mirrors/git
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

lockfile: allow file locking to be retried with a timeout

Browse Source 
Currently, there is only one attempt to lock a file. If it fails, the
whole operation fails.

But it might sometimes be advantageous to try acquiring a file lock a
few times before giving up. So add a new function,
hold_lock_file_for_update_timeout(), that allows a timeout to be
specified. Make hold_lock_file_for_update() a thin wrapper around the
new function.

If timeout_ms is positive, then retry for at least that many
milliseconds to acquire the lock. On each failed attempt, use select()
to wait for a backoff time that increases quadratically (capped at 1
second) and has a random component to prevent two processes from
getting synchronized. If timeout_ms is negative, retry indefinitely.

In a moment we will switch to using the new function when locking
packed-refs.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Michael Haggerty
2015-05-11 12:35:25 +02:00
committed by Junio C Hamano
parent 1ea28e1494
commit 044b6a9efe
2 changed files with 91 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
lockfile.h
View File

@ -74,8 +74,20 @@ struct lock_file {
extern void unable_to_lock_message(const char *path, int err,
struct strbuf *buf);
extern NORETURN void unable_to_lock_die(const char *path, int err);
extern int hold_lock_file_for_update(struct lock_file *, const char *path, int);
extern int hold_lock_file_for_append(struct lock_file *, const char *path, int);
extern int hold_lock_file_for_update_timeout(
struct lock_file *lk, const char *path,
int flags, long timeout_ms);
static inline int hold_lock_file_for_update(
struct lock_file *lk, const char *path,
int flags)
{
return hold_lock_file_for_update_timeout(lk, path, flags, 0);
}
extern int hold_lock_file_for_append(struct lock_file *lk, const char *path,
int flags);
extern FILE *fdopen_lock_file(struct lock_file *, const char *mode);
extern char *get_locked_file_path(struct lock_file *);
extern int commit_lock_file_to(struct lock_file *, const char *path);