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Re: [PATCH v4 06/32] lockfile: unlock file if lockfile permissions cannot be adjusted

From
Michael Haggerty <mhagger@alum.mit.edu>
Date
Sep 12, 2014, 11:03 UTC
Message-ID
<5412D2F3.50404@alum.mit.edu>
In-Reply-To
<xmqqr3zkifl5.fsf@gitster.dls.corp.google.com>
On 09/10/2014 12:39 AM, Junio C Hamano wrote:
Show 13 quoted lines
> Michael Haggerty <mhagger@alum.mit.edu> writes:
> 
>> If the call to adjust_shared_perm() fails, lock_file returns -1, which
>> to the caller looks like any other failure to lock the file.  So in
>> this case, roll back the lockfile before returning so that the lock
>> file is deleted immediately and the lockfile object is left in a
>> predictable state (namely, unlocked).  Previously, the lockfile was
>> retained until process cleanup in this situation.
> 
> ... which would mean that other processes can grab a lock on the
> same file a bit earlier. Is there any negative implication caused by
> that difference?  I do not think of any but I could be missing
> something.

I think the end effect would be the same as if another process had grabbed the lock a nanosecond before this process tried to do so. So assuming that callers handle that situation correctly, I don't think this change can cause any problems.

Michael
-- 
Michael Haggerty
mhagger@alum.mit.edu
Previous: Junio C HamanoNext: Michael Haggerty
Message 12 of 66 in “Lockfile correctness and refactoring”
  1. 00/32 Lockfile correctness and refactoringMichael Haggerty, Sep 6, 2014
  2. 01/32 unable_to_lock_die(): rename function from unable_to_lock_index_die()Michael Haggerty, Sep 6, 2014
  3. 02/32 api-lockfile: expand the documentationMichael Haggerty, Sep 6, 2014
  4. Junio C HamanoSep 9, 2014
  5. 03/32 rollback_lock_file(): do not clear filename redundantlyMichael Haggerty, Sep 6, 2014
  6. Ronnie SahlbergSep 11, 2014
  7. 04/32 rollback_lock_file(): exit early if lock is not activeMichael Haggerty, Sep 6, 2014
  8. Ronnie SahlbergSep 11, 2014
  9. 05/32 rollback_lock_file(): set fd to -1Michael Haggerty, Sep 6, 2014
  10. 06/32 lockfile: unlock file if lockfile permissions cannot be adjustedMichael Haggerty, Sep 6, 2014
  11. Junio C HamanoSep 9, 2014
  12. Michael HaggertySep 12, 2014
  13. 07/32 hold_lock_file_for_append(): release lock on errorsMichael Haggerty, Sep 6, 2014
  14. Junio C HamanoSep 9, 2014
  15. Michael HaggertySep 12, 2014
  16. 08/32 lock_file(): always add lock_file object to lock_file_listMichael Haggerty, Sep 6, 2014
  17. 09/32 lockfile.c: document the various states of lock_file objectsMichael Haggerty, Sep 6, 2014
  18. Ronnie SahlbergSep 11, 2014
  19. 10/32 cache.h: define constants LOCK_SUFFIX and LOCK_SUFFIX_LENMichael Haggerty, Sep 6, 2014
  20. Ronnie SahlbergSep 11, 2014
  21. Michael HaggertySep 12, 2014
  22. Ronnie SahlbergSep 11, 2014
  23. Michael HaggertySep 12, 2014
  24. Ronnie SahlbergSep 12, 2014
  25. 11/32 delete_ref_loose(): don't muck around in the lock_file's filenameMichael Haggerty, Sep 6, 2014
  26. Johannes SixtSep 13, 2014
  27. Michael HaggertySep 14, 2014
  28. Michael HaggertySep 14, 2014
  29. Johannes SixtSep 14, 2014
  30. 12/32 prepare_index(): declare return value to be (const char *)Michael Haggerty, Sep 6, 2014
  31. 13/32 write_packed_entry_fn(): convert cb_data into a (const int *)Michael Haggerty, Sep 6, 2014
  32. Ronnie SahlbergSep 11, 2014
  33. 14/32 lock_file(): exit early if lockfile cannot be openedMichael Haggerty, Sep 6, 2014
  34. Ronnie SahlbergSep 11, 2014
  35. 15/32 remove_lock_file(): call rollback_lock_file()Michael Haggerty, Sep 6, 2014
  36. 16/32 commit_lock_file(): inline temporary variableMichael Haggerty, Sep 6, 2014
  37. 17/32 commit_lock_file(): die() if called for unlocked lockfile objectMichael Haggerty, Sep 6, 2014
  38. 18/32 commit_lock_file(): if close fails, roll backMichael Haggerty, Sep 6, 2014
  39. 19/32 commit_lock_file(): rollback lock file on failure to renameMichael Haggerty, Sep 6, 2014
  40. Jeff KingSep 10, 2014
  41. Duy NguyenSep 10, 2014
  42. 20/32 api-lockfile: document edge casesMichael Haggerty, Sep 6, 2014
  43. 21/32 dump_marks(): remove a redundant call to rollback_lock_file()Michael Haggerty, Sep 6, 2014
  44. 22/32 git_config_set_multivar_in_file(): avoid call to rollback_lock_file()Michael Haggerty, Sep 6, 2014
  45. 23/32 lockfile: avoid transitory invalid statesMichael Haggerty, Sep 6, 2014
  46. 24/32 struct lock_file: declare some fields volatileMichael Haggerty, Sep 6, 2014
  47. 25/32 try_merge_strategy(): remove redundant lock_file allocationMichael Haggerty, Sep 6, 2014
  48. 26/32 try_merge_strategy(): use a statically-allocated lock_file objectMichael Haggerty, Sep 6, 2014
  49. 27/32 commit_lock_file(): use a strbuf to manage temporary spaceMichael Haggerty, Sep 6, 2014
  50. 28/32 Change lock_file::filename into a strbufMichael Haggerty, Sep 6, 2014
  51. 29/32 resolve_symlink(): use a strbuf for internal scratch spaceMichael Haggerty, Sep 6, 2014
  52. 30/32 resolve_symlink(): take a strbuf parameterMichael Haggerty, Sep 6, 2014
  53. 31/32 trim_last_path_elm(): replace last_path_elm()Michael Haggerty, Sep 6, 2014
  54. 32/32 Extract a function commit_lock_file_to()Michael Haggerty, Sep 6, 2014
  55. Torsten BögershausenSep 7, 2014
  56. Michael HaggertySep 12, 2014
  57. Junio C HamanoSep 8, 2014
  58. Jeff KingSep 10, 2014
  59. Duy NguyenSep 10, 2014
  60. Jeff KingSep 10, 2014
  61. Junio C HamanoSep 10, 2014
  62. Jeff KingSep 10, 2014
  63. Michael HaggertySep 12, 2014
  64. Michael HaggertySep 12, 2014
  65. Michael HaggertySep 12, 2014
  66. Jeff KingSep 13, 2014

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