From: Jason Merrill <jason@redhat.com>
To: Bernd Edlinger <bernd.edlinger@hotmail.de>,
"Richard Earnshaw (lists)" <Richard.Earnshaw@arm.com>,
"gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>,
Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>,
Nathan Sidwell <nathan@acm.org>,
Christophe Lyon <christophe.lyon@linaro.org>
Subject: Re: [PATCH] Avoid atomic for guard acquire when that is expensive
Date: Tue, 24 Nov 2020 17:10:13 -0500 [thread overview]
Message-ID: <37023468-e7b3-0c38-265d-1065637e953e@redhat.com> (raw)
In-Reply-To: <AM6PR03MB517068C1808B39346FDC2728E4FD0@AM6PR03MB5170.eurprd03.prod.outlook.com>
On 11/22/20 3:05 AM, Bernd Edlinger wrote:
> Hi,
>
> this avoids the need to use -fno-threadsafe-statics on
> arm-none-eabi or working around that problem by supplying
> a dummy __sync_synchronize function which might
> just lead to silent code failure of the worst kind
> (non-reproducable, racy) at runtime, as was pointed out
> on previous discussions here.
>
> When the atomic access involves a call to __sync_synchronize
> it is better to call __cxa_guard_acquire unconditionally,
> since it handles the atomics too, or is a non-threaded
> implementation when there is no gthread support for this target.
>
> This fixes also a bug for the ARM EABI big-endian target,
> that is, previously the wrong bit was checked.
Instead of a new target macro, can't you follow
fold_builtin_atomic_always_lock_free/can_atomic_load_p?
Jason
next prev parent reply other threads:[~2020-11-24 22:10 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-03 15:08 [PATCH] libgcc: Add a weak stub for __sync_synchronize Bernd Edlinger
2020-11-17 5:43 ` [PING] " Bernd Edlinger
2020-11-17 12:44 ` Richard Earnshaw (lists)
2020-11-17 15:18 ` Bernd Edlinger
2020-11-17 15:41 ` Richard Earnshaw (lists)
2020-11-17 15:51 ` Christophe Lyon
2020-11-17 17:17 ` Bernd Edlinger
2020-11-22 8:05 ` [PATCH] Avoid atomic for guard acquire when that is expensive Bernd Edlinger
2020-11-24 22:10 ` Jason Merrill [this message]
2020-12-01 18:28 ` Bernd Edlinger
2020-12-02 18:57 ` Jason Merrill
2020-12-05 12:37 ` Bernd Edlinger
2020-12-07 15:04 ` Jason Merrill
2020-12-07 16:17 ` Bernd Edlinger
2020-12-08 19:50 ` Jason Merrill
2020-11-30 20:08 ` [PING] " Bernd Edlinger
2020-11-30 20:54 ` Jason Merrill
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=37023468-e7b3-0c38-265d-1065637e953e@redhat.com \
--to=jason@redhat.com \
--cc=Richard.Earnshaw@arm.com \
--cc=bernd.edlinger@hotmail.de \
--cc=christophe.lyon@linaro.org \
--cc=gcc-patches@gcc.gnu.org \
--cc=nathan@acm.org \
--cc=ramana.radhakrishnan@arm.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).