* Re: [PATCH] clear_child_for_cleanup must correctly manage children_to_clean
2012-09-11 14:32 ` [PATCH] clear_child_for_cleanup must correctly manage children_to_clean David Gould
@ 2012-09-11 15:20 ` Jeff King
2012-09-11 17:32 ` Junio C Hamano
2012-09-11 15:30 ` Erik Faye-Lund
2012-09-11 20:22 ` [PATCHv2] fix broken list iteration in clear_child_for_cleanup David Gould
2 siblings, 1 reply; 6+ messages in thread
From: Jeff King @ 2012-09-11 15:20 UTC (permalink / raw)
To: David Gould; +Cc: git, gitster, kusmabite
On Tue, Sep 11, 2012 at 03:32:47PM +0100, David Gould wrote:
> Subject: Re: [PATCH] clear_child_for_cleanup must correctly manage
> children_to_clean
Thanks for the patch. Overall it looks good, but let me nit-pick your
commit message a little (not because it is that horrible, but because
you are so close to perfect that I want to fix the minor things and then
encourage you to submit more patches :) ).
Your subject is a bit vague, and it is not clear if it is not correct
now, and this is a bugfix, or if it is a feature enhancement. I would
have said something like:
Subject: fix broken list iteration in clear_child_for_cleanup
which is _also_ vague about what exactly the breakage is, but is clear
that this is a bugfix. So then you can go on to describe the actual
problem:
We iterate through the list of children to cleanup, but do not keep
our "last" pointer up to date. As a result, we may end up cutting off
part of the list instead of removing a single element.
And then describe your fix:
> Iterate through children_to_clean using 'next' fields but with an
> extra level of indirection. This allows us to update the chain when
> we remove a child and saves us managing several variables around
> the loop mechanism.
which I think is good.
> - last = &children_to_clean;
> - for (p = children_to_clean; p; p = p->next) {
> - if (p->pid == pid) {
> - *last = p->next;
> - free(p);
> + for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
> + if ((*pp)->pid == pid) {
> + struct child_to_clean *clean_me = *pp;
> + *pp = clean_me->next;
> + free(clean_me);
> return;
> }
I think using the indirect pointer is a nice compromise; it makes it
clear from just the for loop that this is not an ordinary for-each
traversal. You could hoist the extra pointer out of the conditional and
save one set of parentheses in the "if" statement, but I don't think it
is a big deal either way.
Acked-by: Jeff King <peff@peff.net>
Thanks for the bug report and the patch.
-Peff
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] clear_child_for_cleanup must correctly manage children_to_clean
2012-09-11 15:20 ` Jeff King
@ 2012-09-11 17:32 ` Junio C Hamano
0 siblings, 0 replies; 6+ messages in thread
From: Junio C Hamano @ 2012-09-11 17:32 UTC (permalink / raw)
To: Jeff King; +Cc: David Gould, git, kusmabite
Jeff King <peff@peff.net> writes:
> Thanks for the patch. Overall it looks good, but let me nit-pick your
> commit message a little (not because it is that horrible, but because
> you are so close to perfect that I want to fix the minor things and then
> encourage you to submit more patches :) ).
> ...
>
> Acked-by: Jeff King <peff@peff.net>
Thanks, both. I'd have to ask for a Sign-off, though.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] clear_child_for_cleanup must correctly manage children_to_clean
2012-09-11 14:32 ` [PATCH] clear_child_for_cleanup must correctly manage children_to_clean David Gould
2012-09-11 15:20 ` Jeff King
@ 2012-09-11 15:30 ` Erik Faye-Lund
2012-09-11 20:22 ` [PATCHv2] fix broken list iteration in clear_child_for_cleanup David Gould
2 siblings, 0 replies; 6+ messages in thread
From: Erik Faye-Lund @ 2012-09-11 15:30 UTC (permalink / raw)
To: David Gould; +Cc: git, gitster, peff
On Tue, Sep 11, 2012 at 4:32 PM, David Gould <david@optimisefitness.com> wrote:
> Iterate through children_to_clean using 'next' fields but with an
> extra level of indirection. This allows us to update the chain when
> we remove a child and saves us managing several variables around
> the loop mechanism.
> ---
> run-command.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/run-command.c b/run-command.c
> index f9922b9..c42d63b 100644
> --- a/run-command.c
> +++ b/run-command.c
> @@ -53,13 +53,13 @@ static void mark_child_for_cleanup(pid_t pid)
>
> static void clear_child_for_cleanup(pid_t pid)
> {
> - struct child_to_clean **last, *p;
> + struct child_to_clean **pp;
>
> - last = &children_to_clean;
> - for (p = children_to_clean; p; p = p->next) {
> - if (p->pid == pid) {
> - *last = p->next;
> - free(p);
> + for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
> + if ((*pp)->pid == pid) {
> + struct child_to_clean *clean_me = *pp;
> + *pp = clean_me->next;
> + free(clean_me);
> return;
> }
> }
> --
> 1.7.9.5
>
Looks good to me. Thanks :)
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCHv2] fix broken list iteration in clear_child_for_cleanup
2012-09-11 14:32 ` [PATCH] clear_child_for_cleanup must correctly manage children_to_clean David Gould
2012-09-11 15:20 ` Jeff King
2012-09-11 15:30 ` Erik Faye-Lund
@ 2012-09-11 20:22 ` David Gould
2012-09-11 20:32 ` Junio C Hamano
2 siblings, 1 reply; 6+ messages in thread
From: David Gould @ 2012-09-11 20:22 UTC (permalink / raw)
To: git, gitster, peff, kusmabite; +Cc: David Gould
We iterate through the list of children to cleanup, but do not keep
our "last" pointer up to date. As a result, we may end up cutting off
part of the list instead of removing a single element.
Iterate through children_to_clean using 'next' fields but with an
extra level of indirection. This allows us to update the chain when
we remove a child and saves us managing several variables around
the loop mechanism.
Signed-off-by: David Gould <david@optimisefitness.com>
Acked-by: Jeff King <peff@peff.net>
---
PATCHv2 updates PATCH only in the commit message: Peff suggested
both a helpful subject and a more-informative introduction.
run-command.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/run-command.c b/run-command.c
index f9922b9..c42d63b 100644
--- a/run-command.c
+++ b/run-command.c
@@ -53,13 +53,13 @@ static void mark_child_for_cleanup(pid_t pid)
static void clear_child_for_cleanup(pid_t pid)
{
- struct child_to_clean **last, *p;
+ struct child_to_clean **pp;
- last = &children_to_clean;
- for (p = children_to_clean; p; p = p->next) {
- if (p->pid == pid) {
- *last = p->next;
- free(p);
+ for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
+ if ((*pp)->pid == pid) {
+ struct child_to_clean *clean_me = *pp;
+ *pp = clean_me->next;
+ free(clean_me);
return;
}
}
--
1.7.9.5
^ permalink raw reply related [flat|nested] 6+ messages in thread