file
+ * exactly once. If timeout_ms is -1, try indefinitely.
+ */
+static int lock_file_timeout(struct lock_file *lk, const char *path,
+ int flags, long timeout_ms)
+{
+ int n = 1;
+ int multiplier = 1;
+ long remaining_ms = 0;
+ static int random_initialized = 0;
+
+ if (timeout_ms == 0)
+ return lock_file(lk, path, flags);
+
+ if (!random_initialized) {
+ srand((unsigned int)getpid());
+ random_initialized = 1;
}
- strcpy(lk->filename, path);
- if (!(flags & LOCK_NODEREF))
- resolve_symlink(lk->filename, max_path_len);
- strcat(lk->filename, ".lock");
- lk->fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666);
- if (0 <= lk->fd) {
- if (!lock_file_list) {
- sigchain_push_common(remove_lock_file_on_signal);
- atexit(remove_lock_file);
- }
- lk->owner = getpid();
- if (!lk->on_list) {
- lk->next = lock_file_list;
- lock_file_list = lk;
- lk->on_list = 1;
- }
- if (adjust_shared_perm(lk->filename)) {
- int save_errno = errno;
- error("cannot fix permission bits on %s",
- lk->filename);
- errno = save_errno;
- return -1;
- }
+
+ if (timeout_ms > 0)
+ remaining_ms = timeout_ms;
+
+ while (1) {
+ long backoff_ms, wait_ms;
+ int fd;
+
+ fd = lock_file(lk, path, flags);
+
+ if (fd >= 0)
+ return fd; /* success */
+ else if (errno != EEXIST)
+ return -1; /* failure other than lock held */
+ else if (timeout_ms > 0 && remaining_ms <= 0)
+ return -1; /* failure due to timeout */
+
+ backoff_ms = multiplier * INITIAL_BACKOFF_MS;
+ /* back off for between 0.75*backoff_ms and 1.25*backoff_ms */
+ wait_ms = (750 + rand() % 500) * backoff_ms / 1000;
+ sleep_millisec(wait_ms);
+ remaining_ms -= wait_ms;
+
+ /* Recursion: (n+1)^2 = n^2 + 2n + 1 */
+ multiplier += 2*n + 1;
+ if (multiplier > BACKOFF_MAX_MULTIPLIER)
+ multiplier = BACKOFF_MAX_MULTIPLIER;
+ else
+ n++;
}
- else
- lk->filename[0] = 0;
- return lk->fd;
}
void unable_to_lock_message(const char *path, int err, struct strbuf *buf)
absolute_path(path), strerror(err));
}
-int unable_to_lock_error(const char *path, int err)
-{
- struct strbuf buf = STRBUF_INIT;
-
- unable_to_lock_message(path, err, &buf);
- error("%s", buf.buf);
- strbuf_release(&buf);
- return -1;
-}
-
-NORETURN void unable_to_lock_index_die(const char *path, int err)
+NORETURN void unable_to_lock_die(const char *path, int err)
{
struct strbuf buf = STRBUF_INIT;
}
/* This should return a meaningful errno on failure */
-int hold_lock_file_for_update(struct lock_file *lk, const char *path, int flags)
+int hold_lock_file_for_update_timeout(struct lock_file *lk, const char *path,
+ int flags, long timeout_ms)
{
- int fd = lock_file(lk, path, flags);
+ int fd = lock_file_timeout(lk, path, flags, timeout_ms);
if (fd < 0 && (flags & LOCK_DIE_ON_ERROR))
- unable_to_lock_index_die(path, errno);
- return fd;
-}
-
-int hold_lock_file_for_append(struct lock_file *lk, const char *path, int flags)
-{
- int fd, orig_fd;
-
- fd = lock_file(lk, path, flags);
- if (fd < 0) {
- if (flags & LOCK_DIE_ON_ERROR)
- unable_to_lock_index_die(path, errno);
- return fd;
- }
-
- orig_fd = open(path, O_RDONLY);
- if (orig_fd < 0) {
- if (errno != ENOENT) {
- if (flags & LOCK_DIE_ON_ERROR)
- die("cannot open '%s' for copying", path);
- close(fd);
- return error("cannot open '%s' for copying", path);
- }
- } else if (copy_fd(orig_fd, fd)) {
- if (flags & LOCK_DIE_ON_ERROR)
- exit(128);
- close(fd);
- return -1;
- }
+ unable_to_lock_die(path, errno);
return fd;
}
-int close_lock_file(struct lock_file *lk)
+char *get_locked_file_path(struct lock_file *lk)
{
- int fd = lk->fd;
- lk->fd = -1;
- return close(fd);
+ struct strbuf ret = STRBUF_INIT;
+
+ strbuf_addstr(&ret, get_tempfile_path(&lk->tempfile));
+ if (ret.len <= LOCK_SUFFIX_LEN ||
+ strcmp(ret.buf + ret.len - LOCK_SUFFIX_LEN, LOCK_SUFFIX))
+ die("BUG: get_locked_file_path() called for malformed lock object");
+ /* remove ".lock": */
+ strbuf_setlen(&ret, ret.len - LOCK_SUFFIX_LEN);
+ return strbuf_detach(&ret, NULL);
}
int commit_lock_file(struct lock_file *lk)
{
- char result_file[PATH_MAX];
- size_t i;
- if (lk->fd >= 0 && close_lock_file(lk))
- return -1;
- strcpy(result_file, lk->filename);
- i = strlen(result_file) - 5; /* .lock */
- result_file[i] = 0;
- if (rename(lk->filename, result_file))
- return -1;
- lk->filename[0] = 0;
- return 0;
-}
-
-int hold_locked_index(struct lock_file *lk, int die_on_error)
-{
- return hold_lock_file_for_update(lk, get_index_file(),
- die_on_error
- ? LOCK_DIE_ON_ERROR
- : 0);
-}
+ char *result_path = get_locked_file_path(lk);
-void rollback_lock_file(struct lock_file *lk)
-{
- if (lk->filename[0]) {
- if (lk->fd >= 0)
- close(lk->fd);
- unlink_or_warn(lk->filename);
+ if (commit_lock_file_to(lk, result_path)) {
+ int save_errno = errno;
+ free(result_path);
+ errno = save_errno;
+ return -1;
}
- lk->filename[0] = 0;
+ free(result_path);
+ return 0;
}