diff options
| author | Patrick Steinhardt <ps@pks.im> | 2024-11-18 16:34:08 +0100 |
|---|---|---|
| committer | Junio C Hamano <gitster@pobox.com> | 2024-11-19 12:23:11 +0900 |
| commit | 988e7f5e952bbb7b6ae885f4da744f536f22693f (patch) | |
| tree | 7f0728eb78d9b5f5f3dc77003e712f774519e5ea /reftable/system.h | |
| parent | 6361226b79d24eb93a14e0b7d25f584269f9d5e6 (diff) | |
| download | git-988e7f5e952bbb7b6ae885f4da744f536f22693f.tar.gz | |
reftable/system: provide thin wrapper for lockfile subsystem
We use the lockfile subsystem to write lockfiles for "tables.list". As
with the tempfile subsystem, the lockfile subsystem also hooks into our
infrastructure to prune stale locks via atexit(3p) or signal handlers.
Furthermore, the lockfile subsystem also handles locking timeouts, which
do add quite a bit of logic. Having to reimplement that in the context
of Git wouldn't make a whole lot of sense, and it is quite likely that
downstream users of the reftable library may have a better idea for how
exactly to implement timeouts.
So again, provide a thin wrapper for the lockfile subsystem instead such
that the compatibility shim is fully self-contained.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'reftable/system.h')
| -rw-r--r-- | reftable/system.h | 45 |
1 files changed, 44 insertions, 1 deletions
diff --git a/reftable/system.h b/reftable/system.h index 858189fd55..7d5f803eeb 100644 --- a/reftable/system.h +++ b/reftable/system.h @@ -12,7 +12,6 @@ https://developers.google.com/open-source/licenses/bsd /* This header glues the reftable library to the rest of Git */ #include "git-compat-util.h" -#include "lockfile.h" /* * An implementation-specific temporary file. By making this specific to the @@ -55,4 +54,48 @@ int tmpfile_delete(struct reftable_tmpfile *t); */ int tmpfile_rename(struct reftable_tmpfile *t, const char *path); +/* + * An implementation-specific file lock. Same as with `reftable_tmpfile`, + * making this specific to the implementation makes it possible to tie this + * into signal or atexit handlers such that we know to clean up stale locks on + * abnormal exits. + */ +struct reftable_flock { + const char *path; + int fd; + void *priv; +}; +#define REFTABLE_FLOCK_INIT ((struct reftable_flock){ .fd = -1, }) + +/* + * Acquire the lock for the given target path by exclusively creating a file + * with ".lock" appended to it. If that lock exists, we wait up to `timeout_ms` + * to acquire the lock. If `timeout_ms` is 0 we don't wait, if it is negative + * we block indefinitely. + * + * Retrun 0 on success, a reftable error code on error. + */ +int flock_acquire(struct reftable_flock *l, const char *target_path, + long timeout_ms); + +/* + * Close the lockfile's file descriptor without removing the lock itself. This + * is a no-op in case the lockfile has already been closed beforehand. Returns + * 0 on success, a reftable error code on error. + */ +int flock_close(struct reftable_flock *l); + +/* + * Release the lock by unlinking the lockfile. This is a no-op in case the + * lockfile has already been released or committed beforehand. Returns 0 on + * success, a reftable error code on error. + */ +int flock_release(struct reftable_flock *l); + +/* + * Commit the lock by renaming the lockfile into place. Returns 0 on success, a + * reftable error code on error. + */ +int flock_commit(struct reftable_flock *l); + #endif |