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Re: [PATCH 07/23] expire_reflog(): use a lock_file for rewriting the reflog file

From
Stefan Beller <sbeller@google.com>
Date
Dec 5, 2014, 19:41 UTC
Message-ID
<CAGZ79kbf_Ze6JR33Y6-N3JZTUQqTyqc-feQZ-__h7JkeUTzUvg@mail.gmail.com>
In-Reply-To
<xmqqoarhq4dc.fsf@gitster.dls.corp.google.com>
On Fri, Dec 5, 2014 at 11:32 AM, Junio C Hamano <gitster@pobox.com> wrote:
Show 23 quoted lines
> Stefan Beller <sbeller@google.com> writes:
>
>>> > +static struct lock_file reflog_lock;
>>>
>>> If this lockfile is only used in that one function, it can be declared
>>> inside the function.
>>>
>>> If it is meant to be used throughout the 'git reflog' command, then it
>>> can go near the top of the file.
>>>
>>
>> After the series completes, this lock is only used in reflog_expire.
>> So I'd rather move it inside the function? Then we could run the reflog_expire
>> function in parallel for different locks in theory?
>
> I am not sure about the "parallel" part, but I would imagine that it
> is an essential prerequisite to move this outside the "client" code
> if we want to later replace the backing storage of refs and reflogs
> outside the filesystem, so from that point of view,  I think the
> suggestion makes sense.
>
> Thanks.
>

Sorry for the confusion. With parallel I mean, that in theory we could have multiple threads running reflog expire at the same time in the same program. Having the "static struct lock_file reflog_lock;" around, we can only process one reflog at a time, as that is holding the lock_file struct.

I am not saying we want to go multi-threading any time soon if at all. Just that it would be easier to do, if not having the lock file as a file-global variable instead of a variable inside a function.

Thanks, Stefan

Previous: Junio C HamanoNext: Junio C Hamano
Message 23 of 63 in “Add reflog_expire() to the references API”
  1. 00/23 Add reflog_expire() to the references APIMichael Haggerty, Dec 4, 2014
  2. 01/23 refs.c: make ref_transaction_create a wrapper for ref_transaction_updateMichael Haggerty, Dec 4, 2014
  3. 02/23 refs.c: make ref_transaction_delete a wrapper for ref_transaction_updateMichael Haggerty, Dec 4, 2014
  4. 03/23 refs.c: add a function to append a reflog entry to a fdMichael Haggerty, Dec 4, 2014
  5. 04/23 expire_reflog(): remove unused parameterMichael Haggerty, Dec 4, 2014
  6. Jonathan NiederDec 4, 2014
  7. Jonathan NiederDec 4, 2014
  8. Michael HaggertyDec 5, 2014
  9. 05/23 expire_reflog(): rename "ref" parameter to "refname"Michael Haggerty, Dec 4, 2014
  10. Jonathan NiederDec 4, 2014
  11. 06/23 expire_reflog(): exit early if the reference has no reflogMichael Haggerty, Dec 4, 2014
  12. Jonathan NiederDec 4, 2014
  13. Jonathan NiederDec 4, 2014
  14. Michael HaggertyDec 5, 2014
  15. 07/23 expire_reflog(): use a lock_file for rewriting the reflog fileMichael Haggerty, Dec 4, 2014
  16. Jonathan NiederDec 5, 2014
  17. Stefan BellerDec 5, 2014
  18. Michael HaggertyDec 8, 2014
  19. Junio C HamanoDec 9, 2014
  20. Jeff KingDec 9, 2014
  21. Stefan BellerDec 5, 2014
  22. Junio C HamanoDec 5, 2014
  23. Stefan BellerDec 5, 2014
  24. Junio C HamanoDec 5, 2014
  25. Michael HaggertyDec 8, 2014
  26. ronnie sahlbergDec 5, 2014
  27. Michael HaggertyDec 8, 2014
  28. 08/23 Extract function should_expire_reflog_ent()Michael Haggerty, Dec 4, 2014
  29. Stefan BellerDec 8, 2014
  30. 09/23 expire_reflog(): extract two policy-related functionsMichael Haggerty, Dec 4, 2014
  31. Stefan BellerDec 5, 2014
  32. 10/23 expire_reflog(): add a "flags" argumentMichael Haggerty, Dec 4, 2014
  33. Stefan BellerDec 8, 2014
  34. 11/23 expire_reflog(): move dry_run to flags argumentMichael Haggerty, Dec 4, 2014
  35. Stefan BellerDec 8, 2014
  36. 12/23 expire_reflog(): move updateref to flags argumentMichael Haggerty, Dec 4, 2014
  37. Stefan BellerDec 8, 2014
  38. 13/23 Rename expire_reflog_cb to expire_reflog_policy_cbMichael Haggerty, Dec 4, 2014
  39. Stefan BellerDec 8, 2014
  40. 14/23 struct expire_reflog_cb: a new callback data typeMichael Haggerty, Dec 4, 2014
  41. Stefan BellerDec 8, 2014
  42. 15/23 expire_reflog(): pass flags through to expire_reflog_ent()Michael Haggerty, Dec 4, 2014
  43. Stefan BellerDec 8, 2014
  44. 16/23 expire_reflog(): move verbose to flags argumentMichael Haggerty, Dec 4, 2014
  45. Stefan BellerDec 8, 2014
  46. 17/23 expire_reflog(): move rewrite to flags argumentMichael Haggerty, Dec 4, 2014
  47. Stefan BellerDec 8, 2014
  48. 18/23 Move newlog and last_kept_sha1 to "struct expire_reflog_cb"Michael Haggerty, Dec 4, 2014
  49. Stefan BellerDec 8, 2014
  50. 19/23 expire_reflog(): treat the policy callback data as opaqueMichael Haggerty, Dec 4, 2014
  51. Stefan BellerDec 8, 2014
  52. 20/23 reflog_expire(): new function in the reference APIMichael Haggerty, Dec 4, 2014
  53. Stefan BellerDec 8, 2014
  54. Michael HaggertyDec 12, 2014
  55. Jeff KingDec 12, 2014
  56. Junio C HamanoDec 12, 2014
  57. 21/23 refs.c: remove unlock_ref/close_ref/commit_ref from the refs apiMichael Haggerty, Dec 4, 2014
  58. 22/23 lock_any_ref_for_update(): inline functionMichael Haggerty, Dec 4, 2014
  59. Stefan BellerDec 8, 2014
  60. Michael HaggertyDec 11, 2014
  61. 23/23 refs.c: don't expose the internal struct ref_lock in the header fileMichael Haggerty, Dec 4, 2014
  62. Junio C HamanoDec 4, 2014
  63. Stefan BellerDec 5, 2014

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