* [PATCH] libstdc++: Strengthen memory order for atomic<T>::wait/notify
@ 2022-02-09 17:35 Thomas Rodgers
2022-02-09 20:36 ` Jonathan Wakely
0 siblings, 1 reply; 3+ messages in thread
From: Thomas Rodgers @ 2022-02-09 17:35 UTC (permalink / raw)
To: libstdc++; +Cc: gcc Patches
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This patch changes the memory order used in the spin wait code to match
that of libc++.
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From 92caa08b272520ec4a272b302b37d8fb47afb2ab Mon Sep 17 00:00:00 2001
From: Thomas Rodgers <rodgert@appliantology.com>
Date: Wed, 9 Feb 2022 09:26:00 -0800
Subject: [PATCH] libstdc++: Strengthen memory order for atomic<T>::wait/notify
(spinning)
This patch changes the memory order used in the spin wait code to match
that of libc++.
libstdc++-v3/ChangeLog:
* includ/bits/atomic_wait.h (__waiter_base::_S_do_spin,
__waiter_base::_S_do_spin_v): Change memory order from relaxed
to acquire.
---
libstdc++-v3/include/bits/atomic_wait.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/libstdc++-v3/include/bits/atomic_wait.h b/libstdc++-v3/include/bits/atomic_wait.h
index 6ce7f9343cf..125b1cad886 100644
--- a/libstdc++-v3/include/bits/atomic_wait.h
+++ b/libstdc++-v3/include/bits/atomic_wait.h
@@ -332,7 +332,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
else
{
- __atomic_load(__addr, &__val, __ATOMIC_RELAXED);
+ __atomic_load(__addr, &__val, __ATOMIC_ACQUIRE);
}
return __atomic_spin(__pred, __spin);
}
@@ -353,7 +353,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__platform_wait_t& __val,
_Spin __spin = _Spin{ })
{
- __atomic_load(__addr, &__val, __ATOMIC_RELAXED);
+ __atomic_load(__addr, &__val, __ATOMIC_ACQUIRE);
return __atomic_spin(__pred, __spin);
}
--
2.34.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] libstdc++: Strengthen memory order for atomic<T>::wait/notify
2022-02-09 17:35 [PATCH] libstdc++: Strengthen memory order for atomic<T>::wait/notify Thomas Rodgers
@ 2022-02-09 20:36 ` Jonathan Wakely
2022-02-10 18:22 ` Thomas Rodgers
0 siblings, 1 reply; 3+ messages in thread
From: Jonathan Wakely @ 2022-02-09 20:36 UTC (permalink / raw)
To: Thomas Rodgers; +Cc: libstdc++, gcc Patches
On Wed, 9 Feb 2022 at 17:35, Thomas Rodgers via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
>
> This patch changes the memory order used in the spin wait code to match
> that of libc++.
OK for trunk (and gcc-11 if needed).
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] libstdc++: Strengthen memory order for atomic<T>::wait/notify
2022-02-09 20:36 ` Jonathan Wakely
@ 2022-02-10 18:22 ` Thomas Rodgers
0 siblings, 0 replies; 3+ messages in thread
From: Thomas Rodgers @ 2022-02-10 18:22 UTC (permalink / raw)
To: Jonathan Wakely; +Cc: libstdc++, gcc Patches
Committed to trunk, backported to gcc-11.
On Wed, Feb 9, 2022 at 12:37 PM Jonathan Wakely <jwakely@redhat.com> wrote:
> On Wed, 9 Feb 2022 at 17:35, Thomas Rodgers via Libstdc++
> <libstdc++@gcc.gnu.org> wrote:
> >
> > This patch changes the memory order used in the spin wait code to match
> > that of libc++.
>
> OK for trunk (and gcc-11 if needed).
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-02-09 17:35 [PATCH] libstdc++: Strengthen memory order for atomic<T>::wait/notify Thomas Rodgers
2022-02-09 20:36 ` Jonathan Wakely
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