Re: [PATCH] libstdc++: Fix wrong thread waking on notify [PR100334]

2021-05-17 Thread Thomas Rodgers 

On 2021-05-17 09:43, Jonathan Wakely wrote:

On 14/05/21 18:09 +0100, Jonathan Wakely wrote: On 13/05/21 18:54 
-0700, Thomas Rodgers wrote: From: Thomas Rodgers 



Please ignore the previous patch. This one removes the need to carry 
any

extra state in the case of a 'laundered' atomic wait.

libstdc++/ChangeLog:
* include/bits/atomic_wait.h (__waiter::_M_do_wait_v): loop
until value change observed.
(__waiter_base::_M_laundered): New member function.
(__watier_base::_M_notify): Check _M_laundered() to determine
whether to wake one or all.
(__detail::__atomic_compare): Return true if call to
__builtin_memcmp() == 0.
(__waiter_base::_S_do_spin_v): Adjust predicate.
* testsuite/29_atomics/atomic/wait_notify/100334.cc: New
test.
---
libstdc++-v3/include/bits/atomic_wait.h   | 28 --
.../29_atomics/atomic/wait_notify/100334.cc   | 94 +++
2 files changed, 114 insertions(+), 8 deletions(-)
create mode 100644 
libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/100334.cc


diff --git a/libstdc++-v3/include/bits/atomic_wait.h 
b/libstdc++-v3/include/bits/atomic_wait.h

index 984ed70f16c..07bb744d822 100644
--- a/libstdc++-v3/include/bits/atomic_wait.h
+++ b/libstdc++-v3/include/bits/atomic_wait.h
@@ -181,11 +181,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return false;
}

+// return true if equal
template
bool __atomic_compare(const _Tp& __a, const _Tp& __b)
{
// TODO make this do the correct padding bit ignoring comparison
-return __builtin_memcmp(&__a, &__b, sizeof(_Tp)) != 0;
+return __builtin_memcmp(&__a, &__b, sizeof(_Tp)) == 0;
}

struct __waiter_pool_base
@@ -300,14 +301,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
explicit __waiter_base(const _Up* __addr) noexcept
: _M_w(_S_for(__addr))
, _M_addr(_S_wait_addr(__addr, &_M_w._M_ver))
-  {
-  }
+  { }
+
+bool
+_M_laundered() const
+{ return _M_addr == &_M_w._M_ver; }

void
_M_notify(bool __all, bool __bare = false)
{
-  if (_M_addr == &_M_w._M_ver)
-__atomic_fetch_add(_M_addr, 1, __ATOMIC_ACQ_REL);
+  if (_M_laundered())
+{
+  __atomic_fetch_add(_M_addr, 1, __ATOMIC_ACQ_REL);
Please mention this increment in the changelog.


Ugh, sorry, I seem to have forgotten how to read a diff.


OK for trunk and gcc-11 with that change, thanks.


OK to push, no changes needed.

Tested x86_64-pc-linux-gnu, committed to master and cherry-picked to 
releases/gcc-11.

Re: [PATCH] libstdc++: Fix wrong thread waking on notify [PR100334]

2021-05-17 Thread Jonathan Wakely via Gcc-patches 

On 14/05/21 18:09 +0100, Jonathan Wakely wrote:

On 13/05/21 18:54 -0700, Thomas Rodgers wrote:

From: Thomas Rodgers 

Please ignore the previous patch. This one removes the need to carry any
extra state in the case of a 'laundered' atomic wait.

libstdc++/ChangeLog:
* include/bits/atomic_wait.h (__waiter::_M_do_wait_v): loop
until value change observed.
(__waiter_base::_M_laundered): New member function.
(__watier_base::_M_notify): Check _M_laundered() to determine
whether to wake one or all.
(__detail::__atomic_compare): Return true if call to
__builtin_memcmp() == 0.
(__waiter_base::_S_do_spin_v): Adjust predicate.
* testsuite/29_atomics/atomic/wait_notify/100334.cc: New
test.
---
libstdc++-v3/include/bits/atomic_wait.h   | 28 --
.../29_atomics/atomic/wait_notify/100334.cc   | 94 +++
2 files changed, 114 insertions(+), 8 deletions(-)
create mode 100644 
libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/100334.cc

diff --git a/libstdc++-v3/include/bits/atomic_wait.h 
b/libstdc++-v3/include/bits/atomic_wait.h
index 984ed70f16c..07bb744d822 100644
--- a/libstdc++-v3/include/bits/atomic_wait.h
+++ b/libstdc++-v3/include/bits/atomic_wait.h
@@ -181,11 +181,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return false;
 }

+// return true if equal
   template
 bool __atomic_compare(const _Tp& __a, const _Tp& __b)
 {
// TODO make this do the correct padding bit ignoring comparison
-   return __builtin_memcmp(&__a, &__b, sizeof(_Tp)) != 0;
+   return __builtin_memcmp(&__a, &__b, sizeof(_Tp)) == 0;
 }

   struct __waiter_pool_base
@@ -300,14 +301,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
  explicit __waiter_base(const _Up* __addr) noexcept
: _M_w(_S_for(__addr))
, _M_addr(_S_wait_addr(__addr, &_M_w._M_ver))
- {
- }
+ { }
+
+   bool
+   _M_laundered() const
+   { return _M_addr == &_M_w._M_ver; }

void
_M_notify(bool __all, bool __bare = false)
{
- if (_M_addr == &_M_w._M_ver)
-   __atomic_fetch_add(_M_addr, 1, __ATOMIC_ACQ_REL);
+ if (_M_laundered())
+   {
+ __atomic_fetch_add(_M_addr, 1, __ATOMIC_ACQ_REL);


Please mention this increment in the changelog.


Ugh, sorry, I seem to have forgotten how to read a diff.


OK for trunk and gcc-11 with that change, thanks.


OK to push, no changes needed.

Re: [PATCH] libstdc++: Fix wrong thread waking on notify [PR100334]

2021-05-14 Thread Jonathan Wakely via Gcc-patches 

On 13/05/21 18:54 -0700, Thomas Rodgers wrote:

From: Thomas Rodgers 

Please ignore the previous patch. This one removes the need to carry any
extra state in the case of a 'laundered' atomic wait.

libstdc++/ChangeLog:
* include/bits/atomic_wait.h (__waiter::_M_do_wait_v): loop
until value change observed.
(__waiter_base::_M_laundered): New member function.
(__watier_base::_M_notify): Check _M_laundered() to determine
whether to wake one or all.
(__detail::__atomic_compare): Return true if call to
__builtin_memcmp() == 0.
(__waiter_base::_S_do_spin_v): Adjust predicate.
* testsuite/29_atomics/atomic/wait_notify/100334.cc: New
test.
---
libstdc++-v3/include/bits/atomic_wait.h   | 28 --
.../29_atomics/atomic/wait_notify/100334.cc   | 94 +++
2 files changed, 114 insertions(+), 8 deletions(-)
create mode 100644 
libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/100334.cc

diff --git a/libstdc++-v3/include/bits/atomic_wait.h 
b/libstdc++-v3/include/bits/atomic_wait.h
index 984ed70f16c..07bb744d822 100644
--- a/libstdc++-v3/include/bits/atomic_wait.h
+++ b/libstdc++-v3/include/bits/atomic_wait.h
@@ -181,11 +181,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return false;
  }

+// return true if equal
template
  bool __atomic_compare(const _Tp& __a, const _Tp& __b)
  {
// TODO make this do the correct padding bit ignoring comparison
-   return __builtin_memcmp(&__a, &__b, sizeof(_Tp)) != 0;
+   return __builtin_memcmp(&__a, &__b, sizeof(_Tp)) == 0;
  }

struct __waiter_pool_base
@@ -300,14 +301,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
  explicit __waiter_base(const _Up* __addr) noexcept
: _M_w(_S_for(__addr))
, _M_addr(_S_wait_addr(__addr, &_M_w._M_ver))
- {
- }
+ { }
+
+   bool
+   _M_laundered() const
+   { return _M_addr == &_M_w._M_ver; }

void
_M_notify(bool __all, bool __bare = false)
{
- if (_M_addr == &_M_w._M_ver)
-   __atomic_fetch_add(_M_addr, 1, __ATOMIC_ACQ_REL);
+ if (_M_laundered())
+   {
+ __atomic_fetch_add(_M_addr, 1, __ATOMIC_ACQ_REL);


Please mention this increment in the changelog.

OK for trunk and gcc-11 with that change, thanks.

[PATCH] libstdc++: Fix wrong thread waking on notify [PR100334]

2021-05-13 Thread Thomas Rodgers 
From: Thomas Rodgers 

Please ignore the previous patch. This one removes the need to carry any
extra state in the case of a 'laundered' atomic wait.

libstdc++/ChangeLog:
* include/bits/atomic_wait.h (__waiter::_M_do_wait_v): loop
until value change observed.
(__waiter_base::_M_laundered): New member function.
(__watier_base::_M_notify): Check _M_laundered() to determine
whether to wake one or all.
(__detail::__atomic_compare): Return true if call to
__builtin_memcmp() == 0.
(__waiter_base::_S_do_spin_v): Adjust predicate.
* testsuite/29_atomics/atomic/wait_notify/100334.cc: New
test.
---
 libstdc++-v3/include/bits/atomic_wait.h   | 28 --
 .../29_atomics/atomic/wait_notify/100334.cc   | 94 +++
 2 files changed, 114 insertions(+), 8 deletions(-)
 create mode 100644 
libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/100334.cc

diff --git a/libstdc++-v3/include/bits/atomic_wait.h 
b/libstdc++-v3/include/bits/atomic_wait.h
index 984ed70f16c..07bb744d822 100644
--- a/libstdc++-v3/include/bits/atomic_wait.h
+++ b/libstdc++-v3/include/bits/atomic_wait.h
@@ -181,11 +181,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return false;
   }
 
+// return true if equal
 template
   bool __atomic_compare(const _Tp& __a, const _Tp& __b)
   {
// TODO make this do the correct padding bit ignoring comparison
-   return __builtin_memcmp(&__a, &__b, sizeof(_Tp)) != 0;
+   return __builtin_memcmp(&__a, &__b, sizeof(_Tp)) == 0;
   }
 
 struct __waiter_pool_base
@@ -300,14 +301,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
  explicit __waiter_base(const _Up* __addr) noexcept
: _M_w(_S_for(__addr))
, _M_addr(_S_wait_addr(__addr, &_M_w._M_ver))
- {
- }
+ { }
+
+   bool
+   _M_laundered() const
+   { return _M_addr == &_M_w._M_ver; }
 
void
_M_notify(bool __all, bool __bare = false)
{
- if (_M_addr == &_M_w._M_ver)
-   __atomic_fetch_add(_M_addr, 1, __ATOMIC_ACQ_REL);
+ if (_M_laundered())
+   {
+ __atomic_fetch_add(_M_addr, 1, __ATOMIC_ACQ_REL);
+ __all = true;
+   }
  _M_w._M_notify(_M_addr, __all, __bare);
}
 
@@ -320,7 +327,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   _Spin __spin = _Spin{ })
  {
auto const __pred = [=]
- { return __detail::__atomic_compare(__old, __vfn()); };
+ { return !__detail::__atomic_compare(__old, __vfn()); };
 
if constexpr (__platform_wait_uses_type<_Up>)
  {
@@ -387,7 +394,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__platform_wait_t __val;
if (__base_type::_M_do_spin_v(__old, __vfn, __val))
  return;
-   __base_type::_M_w._M_do_wait(__base_type::_M_addr, __val);
+
+   do
+ {
+   __base_type::_M_w._M_do_wait(__base_type::_M_addr, __val);
+ }
+   while (__detail::__atomic_compare(__old, __vfn()));
  }
 
template
@@ -452,7 +464,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 __atomic_notify_address(const _Tp* __addr, bool __all) noexcept
 {
   __detail::__bare_wait __w(__addr);
-  __w._M_notify(__all, true);
+  __w._M_notify(__all);
 }
 
   // This call is to be used by atomic types which track contention externally
diff --git a/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/100334.cc 
b/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/100334.cc
new file mode 100644
index 000..3e63eca42fa
--- /dev/null
+++ b/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/100334.cc
@@ -0,0 +1,94 @@
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-gthreads "" }
+// { dg-additional-options "-pthread" { target pthread } }
+// { dg-add-options libatomic }
+
+// Copyright (C) 2021 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// .
+
+#include 
+#include 
+
+#include 
+
+template 
+struct atomics_sharing_same_waiter
+{
+   std::atomic tmp[49 * 4] = {};
+   std::atomic* a[4] = {
+  { &tmp[0] },
+  { &tmp[16 * 4] },
+  { &tmp[32 * 4] },
+  { &tmp[48 * 4] }

[PATCH] libstdc++: Fix wrong thread waking on notify [PR100334]

2021-05-13 Thread Thomas Rodgers 
From: Thomas Rodgers 

libstdc++/ChangeLog:
* include/bits/atomic_wait.h (__waiter::_M_do_wait_v): loop
until value change observed.
(__waiter_base::_M_a): Renamed member from _M_addr, changed
type to uintptr_t.
(__waiter_base::_S_wait_addr): Change return type to uinptr_t,
sets LSB if 'laundering' the wait address 
(__waiter_base::_M_addr): New member, returns wait address,
masking off LSB of _M_a.
(__waiter_base::_M_laundered): New member, returns true if
LSB of _M_a is set.
(__waiter_base::_M_notify): Call _M_addr(), check _M_laundered()
to determine whether to wake one or all.
(__waiter_base::_M_do_spin_v): Call _M_addr().
(__waiter_base::_M_do_spin): Likewise.
(__waiter::_M_do_wait_v): Likewise.
(__waiter::_M_do_wait): Likewise.
(__detail::__atomic_compare): Return true if call to
__builtin_memcmp() == 0.
(__waiter_base::_S_do_spin_v): Adjust predicate.
* testsuite/29_atomics/atomic/wait_notify/100334.cc: New
test.
* include/bits/atomic_timed_wait.h
(__timed_waiter::_M_do_wait_until_v): Call _M_addr().
(__timed_waiter::_M_do_wait_until): Likewise.
---
 libstdc++-v3/include/bits/atomic_timed_wait.h |  6 +-
 libstdc++-v3/include/bits/atomic_wait.h   | 49 ++
 .../29_atomics/atomic/wait_notify/100334.cc   | 94 +++
 3 files changed, 129 insertions(+), 20 deletions(-)
 create mode 100644 
libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/100334.cc

diff --git a/libstdc++-v3/include/bits/atomic_timed_wait.h 
b/libstdc++-v3/include/bits/atomic_timed_wait.h
index ec7ff51cdbc..5fe64fa2219 100644
--- a/libstdc++-v3/include/bits/atomic_timed_wait.h
+++ b/libstdc++-v3/include/bits/atomic_timed_wait.h
@@ -289,7 +289,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
if (_M_do_spin(__old, std::move(__vfn), __val,
   __timed_backoff_spin_policy(__atime)))
  return true;
-   return __base_type::_M_w._M_do_wait_until(__base_type::_M_addr, 
__val, __atime);
+   return __base_type::_M_w._M_do_wait_until(__base_type::_M_addr(), 
__val, __atime);
  }
 
// returns true if wait ended before timeout
@@ -304,7 +304,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
  __now = _Clock::now())
  {
if (__base_type::_M_w._M_do_wait_until(
- __base_type::_M_addr, __val, __atime)
+ __base_type::_M_addr(), __val, __atime)
&& __pred())
  return true;
 
@@ -347,7 +347,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
auto __reltime = chrono::ceil<__wait_clock_t::duration>(__rtime);
 
return __base_type::_M_w._M_do_wait_until(
- __base_type::_M_addr,
+ __base_type::_M_addr(),
  __val,
  chrono::steady_clock::now() + 
__reltime);
  }
diff --git a/libstdc++-v3/include/bits/atomic_wait.h 
b/libstdc++-v3/include/bits/atomic_wait.h
index 984ed70f16c..06ebcc7bce3 100644
--- a/libstdc++-v3/include/bits/atomic_wait.h
+++ b/libstdc++-v3/include/bits/atomic_wait.h
@@ -181,11 +181,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return false;
   }
 
+// return true if equal
 template
   bool __atomic_compare(const _Tp& __a, const _Tp& __b)
   {
// TODO make this do the correct padding bit ignoring comparison
-   return __builtin_memcmp(&__a, &__b, sizeof(_Tp)) != 0;
+   return __builtin_memcmp(&__a, &__b, sizeof(_Tp)) == 0;
   }
 
 struct __waiter_pool_base
@@ -276,16 +277,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
using __waiter_type = _Tp;
 
__waiter_type& _M_w;
-   __platform_wait_t* _M_addr;
+   uintptr_t  _M_a;
 
template
- static __platform_wait_t*
+ static uintptr_t
  _S_wait_addr(const _Up* __a, __platform_wait_t* __b)
  {
if constexpr (__platform_wait_uses_type<_Up>)
- return 
reinterpret_cast<__platform_wait_t*>(const_cast<_Up*>(__a));
+ return reinterpret_cast(const_cast<_Up*>(__a));
else
- return __b;
+ return reinterpret_cast(__b) | 0x1;
  }
 
static __waiter_type&
@@ -299,16 +300,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template
  explicit __waiter_base(const _Up* __addr) noexcept
: _M_w(_S_for(__addr))
-   , _M_addr(_S_wait_addr(__addr, &_M_w._M_ver))
- {
- }
+   , _M_a(_S_wait_addr(__addr, &_M_w._M_ver))
+ { }
+
+   __platform_wait_t*
+   _M_addr() const noexcept
+   { return reinterpret_cast<__platform_wait_t*>(_M_a & (-1 << 1)); }
+
+   bool
+   _M_laundered() const
+   { return _M_a & 0x1;

Re: [PATCH] libstdc++: Fix wrong thread waking on notify [PR100334]

2021-05-10 Thread Jonathan Wakely via Gcc-patches 

On 03/05/21 09:43 -0700, Thomas Rodgers wrote:

From: Thomas Rodgers 

This should also be backported to gcc-11


The additional _M_laundered data member changes the object layout.
That isn't safe for the branch. Would it be possible to smuggle that
flag in the least significant bit of the _M_addr member, which is
always aligned to more than one byte? Just on the gcc-11 branch, not
for trunk.



libstdc++/ChangeLog:
* include/bits/atomic_wait.h (__waiter::_M_do_wait_v): loop
until observe value change.
(__waiter_base::_M_laundered): New member.
(__watier_base::_M_notify): Check _M_laundered to determine
whether to wake one or all.
(__detail::__atomic_compare): Do not implicitly convert
result of __buildtin_memcpmp to bool,


Typos, and the description doesn't seem accurate (it wasn't implicitly
converting it to bool, there was always an explicit comparison, but
now it's == rather than !=).


(__waiter_base::_S_do_spin_v): Adjust predicate.
* testsuite/29_atomics/atomic/wait_notify/100334.cc: New
test.



OK for trunk with a fixed changelog, but we need a different patch for
the branch.

[PATCH] libstdc++: Fix wrong thread waking on notify [PR100334]

2021-05-03 Thread Thomas Rodgers 
From: Thomas Rodgers 

This should also be backported to gcc-11

libstdc++/ChangeLog:
* include/bits/atomic_wait.h (__waiter::_M_do_wait_v): loop
until observe value change.
(__waiter_base::_M_laundered): New member.
(__watier_base::_M_notify): Check _M_laundered to determine
whether to wake one or all.
(__detail::__atomic_compare): Do not implicitly convert
result of __buildtin_memcpmp to bool,
(__waiter_base::_S_do_spin_v): Adjust predicate.
* testsuite/29_atomics/atomic/wait_notify/100334.cc: New
test.
---
 libstdc++-v3/include/bits/atomic_wait.h   | 20 +++-
 .../29_atomics/atomic/wait_notify/100334.cc   | 94 +++
 2 files changed, 109 insertions(+), 5 deletions(-)
 create mode 100644 
libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/100334.cc

diff --git a/libstdc++-v3/include/bits/atomic_wait.h 
b/libstdc++-v3/include/bits/atomic_wait.h
index 984ed70f16c..528e4868410 100644
--- a/libstdc++-v3/include/bits/atomic_wait.h
+++ b/libstdc++-v3/include/bits/atomic_wait.h
@@ -181,11 +181,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return false;
   }
 
+// return true if equal
 template
   bool __atomic_compare(const _Tp& __a, const _Tp& __b)
   {
// TODO make this do the correct padding bit ignoring comparison
-   return __builtin_memcmp(&__a, &__b, sizeof(_Tp)) != 0;
+   return __builtin_memcmp(&__a, &__b, sizeof(_Tp)) == 0;
   }
 
 struct __waiter_pool_base
@@ -277,6 +278,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
__waiter_type& _M_w;
__platform_wait_t* _M_addr;
+   bool _M_laundered;
 
template
  static __platform_wait_t*
@@ -300,6 +302,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
  explicit __waiter_base(const _Up* __addr) noexcept
: _M_w(_S_for(__addr))
, _M_addr(_S_wait_addr(__addr, &_M_w._M_ver))
+   , _M_laundered(!__platform_wait_uses_type<_Up>)
  {
  }
 
@@ -308,7 +311,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
  if (_M_addr == &_M_w._M_ver)
__atomic_fetch_add(_M_addr, 1, __ATOMIC_ACQ_REL);
- _M_w._M_notify(_M_addr, __all, __bare);
+ _M_w._M_notify(_M_addr,
+(_M_laundered ? true : __all),
+__bare);
}
 
template)
  {
@@ -387,7 +392,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__platform_wait_t __val;
if (__base_type::_M_do_spin_v(__old, __vfn, __val))
  return;
-   __base_type::_M_w._M_do_wait(__base_type::_M_addr, __val);
+
+   do
+ {
+   __base_type::_M_w._M_do_wait(__base_type::_M_addr, __val);
+ }
+   while (__detail::__atomic_compare(__old, __vfn()));
  }
 
template
@@ -452,7 +462,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 __atomic_notify_address(const _Tp* __addr, bool __all) noexcept
 {
   __detail::__bare_wait __w(__addr);
-  __w._M_notify(__all, true);
+  __w._M_notify(__all);
 }
 
   // This call is to be used by atomic types which track contention externally
diff --git a/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/100334.cc 
b/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/100334.cc
new file mode 100644
index 000..3e63eca42fa
--- /dev/null
+++ b/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/100334.cc
@@ -0,0 +1,94 @@
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-gthreads "" }
+// { dg-additional-options "-pthread" { target pthread } }
+// { dg-add-options libatomic }
+
+// Copyright (C) 2021 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// .
+
+#include 
+#include 
+
+#include 
+
+template 
+struct atomics_sharing_same_waiter
+{
+   std::atomic tmp[49 * 4] = {};
+   std::atomic* a[4] = {
+  { &tmp[0] },
+  { &tmp[16 * 4] },
+  { &tmp[32 * 4] },
+  { &tmp[48 * 4] }
+   };
+};
+
+constexpr unsigned key(void * a)
+{
+  constexpr uintptr_t ct = 16;
+  return (uintptr_t(a) >> 2) % ct;
+}
+
+int
+main()
+{
+  // all atomic share the same waiter
+//  atomics_sharing_same_waiter atomics;
+  atomics_sharing_same_waiter atomics;
+  for (auto& atom : atomics.a)
+