Merge branch 'mh/ref-lock-entry'

The code to acquire a lock on a reference (e.g. while accepting a
push from a client) used to immediately fail when the reference is
already locked---now it waits for a very short while and retries,
which can make it succeed if the lock holder was holding it during
a read-only operation.

* mh/ref-lock-entry:
refs: retry acquiring reference locks for 100ms

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 9b42e0ca73429d01f987b2b93c413ab49a98fef4..dc4e3f58a2d2e8a5a6753bd290d65fec4f7f7b21 100644 (file)
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -776,6 +776,12 @@ core.commentChar::
 If set to "auto", `git-commit` would select a character that is not
 the beginning character of any line in existing commit messages.
 
+core.filesRefLockTimeout::
+       The length of time, in milliseconds, to retry when trying to
+       lock an individual reference. Value 0 means not to retry at
+       all; -1 means to try indefinitely. Default is 100 (i.e.,
+       retry for 100ms).
+
 core.packedRefsTimeout::
        The length of time, in milliseconds, to retry when trying to
        lock the `packed-refs` file. Value 0 means not to retry at

diff --git a/refs.c b/refs.c
index 3d549a89701ab77c973835cd7c556b5a8c6ddd6f..b0106b8162c7b8e3770e04c212abb05f1afbd0c3 100644 (file)
--- a/refs.c
+++ b/refs.c
@@ -579,6 +579,21 @@ enum ref_type ref_type(const char *refname)
        return REF_TYPE_NORMAL;
 }
 
+long get_files_ref_lock_timeout_ms(void)
+{
+       static int configured = 0;
+
+       /* The default timeout is 100 ms: */
+       static int timeout_ms = 100;
+
+       if (!configured) {
+               git_config_get_int("core.filesreflocktimeout", &timeout_ms);
+               configured = 1;
+       }
+
+       return timeout_ms;
+}
+
 static int write_pseudoref(const char *pseudoref, const unsigned char *sha1,
                           const unsigned char *old_sha1, struct strbuf *err)
 {
@@ -591,7 +606,9 @@ static int write_pseudoref(const char *pseudoref, const unsigned char *sha1,
        strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
 
        filename = git_path("%s", pseudoref);
-       fd = hold_lock_file_for_update(&lock, filename, LOCK_DIE_ON_ERROR);
+       fd = hold_lock_file_for_update_timeout(&lock, filename,
+                                              LOCK_DIE_ON_ERROR,
+                                              get_files_ref_lock_timeout_ms());
        if (fd < 0) {
                strbuf_addf(err, "could not open '%s' for writing: %s",
                            filename, strerror(errno));
@@ -634,8 +651,9 @@ static int delete_pseudoref(const char *pseudoref, const unsigned char *old_sha1
                int fd;
                unsigned char actual_old_sha1[20];
 
-               fd = hold_lock_file_for_update(&lock, filename,
-                                              LOCK_DIE_ON_ERROR);
+               fd = hold_lock_file_for_update_timeout(
+                               &lock, filename, LOCK_DIE_ON_ERROR,
+                               get_files_ref_lock_timeout_ms());
                if (fd < 0)
                        die_errno(_("Could not open '%s' for writing"), filename);
                if (read_ref(pseudoref, actual_old_sha1))

diff --git a/refs/files-backend.c b/refs/files-backend.c
index 5cca55510b6a0683f16937215f6056d896c622e0..fccbc24ac4ad3631b96a4796f4b1f89913fa0ea3 100644 (file)
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -537,7 +537,9 @@ static int lock_raw_ref(struct files_ref_store *refs,
        if (!lock->lk)
                lock->lk = xcalloc(1, sizeof(struct lock_file));
 
-       if (hold_lock_file_for_update(lock->lk, ref_file.buf, LOCK_NO_DEREF) < 0) {
+       if (hold_lock_file_for_update_timeout(
+                           lock->lk, ref_file.buf, LOCK_NO_DEREF,
+                           get_files_ref_lock_timeout_ms()) < 0) {
                if (errno == ENOENT && --attempts_remaining > 0) {
                        /*
                         * Maybe somebody just deleted one of the
@@ -865,7 +867,9 @@ static int create_reflock(const char *path, void *cb)
 {
        struct lock_file *lk = cb;
 
-       return hold_lock_file_for_update(lk, path, LOCK_NO_DEREF) < 0 ? -1 : 0;
+       return hold_lock_file_for_update_timeout(
+                       lk, path, LOCK_NO_DEREF,
+                       get_files_ref_lock_timeout_ms()) < 0 ? -1 : 0;
 }
 
 /*

diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index 4789106fc093391f1c3e67d0fe46c8ece47fde34..b02dc5a7e3500cae1784199a82b37be020004df1 100644 (file)
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h
@@ -61,6 +61,12 @@
  */
 #define REF_DELETED_LOOSE 0x200
 
+/*
+ * Return the length of time to retry acquiring a loose reference lock
+ * before giving up, in milliseconds:
+ */
+long get_files_ref_lock_timeout_ms(void);
+
 /*
  * Return true iff refname is minimally safe. "Safe" here means that
  * deleting a loose reference by this name will not do any damage, for