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[PATCH v3 07/25] lock_file(): always add lock_file object to lock_file_list

From
Michael Haggerty <mhagger@alum.mit.edu>
Date
Apr 14, 2014, 13:54 UTC
Message-ID
<1397483695-10888-8-git-send-email-mhagger@alum.mit.edu>
In-Reply-To
<1397483695-10888-1-git-send-email-mhagger@alum.mit.edu>

It used to be that if locking failed, lock_file() usually did not register the lock_file object in lock_file_list but sometimes it did. This confusion was compounded if lock_file() was called via hold_lock_file_for_append(), which has its own failure modes.

The ambiguity didn't have any ill effects, because lock_file objects cannot be removed from the lock_file_list anyway. But it is unnecessary to leave this behavior inconsistent.

So change lock_file() to *always* ensure that the lock_file object is registered in lock_file_list regardless of whether an error occurs.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 lockfile.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)
diff --git a/lockfile.c b/lockfile.c
index e78a35f..120a6d6 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -130,6 +130,22 @@ static int lock_file(struct lock_file *lk, const char *path, int flags)
 	 */
 	static const size_t max_path_len = sizeof(lk->filename) - 5;
 
+	if (!lock_file_list) {
+		/* One-time initialization */
+		sigchain_push_common(remove_lock_file_on_signal);
+		atexit(remove_lock_file);
+	}
+
+	if (!lk->on_list) {
+		/* Initialize *lk and add it to lock_file_list: */
+		lk->fd = -1;
+		lk->owner = 0;
+		lk->on_list = 1;
+		lk->filename[0] = 0;
+		lk->next = lock_file_list;
+		lock_file_list = lk;
+	}
+
 	if (strlen(path) >= max_path_len)
 		return -1;
 	strcpy(lk->filename, path);
@@ -138,16 +154,7 @@ static int lock_file(struct lock_file *lk, const char *path, int flags)
 	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)) {
 			error("cannot fix permission bits on %s", lk->filename);
 			rollback_lock_file(lk);

-- 
1.9.1
Previous: Michael HaggertyNext: Michael Haggerty
Message 8 of 32 in “Lockfile correctness and refactoring”
  1. 00/25 Lockfile correctness and refactoringMichael Haggerty, Apr 14, 2014
  2. 01/25 unable_to_lock_die(): rename function from unable_to_lock_index_die()Michael Haggerty, Apr 14, 2014
  3. 02/25 api-lockfile: expand the documentationMichael Haggerty, Apr 14, 2014
  4. 03/25 rollback_lock_file(): do not clear filename redundantlyMichael Haggerty, Apr 14, 2014
  5. 04/25 rollback_lock_file(): set fd to -1Michael Haggerty, Apr 14, 2014
  6. 05/25 lockfile: unlock file if lockfile permissions cannot be adjustedMichael Haggerty, Apr 14, 2014
  7. 06/25 hold_lock_file_for_append(): release lock on errorsMichael Haggerty, Apr 14, 2014
  8. 07/25 lock_file(): always add lock_file object to lock_file_listMichael Haggerty, Apr 14, 2014
  9. 08/25 lockfile.c: document the various states of lock_file objectsMichael Haggerty, Apr 14, 2014
  10. 09/25 cache.h: define constants LOCK_SUFFIX and LOCK_SUFFIX_LENMichael Haggerty, Apr 14, 2014
  11. 10/25 delete_ref_loose(): don't muck around in the lock_file's filenameMichael Haggerty, Apr 14, 2014
  12. 11/25 prepare_index(): declare return value to be (const char *)Michael Haggerty, Apr 14, 2014
  13. 12/25 write_packed_entry_fn(): convert cb_data into a (const int *)Michael Haggerty, Apr 14, 2014
  14. 13/25 lock_file(): exit early if lockfile cannot be openedMichael Haggerty, Apr 14, 2014
  15. 14/25 remove_lock_file(): call rollback_lock_file()Michael Haggerty, Apr 14, 2014
  16. 15/25 commit_lock_file(): inline temporary variableMichael Haggerty, Apr 14, 2014
  17. 16/25 commit_lock_file(): die() if called for unlocked lockfile objectMichael Haggerty, Apr 14, 2014
  18. Johannes SixtApr 15, 2014
  19. Michael HaggertyApr 16, 2014
  20. 17/25 lockfile: avoid transitory invalid statesMichael Haggerty, Apr 14, 2014
  21. 18/25 struct lock_file: declare some fields volatileMichael Haggerty, Apr 14, 2014
  22. Johannes SixtApr 15, 2014
  23. Michael HaggertyApr 16, 2014
  24. 19/25 try_merge_strategy(): remove redundant lock_file allocationMichael Haggerty, Apr 14, 2014
  25. 20/25 try_merge_strategy(): use a statically-allocated lock_file objectMichael Haggerty, Apr 14, 2014
  26. 21/25 commit_lock_file(): use a strbuf to manage temporary spaceMichael Haggerty, Apr 14, 2014
  27. 22/25 Change lock_file::filename into a strbufMichael Haggerty, Apr 14, 2014
  28. 23/25 resolve_symlink(): use a strbuf for internal scratch spaceMichael Haggerty, Apr 14, 2014
  29. 24/25 resolve_symlink(): take a strbuf parameterMichael Haggerty, Apr 14, 2014
  30. 25/25 trim_last_path_elm(): replace last_path_elm()Michael Haggerty, Apr 14, 2014
  31. Torsten BögershausenApr 15, 2014
  32. Michael HaggertyApr 16, 2014

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