From: Bart Schaefer <schaefer@brasslantern.com>
To: Roman Perepelitsa <roman.perepelitsa@gmail.com>
Cc: "zsh-workers@zsh.org" <zsh-workers@zsh.org>
Subject: Re: [patch] Avoid race in zf_mkdir
Date: Fri, 9 Oct 2020 13:47:49 -0700 [thread overview]
Message-ID: <CAH+w=7ZRvW3Yq3XO6TwbK1hgSDNE8ynX0eQOU2dTuLcAELNUDg@mail.gmail.com> (raw)
In-Reply-To: <CAN=4vMoJrD+g4Go37yT6gF-Lx61vHm45GvmG1Fx6-+3yyb1hAQ@mail.gmail.com>
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On Fri, Oct 9, 2020 at 1:35 PM Roman Perepelitsa <
roman.perepelitsa@gmail.com> wrote:
> On Fri, Oct 9, 2020 at 10:25 PM Bart Schaefer <schaefer@brasslantern.com>
> wrote:
> >
> > Er, sorry, this doesn't actually avoid the race, it just prevents the
> error message from being shown by whichever shell loses the race.
>
> I think this is the expected behavior. It's prescribed by POSIX for mkdir.
>
[...]
>
> The patch is incorrect for a different reason. If `zf_mkdir -p foo` is
> racing with another process that's doing `mkdir foo && rmdir foo`, the
> zf_mkdir call must never fail but with this patch it can fail.
>
Hm ... in that case the code shouldn't call stat() unless the mkdir() gives
EEXIST? And then ignore ENOENT from stat()?
What if another process is doing "touch foo && rm foo"? How is it possible
to distinguish that from mkdir+rmdir ?
Or are we confusing the requirements for mkdir(2) from those for mkdir(1)
? I don't have the spec handy.
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next prev parent reply other threads:[~2020-10-09 20:48 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-09 20:07 Matthew Martin
2020-10-09 20:24 ` Bart Schaefer
2020-10-09 20:35 ` Roman Perepelitsa
2020-10-09 20:47 ` Bart Schaefer [this message]
2020-10-09 20:53 ` Matthew Martin
2020-10-09 21:22 ` Roman Perepelitsa
2020-10-09 21:27 ` Bart Schaefer
2020-10-10 11:50 ` Roman Perepelitsa
2020-10-15 10:01 ` Roman Perepelitsa
2020-10-15 15:29 ` Bart Schaefer
2020-10-15 15:36 ` Roman Perepelitsa
2020-10-15 16:47 ` Bart Schaefer
2020-10-22 13:30 ` Roman Perepelitsa
2020-10-09 21:40 ` Matthew Martin
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