From: Jonathan Wakely <jwakely@redhat.com>
To: Rich Felker <dalias@libc.org>
Cc: "Florian Weimer" <fw@deneb.enyo.de>, Арсений <a@saur0n.science>,
musl@lists.openwall.com
Subject: Re: [musl] Mutexes are not unlocking
Date: Mon, 23 Nov 2020 17:10:16 +0000 [thread overview]
Message-ID: <20201123171016.GV1312820@redhat.com> (raw)
In-Reply-To: <20201123165121.GW534@brightrain.aerifal.cx>
On 23/11/20 11:51 -0500, Rich Felker wrote:
>On Mon, Nov 23, 2020 at 04:19:07PM +0000, Jonathan Wakely wrote:
>> On 23/11/20 09:53 -0500, Rich Felker wrote:
>> >On Mon, Nov 23, 2020 at 11:41:24AM +0000, Jonathan Wakely wrote:
>> >>If the musl libstdc++ removes the use of __gthread_active_p, but code
>> >>compiled against a glibc libstdc++ inlines the __gthread_active_p
>> >>check, then it seems to me that musl (or the musl libstdc++) needs to
>> >>ensure that the inlined __gthread_active_p will return true. It can do
>> >>that by providing a non-weak symbol called __pthread_key_create (the
>> >>symbol won't be called, it just has to exist).
>> >
>> >The target files for -musl tuples disable the hack entirely by adding
>> >t-gthr-noweak and -DGTHREAD_USE_WEAK=0 where appropriate. So there's
>> >no issue here. OP's problem was trying to make glibc-linked binaries
>> >and use them with musl's very limited glibc-ABI-compat capabilities,
>> >which is not recommended; it's only intended as an aid in running
>> >binaryware (esp shared libraries) you can't build/get native versions
>> >of.
>>
>> OK. If supporting that not recommended case does become desirable,
>> defining a __pthread_key_create symbol somewhere should work.
>>
>> Or users might be able to solve it for themselves by creating a tiny
>> shared library that contains nothing but a symbol called
>> __pthread_key_create and LD_PRELOADing that, so that the checks in the
>> binaryware looking for that symbol become true.
>
>My understanding was that only static linking was broken by the weak
>ref hack, so I'm not sure why it's happening to begin with. Is
>libstdc++ actually looking for __pthread_key_create rather than
>pthread_key_create?
Yes. I don't remember why but maybe pthread_key_create exists as a
stub in glibc's libc.so and so __pthread_key_create is used to
**really** detect that libpthread.so is linked in.
>That could explain it since we don't provide the
>former (and as responsibility for making this stuff work is shifted to
>gcompat, gcompat could provide it).
Ah, if you already have a library for glibc-compatibility then yes,
adding __pthread_key_create there would seem to make sense.
next prev parent reply other threads:[~2020-11-23 17:18 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-20 5:25 a
2020-11-20 5:58 ` Rich Felker
2020-11-21 6:46 ` Re[2]: " a
2020-11-21 15:51 ` Rich Felker
2020-11-22 18:43 ` Re[2]: " Арсений
2020-11-22 19:11 ` Rich Felker
2020-11-22 19:23 ` Florian Weimer
2020-11-22 19:28 ` Rich Felker
2020-11-22 19:45 ` Re[2]: " Арсений
2020-11-22 20:05 ` Арсений
2020-11-23 12:24 ` Jonathan Wakely
2020-11-23 14:56 ` Rich Felker
2020-11-23 16:58 ` Jonathan Wakely
2020-11-23 11:41 ` Jonathan Wakely
2020-11-23 14:53 ` Rich Felker
2020-11-23 16:19 ` Jonathan Wakely
2020-11-23 16:51 ` Rich Felker
2020-11-23 17:10 ` Jonathan Wakely [this message]
2020-11-23 17:18 ` Florian Weimer
2020-11-23 16:59 ` Florian Weimer
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
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20201123171016.GV1312820@redhat.com \
--to=jwakely@redhat.com \
--cc=a@saur0n.science \
--cc=dalias@libc.org \
--cc=fw@deneb.enyo.de \
--cc=musl@lists.openwall.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.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
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 NNTP newsgroup(s).