From: Junio C Hamano <gitster@pobox•com>
To: Brad King <brad.king@kitware•com>
Cc: git@vger•kernel.org
Subject: Re: [PATCH v2 6/8] refs: add update_refs for multiple simultaneous updates
Date: Sat, 31 Aug 2013 23:08:34 -0700 [thread overview]
Message-ID: <xmqqob8dul99.fsf@gitster.dls.corp.google.com> (raw)
In-Reply-To: edaddbd4e303866f789f1a4f755a9da77590aeef.1377885441.git.brad.king@kitware.com
Brad King <brad.king@kitware•com> writes:
> Add 'struct ref_update' to encode the information needed to update or
> delete a ref (name, new sha1, optional old sha1, no-deref flag). Add
> function 'update_refs' accepting an array of updates to perform. First
> sort the input array to order locks consistently everywhere and reject
> multiple updates to the same ref. Then acquire locks on all refs with
> verified old values. Then update or delete all refs accordingly. Fail
> if any one lock cannot be obtained or any one old value does not match.
OK. The code releases the locks it acquired so far when it fails,
which is good.
> Though the refs themeselves cannot be modified together in a single
"themselves".
> atomic transaction, this function does enable some useful semantics.
> For example, a caller may create a new branch starting from the head of
> another branch and rewind the original branch at the same time. This
> transfers ownership of commits between branches without risk of losing
> commits added to the original branch by a concurrent process, or risk of
> a concurrent process creating the new branch first.
> +static int ref_update_compare(const void *r1, const void *r2)
> +{
> + struct ref_update *u1 = (struct ref_update *)(r1);
> + struct ref_update *u2 = (struct ref_update *)(r2);
> + int ret;
Let's have a blank line between the end of decls and the beginning
of the body here.
> + ret = strcmp(u1->ref_name, u2->ref_name);
> + if (ret)
> + return ret;
> + ret = hashcmp(u1->new_sha1, u2->new_sha1);
> + if (ret)
> + return ret;
> + ret = hashcmp(u1->old_sha1, u2->old_sha1);
> + if (ret)
> + return ret;
> + ret = u1->flags - u2->flags;
> + if (ret)
> + return ret;
> + return u1->have_old - u2->have_old;
> +}
I notice that we are using an array of structures and letting qsort
swap 50~64 bytes of data, instead of sorting an array of pointers,
each element of which points at a structure. This may not matter
unless we are asked to update thousands at once, so I think it is OK
for now.
> +static int ref_update_reject_duplicates(struct ref_update *updates, int n,
> + enum action_on_err onerr)
> +{
> + int i;
> + for (i = 1; i < n; ++i)
> + if (!strcmp(updates[i - 1].ref_name, updates[i].ref_name))
> + break;
Optionally we could silently dedup multiple identical updates and
not fail it in ref-update-reject-duplicates. But that does not have
to be done until we find people's script would benefit from such a
nicety.
By the way, unless there is a strong reason not to do so,
post-increment "i++" (and pre-decrement "--i", if you use it) is the
norm around here. Especially in places like the third part of a
for(;;) loop where people are used to see "i++", breaking the idiom
makes readers wonder if there is something else going on.
> + /* Perform updates first so live commits remain referenced: */
> + for (i = 0; i < n; ++i)
> + if (!is_null_sha1(updates[i].new_sha1)) {
> + ret |= update_ref_write(action,
> + updates[i].ref_name,
> + updates[i].new_sha1,
> + locks[i], onerr);
> + locks[i] = 0; /* freed by update_ref_write */
I think what is assigned here is a NULL pointer.
Will locally tweak while queuing. Thanks.
next prev parent reply other threads:[~2013-09-01 6:08 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-29 14:11 [PATCH/RFC 0/7] Multiple simultaneously locked ref updates Brad King
2013-08-29 14:11 ` [PATCH/RFC 1/7] reset: rename update_refs to reset_refs Brad King
2013-08-29 17:17 ` Junio C Hamano
2013-08-29 18:07 ` Brad King
2013-08-29 14:11 ` [PATCH/RFC 2/7] refs: report ref type from lock_any_ref_for_update Brad King
2013-08-29 17:22 ` Junio C Hamano
2013-08-29 18:08 ` Brad King
2013-08-29 14:11 ` [PATCH/RFC 3/7] refs: factor update_ref steps into helpers Brad King
2013-08-29 14:11 ` [PATCH/RFC 4/7] refs: factor delete_ref loose ref step into a helper Brad King
2013-08-29 17:28 ` Junio C Hamano
2013-08-29 18:08 ` Brad King
2013-08-29 14:11 ` [PATCH/RFC 5/7] refs: add function to repack without multiple refs Brad King
2013-08-29 17:34 ` Junio C Hamano
2013-08-29 18:09 ` Brad King
2013-08-29 14:11 ` [PATCH/RFC 6/7] refs: add update_refs for multiple simultaneous updates Brad King
2013-08-29 17:39 ` Junio C Hamano
2013-08-29 18:20 ` Brad King
2013-08-29 18:32 ` Junio C Hamano
2013-08-29 18:38 ` Brad King
2013-08-29 19:30 ` Brad King
2013-08-29 14:11 ` [PATCH/RFC 7/7] update-ref: support " Brad King
2013-08-29 18:34 ` Junio C Hamano
2013-08-29 18:42 ` Brad King
2013-08-29 15:32 ` [PATCH/RFC 0/7] Multiple simultaneously locked ref updates Martin Fick
2013-08-29 15:46 ` Brad King
2013-08-29 16:21 ` Junio C Hamano
2013-08-29 17:09 ` Brad King
2013-08-29 18:07 ` Junio C Hamano
2013-08-29 18:23 ` Brad King
2013-08-30 18:11 ` [PATCH v2 0/8] " Brad King
2013-08-30 18:11 ` [PATCH v2 1/8] reset: rename update_refs to reset_refs Brad King
2013-08-30 18:12 ` [PATCH v2 2/8] refs: report ref type from lock_any_ref_for_update Brad King
2013-08-30 18:12 ` [PATCH v2 3/8] refs: factor update_ref steps into helpers Brad King
2013-09-01 6:08 ` Junio C Hamano
2013-09-02 17:19 ` Brad King
2013-08-30 18:12 ` [PATCH v2 4/8] refs: factor delete_ref loose ref step into a helper Brad King
2013-08-31 16:30 ` Michael Haggerty
2013-09-02 17:19 ` Brad King
2013-08-30 18:12 ` [PATCH v2 5/8] refs: add function to repack without multiple refs Brad King
2013-08-30 18:12 ` [PATCH v2 6/8] refs: add update_refs for multiple simultaneous updates Brad King
2013-08-31 18:19 ` Michael Haggerty
2013-09-02 17:20 ` Brad King
2013-09-01 6:08 ` Junio C Hamano [this message]
2013-09-02 17:20 ` Brad King
2013-09-03 4:43 ` Michael Haggerty
2013-09-03 11:59 ` Brad King
2013-08-30 18:12 ` [PATCH v2 7/8] update-ref: support " Brad King
2013-08-30 22:51 ` Junio C Hamano
2013-09-02 17:23 ` Brad King
2013-08-31 18:42 ` Michael Haggerty
2013-09-02 17:21 ` Brad King
2013-08-30 18:12 ` [PATCH v2 8/8] update-ref: add test cases covering --stdin signature Brad King
2013-09-01 3:41 ` Eric Sunshine
2013-09-02 17:23 ` Brad King
2013-08-31 19:02 ` [PATCH v2 0/8] Multiple simultaneously locked ref updates Michael Haggerty
2013-09-02 17:48 ` [PATCH v3 " Brad King
2013-09-02 17:48 ` [PATCH v3 1/8] reset: rename update_refs to reset_refs Brad King
2013-09-02 17:48 ` [PATCH v3 2/8] refs: report ref type from lock_any_ref_for_update Brad King
2013-09-02 17:48 ` [PATCH v3 3/8] refs: factor update_ref steps into helpers Brad King
2013-09-02 17:48 ` [PATCH v3 4/8] refs: factor delete_ref loose ref step into a helper Brad King
2013-09-02 17:48 ` [PATCH v3 5/8] refs: add function to repack without multiple refs Brad King
2013-09-02 17:48 ` [PATCH v3 6/8] refs: add update_refs for multiple simultaneous updates Brad King
2013-09-02 17:48 ` [PATCH v3 7/8] update-ref: support " Brad King
2013-09-02 18:37 ` Brad King
2013-09-02 17:48 ` [PATCH v3 8/8] update-ref: add test cases covering --stdin signature Brad King
2013-09-03 8:16 ` Eric Sunshine
2013-09-03 12:15 ` Brad King
2013-09-04 15:22 ` [PATCH v4 0/8] Multiple simultaneously locked ref updates Brad King
2013-09-04 15:22 ` [PATCH v4 1/8] reset: rename update_refs to reset_refs Brad King
2013-09-04 15:22 ` [PATCH v4 2/8] refs: report ref type from lock_any_ref_for_update Brad King
2013-09-04 15:22 ` [PATCH v4 3/8] refs: factor update_ref steps into helpers Brad King
2013-09-04 15:22 ` [PATCH v4 4/8] refs: factor delete_ref loose ref step into a helper Brad King
2013-09-04 15:22 ` [PATCH v4 5/8] refs: add function to repack without multiple refs Brad King
2013-09-04 15:22 ` [PATCH v4 6/8] refs: add update_refs for multiple simultaneous updates Brad King
2013-09-04 15:22 ` [PATCH v4 7/8] update-ref: support " Brad King
2013-09-04 18:23 ` Junio C Hamano
2013-09-04 19:59 ` Brad King
2013-09-04 21:27 ` Junio C Hamano
2013-09-05 20:32 ` Brad King
2013-09-05 21:23 ` Junio C Hamano
2013-09-05 23:44 ` Brad King
2013-09-04 19:17 ` Junio C Hamano
2013-09-04 19:16 ` Brad King
2013-09-04 15:22 ` [PATCH v4 8/8] update-ref: add test cases covering --stdin signature Brad King
2013-09-09 13:22 ` [PATCH v5 0/8] Multiple simultaneously locked ref updates Brad King
2013-09-09 13:22 ` [PATCH v5 7/8] update-ref: support multiple simultaneous updates Brad King
2013-09-09 13:22 ` [PATCH v5 8/8] update-ref: add test cases covering --stdin signature Brad King
2013-09-10 0:57 ` [PATCH v6 0/8] Multiple simultaneously locked ref updates Brad King
2013-09-10 0:57 ` [PATCH v6 1/8] reset: rename update_refs to reset_refs Brad King
2013-09-10 3:43 ` Ramkumar Ramachandra
2013-09-10 0:57 ` [PATCH v6 2/8] refs: report ref type from lock_any_ref_for_update Brad King
2013-09-10 0:57 ` [PATCH v6 3/8] refs: factor update_ref steps into helpers Brad King
2013-09-10 0:57 ` [PATCH v6 4/8] refs: factor delete_ref loose ref step into a helper Brad King
2013-09-10 0:57 ` [PATCH v6 5/8] refs: add function to repack without multiple refs Brad King
2013-09-10 0:57 ` [PATCH v6 6/8] refs: add update_refs for multiple simultaneous updates Brad King
2013-09-10 0:57 ` [PATCH v6 7/8] update-ref: support " Brad King
2013-09-10 22:51 ` Eric Sunshine
2013-09-11 12:36 ` Brad King
2013-09-11 16:07 ` Eric Sunshine
2013-09-10 0:57 ` [PATCH v6 8/8] update-ref: add test cases covering --stdin signature Brad King
2013-09-10 22:46 ` Eric Sunshine
2013-09-10 22:54 ` Junio C Hamano
2013-09-11 12:46 ` [PATCH v6.1 " Brad King
2013-09-10 16:30 ` [PATCH v6 0/8] Multiple simultaneously locked ref updates Junio C Hamano
2013-09-10 16:54 ` Brad King
2013-09-10 20:18 ` Junio C Hamano
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