From: Florian Weimer via Libc-alpha <libc-alpha@sourceware.org>
To: Rich Felker <dalias@libc.org>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH 2/2] manual: Document __libc_single_threaded
Date: Mon, 25 May 2020 10:08:37 +0200 [thread overview]
Message-ID: <87r1v8zbay.fsf@oldenburg2.str.redhat.com> (raw)
In-Reply-To: <20200523160202.GG1079@brightrain.aerifal.cx> (Rich Felker's message of "Sat, 23 May 2020 12:02:03 -0400")
* Rich Felker:
>> this can allow earlier single threaded detection than only
>> considering pthread_join: e.g. stdio, malloc etc may do a
>> check and update the global after an acquire barrier, however
>> the compiler must not cache globals across libc calls for this
>> to work.
>
> It can't cache globals across non-pure functions whose definitions it
> cant't see (and if it saw the definition it would know the global is
> modified).
All
> malloc is something of a special case where clang treats it
> not as a function but having "pure malloc semantics", but even then I
> don't think it matters if it caches it; at worst you see the old value
> of __libc_single_threaded (false) rather than the new one (true) and
> that direction is safe.
>
> Rich
next prev parent reply other threads:[~2020-05-25 8:08 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-20 18:12 [PATCH 0/2] Add __libc_single_threaded Florian Weimer via Libc-alpha
2020-05-20 18:12 ` [PATCH 1/2] Add the __libc_single_threaded variable Florian Weimer via Libc-alpha
2020-05-21 13:07 ` Szabolcs Nagy
2020-05-21 13:16 ` Florian Weimer via Libc-alpha
2020-05-21 13:26 ` Szabolcs Nagy
2020-05-20 18:12 ` [PATCH 2/2] manual: Document __libc_single_threaded Florian Weimer via Libc-alpha
2020-05-21 7:52 ` Michael Kerrisk (man-pages) via Libc-alpha
2020-05-21 12:17 ` Florian Weimer via Libc-alpha
2020-05-21 11:18 ` Szabolcs Nagy
2020-05-21 12:16 ` Florian Weimer via Libc-alpha
2020-05-21 12:50 ` Adhemerval Zanella via Libc-alpha
2020-05-21 13:09 ` Szabolcs Nagy
2020-05-21 13:15 ` Adhemerval Zanella via Libc-alpha
2020-05-21 13:30 ` Szabolcs Nagy
2020-05-21 13:44 ` Florian Weimer via Libc-alpha
2020-05-21 13:58 ` Adhemerval Zanella via Libc-alpha
2020-05-21 14:03 ` Florian Weimer via Libc-alpha
2020-05-22 10:01 ` Szabolcs Nagy
2020-05-22 10:05 ` Florian Weimer via Libc-alpha
2020-05-22 10:54 ` Szabolcs Nagy
2020-05-22 11:08 ` Florian Weimer via Libc-alpha
2020-05-22 15:07 ` Rich Felker
2020-05-22 16:14 ` Rich Felker
2020-05-22 16:36 ` Adhemerval Zanella via Libc-alpha
2020-05-22 17:02 ` Florian Weimer via Libc-alpha
2020-05-22 17:18 ` Florian Weimer via Libc-alpha
2020-05-22 17:28 ` Rich Felker
2020-05-22 17:40 ` Florian Weimer via Libc-alpha
2020-05-22 17:49 ` Rich Felker
2020-05-22 19:22 ` Szabolcs Nagy
2020-05-22 19:53 ` Rich Felker
2020-05-23 6:49 ` Szabolcs Nagy
2020-05-23 16:02 ` Rich Felker
2020-05-25 8:08 ` Florian Weimer via Libc-alpha
2020-05-25 17:21 ` Rich Felker
2020-05-27 11:54 ` Florian Weimer via Libc-alpha
2020-05-27 15:36 ` Rich Felker
2020-06-03 15:00 ` Florian Weimer via Libc-alpha
2020-06-03 17:11 ` Rich Felker
2020-05-25 8:08 ` Florian Weimer via Libc-alpha [this message]
2020-05-21 13:56 ` Adhemerval Zanella via Libc-alpha
2020-05-21 13:14 ` Florian Weimer via Libc-alpha
2020-05-21 14:32 ` Adhemerval Zanella via Libc-alpha
2020-06-03 15:48 ` Florian Weimer via Libc-alpha
2020-06-03 17:52 ` Adhemerval Zanella via Libc-alpha
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://www.gnu.org/software/libc/involved.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87r1v8zbay.fsf@oldenburg2.str.redhat.com \
--to=libc-alpha@sourceware.org \
--cc=dalias@libc.org \
--cc=fweimer@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).