[committed] libstdc++: Add TSan annotations to std::atomic<shared_ptr<T>>
Commit Message
Tested powerpc64le-linux, pushed to trunk.
-- >8 --
This adds annotations to std::atomic<shared_ptr<T>> to enable TSan to
understand the custom locking. Without this, TSan reports data races for
accesses to the _M_ptr member, even though those are correctly
synchronized using atomic operations on the tagged pointer.
libstdc++-v3/ChangeLog:
* include/bits/shared_ptr_atomic.h (_GLIBCXX_TSAN_MUTEX_DESTROY)
(_GLIBCXX_TSAN_MUTEX_PRE_LOCK, _GLIBCXX_TSAN_MUTEX_POST_LOCK)
(_GLIBCXX_TSAN_MUTEX_PRE_UNLOCK, _GLIBCXX_TSAN_MUTEX_POST_UNLOCK)
(_GLIBCXX_TSAN_MUTEX_PRE_SIGNAL, _GLIBCXX_TSAN_MUTEX_POST_SIGNAL):
Define macros for TSan annotation functions.
(_Sp_atomic::_Atomic_count): Add annotations.
---
libstdc++-v3/include/bits/shared_ptr_atomic.h | 38 +++++++++++++++++++
1 file changed, 38 insertions(+)
Comments
On Wed, 14 Sept 2022 at 23:05, Jonathan Wakely via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
>
> Tested powerpc64le-linux, pushed to trunk.
>
> -- >8 --
>
> This adds annotations to std::atomic<shared_ptr<T>> to enable TSan to
> understand the custom locking. Without this, TSan reports data races for
> accesses to the _M_ptr member, even though those are correctly
> synchronized using atomic operations on the tagged pointer.
>
> libstdc++-v3/ChangeLog:
>
> * include/bits/shared_ptr_atomic.h (_GLIBCXX_TSAN_MUTEX_DESTROY)
> (_GLIBCXX_TSAN_MUTEX_PRE_LOCK, _GLIBCXX_TSAN_MUTEX_POST_LOCK)
> (_GLIBCXX_TSAN_MUTEX_PRE_UNLOCK, _GLIBCXX_TSAN_MUTEX_POST_UNLOCK)
> (_GLIBCXX_TSAN_MUTEX_PRE_SIGNAL, _GLIBCXX_TSAN_MUTEX_POST_SIGNAL):
> Define macros for TSan annotation functions.
> (_Sp_atomic::_Atomic_count): Add annotations.
> ---
> libstdc++-v3/include/bits/shared_ptr_atomic.h | 38 +++++++++++++++++++
> 1 file changed, 38 insertions(+)
>
> diff --git a/libstdc++-v3/include/bits/shared_ptr_atomic.h b/libstdc++-v3/include/bits/shared_ptr_atomic.h
> index d4bd712fc7d..4580807f42c 100644
> --- a/libstdc++-v3/include/bits/shared_ptr_atomic.h
> +++ b/libstdc++-v3/include/bits/shared_ptr_atomic.h
> @@ -32,6 +32,30 @@
>
> #include <bits/atomic_base.h>
>
> +#if defined _GLIBCXX_TSAN && __has_include(<sanitizer/tsan_interface.h>)
> +#include <sanitizer/tsan_interface.h>
> +#define _GLIBCXX_TSAN_MUTEX_DESTROY(X) \
> + __tsan_mutex_destroy(X, __tsan_mutex_not_static)
> +#define _GLIBCXX_TSAN_MUTEX_PRE_LOCK(X) \
> + __tsan_mutex_pre_lock(X, __tsan_mutex_not_static)
> +#define _GLIBCXX_TSAN_MUTEX_POST_LOCK(X) \
> + __tsan_mutex_post_lock(X, __tsan_mutex_not_static, 0)
> +#define _GLIBCXX_TSAN_MUTEX_PRE_UNLOCK(X) \
> + __tsan_mutex_pre_unlock(X, __tsan_mutex_not_static)
> +#define _GLIBCXX_TSAN_MUTEX_POST_UNLOCK(X) \
> + __tsan_mutex_post_unlock(X, __tsan_mutex_not_static)
> +#define _GLIBCXX_TSAN_MUTEX_PRE_SIGNAL(X) __tsan_mutex_pre_signal(X, 0)
> +#define _GLIBCXX_TSAN_MUTEX_POST_SIGNAL(X) __tsan_mutex_post_signal(X, 0)
> +#else
> +#define _GLIBCXX_TSAN_MUTEX_DESTROY(X)
> +#define _GLIBCXX_TSAN_MUTEX_PRE_LOCK(X)
> +#define _GLIBCXX_TSAN_MUTEX_POST_LOCK(X)
> +#define _GLIBCXX_TSAN_MUTEX_PRE_UNLOCK(X)
> +#define _GLIBCXX_TSAN_MUTEX_POST_UNLOCK(X)
> +#define _GLIBCXX_TSAN_MUTEX_PRE_SIGNAL(X)
> +#define _GLIBCXX_TSAN_MUTEX_POST_SIGNAL(X)
> +#endif
> +
> namespace std _GLIBCXX_VISIBILITY(default)
> {
> _GLIBCXX_BEGIN_NAMESPACE_VERSION
> @@ -377,6 +401,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> ~_Atomic_count()
> {
> auto __val = _M_val.load(memory_order_relaxed);
> + _GLIBCXX_TSAN_MUTEX_DESTROY(&_M_val);
After further thought, I'm not sure this is right. This tells tsan
that the "mutex" at &_M_val cannot be locked or unlocked again after
this. But what happens if the address is reused by a different
atomic<shared_ptr<T>> which happens to be at the same memory address?
Will tsan think that's an invalid use of the original "mutex" after
its destruction?
I will investigate.
We might need to stop using the __tsan_mutex_destroy call, and if so,
we can stop using the __tsan_mutex_not_static flag too. The pre/post
lock/unlock/signal pairs are still valuable without the lifetime
checking.
On Wed, 14 Sept 2022 at 23:25, Jonathan Wakely wrote:
>
> On Wed, 14 Sept 2022 at 23:05, Jonathan Wakely via Libstdc++
> <libstdc++@gcc.gnu.org> wrote:
> >
> > Tested powerpc64le-linux, pushed to trunk.
> >
> > -- >8 --
> >
> > This adds annotations to std::atomic<shared_ptr<T>> to enable TSan to
> > understand the custom locking. Without this, TSan reports data races for
> > accesses to the _M_ptr member, even though those are correctly
> > synchronized using atomic operations on the tagged pointer.
> >
> > libstdc++-v3/ChangeLog:
> >
> > * include/bits/shared_ptr_atomic.h (_GLIBCXX_TSAN_MUTEX_DESTROY)
> > (_GLIBCXX_TSAN_MUTEX_PRE_LOCK, _GLIBCXX_TSAN_MUTEX_POST_LOCK)
> > (_GLIBCXX_TSAN_MUTEX_PRE_UNLOCK, _GLIBCXX_TSAN_MUTEX_POST_UNLOCK)
> > (_GLIBCXX_TSAN_MUTEX_PRE_SIGNAL, _GLIBCXX_TSAN_MUTEX_POST_SIGNAL):
> > Define macros for TSan annotation functions.
> > (_Sp_atomic::_Atomic_count): Add annotations.
> > ---
> > libstdc++-v3/include/bits/shared_ptr_atomic.h | 38 +++++++++++++++++++
> > 1 file changed, 38 insertions(+)
> >
> > diff --git a/libstdc++-v3/include/bits/shared_ptr_atomic.h b/libstdc++-v3/include/bits/shared_ptr_atomic.h
> > index d4bd712fc7d..4580807f42c 100644
> > --- a/libstdc++-v3/include/bits/shared_ptr_atomic.h
> > +++ b/libstdc++-v3/include/bits/shared_ptr_atomic.h
> > @@ -32,6 +32,30 @@
> >
> > #include <bits/atomic_base.h>
> >
> > +#if defined _GLIBCXX_TSAN && __has_include(<sanitizer/tsan_interface.h>)
> > +#include <sanitizer/tsan_interface.h>
> > +#define _GLIBCXX_TSAN_MUTEX_DESTROY(X) \
> > + __tsan_mutex_destroy(X, __tsan_mutex_not_static)
> > +#define _GLIBCXX_TSAN_MUTEX_PRE_LOCK(X) \
> > + __tsan_mutex_pre_lock(X, __tsan_mutex_not_static)
> > +#define _GLIBCXX_TSAN_MUTEX_POST_LOCK(X) \
> > + __tsan_mutex_post_lock(X, __tsan_mutex_not_static, 0)
> > +#define _GLIBCXX_TSAN_MUTEX_PRE_UNLOCK(X) \
> > + __tsan_mutex_pre_unlock(X, __tsan_mutex_not_static)
> > +#define _GLIBCXX_TSAN_MUTEX_POST_UNLOCK(X) \
> > + __tsan_mutex_post_unlock(X, __tsan_mutex_not_static)
> > +#define _GLIBCXX_TSAN_MUTEX_PRE_SIGNAL(X) __tsan_mutex_pre_signal(X, 0)
> > +#define _GLIBCXX_TSAN_MUTEX_POST_SIGNAL(X) __tsan_mutex_post_signal(X, 0)
> > +#else
> > +#define _GLIBCXX_TSAN_MUTEX_DESTROY(X)
> > +#define _GLIBCXX_TSAN_MUTEX_PRE_LOCK(X)
> > +#define _GLIBCXX_TSAN_MUTEX_POST_LOCK(X)
> > +#define _GLIBCXX_TSAN_MUTEX_PRE_UNLOCK(X)
> > +#define _GLIBCXX_TSAN_MUTEX_POST_UNLOCK(X)
> > +#define _GLIBCXX_TSAN_MUTEX_PRE_SIGNAL(X)
> > +#define _GLIBCXX_TSAN_MUTEX_POST_SIGNAL(X)
> > +#endif
> > +
> > namespace std _GLIBCXX_VISIBILITY(default)
> > {
> > _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > @@ -377,6 +401,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > ~_Atomic_count()
> > {
> > auto __val = _M_val.load(memory_order_relaxed);
> > + _GLIBCXX_TSAN_MUTEX_DESTROY(&_M_val);
>
> After further thought, I'm not sure this is right. This tells tsan
> that the "mutex" at &_M_val cannot be locked or unlocked again after
> this. But what happens if the address is reused by a different
> atomic<shared_ptr<T>> which happens to be at the same memory address?
> Will tsan think that's an invalid use of the original "mutex" after
> its destruction?
We can't easily add a call to __tsan_mutex_create, which would begin
the lifetime of a new object at that address, because the default
constructor is constexpr, and the create function isn't.
>
> I will investigate.
>
> We might need to stop using the __tsan_mutex_destroy call, and if so,
> we can stop using the __tsan_mutex_not_static flag too. The pre/post
> lock/unlock/signal pairs are still valuable without the lifetime
> checking.
@@ -32,6 +32,30 @@
#include <bits/atomic_base.h>
+#if defined _GLIBCXX_TSAN && __has_include(<sanitizer/tsan_interface.h>)
+#include <sanitizer/tsan_interface.h>
+#define _GLIBCXX_TSAN_MUTEX_DESTROY(X) \
+ __tsan_mutex_destroy(X, __tsan_mutex_not_static)
+#define _GLIBCXX_TSAN_MUTEX_PRE_LOCK(X) \
+ __tsan_mutex_pre_lock(X, __tsan_mutex_not_static)
+#define _GLIBCXX_TSAN_MUTEX_POST_LOCK(X) \
+ __tsan_mutex_post_lock(X, __tsan_mutex_not_static, 0)
+#define _GLIBCXX_TSAN_MUTEX_PRE_UNLOCK(X) \
+ __tsan_mutex_pre_unlock(X, __tsan_mutex_not_static)
+#define _GLIBCXX_TSAN_MUTEX_POST_UNLOCK(X) \
+ __tsan_mutex_post_unlock(X, __tsan_mutex_not_static)
+#define _GLIBCXX_TSAN_MUTEX_PRE_SIGNAL(X) __tsan_mutex_pre_signal(X, 0)
+#define _GLIBCXX_TSAN_MUTEX_POST_SIGNAL(X) __tsan_mutex_post_signal(X, 0)
+#else
+#define _GLIBCXX_TSAN_MUTEX_DESTROY(X)
+#define _GLIBCXX_TSAN_MUTEX_PRE_LOCK(X)
+#define _GLIBCXX_TSAN_MUTEX_POST_LOCK(X)
+#define _GLIBCXX_TSAN_MUTEX_PRE_UNLOCK(X)
+#define _GLIBCXX_TSAN_MUTEX_POST_UNLOCK(X)
+#define _GLIBCXX_TSAN_MUTEX_PRE_SIGNAL(X)
+#define _GLIBCXX_TSAN_MUTEX_POST_SIGNAL(X)
+#endif
+
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
@@ -377,6 +401,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
~_Atomic_count()
{
auto __val = _M_val.load(memory_order_relaxed);
+ _GLIBCXX_TSAN_MUTEX_DESTROY(&_M_val);
__glibcxx_assert(!(__val & _S_lock_bit));
if (auto __pi = reinterpret_cast<pointer>(__val))
{
@@ -406,6 +431,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__current = _M_val.load(memory_order_relaxed);
}
+ _GLIBCXX_TSAN_MUTEX_PRE_LOCK(&_M_val);
+
while (!_M_val.compare_exchange_strong(__current,
__current | _S_lock_bit,
__o,
@@ -416,6 +443,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#endif
__current = __current & ~_S_lock_bit;
}
+ _GLIBCXX_TSAN_MUTEX_POST_LOCK(&_M_val);
return reinterpret_cast<pointer>(__current);
}
@@ -423,7 +451,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
void
unlock(memory_order __o) const noexcept
{
+ _GLIBCXX_TSAN_MUTEX_PRE_UNLOCK(&_M_val);
_M_val.fetch_sub(1, __o);
+ _GLIBCXX_TSAN_MUTEX_POST_UNLOCK(&_M_val);
}
// Swaps the values of *this and __c, and unlocks *this.
@@ -434,7 +464,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
if (__o != memory_order_seq_cst)
__o = memory_order_release;
auto __x = reinterpret_cast<uintptr_t>(__c._M_pi);
+ _GLIBCXX_TSAN_MUTEX_PRE_UNLOCK(&_M_val);
__x = _M_val.exchange(__x, __o);
+ _GLIBCXX_TSAN_MUTEX_POST_UNLOCK(&_M_val);
__c._M_pi = reinterpret_cast<pointer>(__x & ~_S_lock_bit);
}
@@ -443,20 +475,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
void
_M_wait_unlock(memory_order __o) const noexcept
{
+ _GLIBCXX_TSAN_MUTEX_PRE_UNLOCK(&_M_val);
auto __v = _M_val.fetch_sub(1, memory_order_relaxed);
+ _GLIBCXX_TSAN_MUTEX_POST_UNLOCK(&_M_val);
_M_val.wait(__v & ~_S_lock_bit, __o);
}
void
notify_one() noexcept
{
+ _GLIBCXX_TSAN_MUTEX_PRE_SIGNAL(&_M_val);
_M_val.notify_one();
+ _GLIBCXX_TSAN_MUTEX_POST_SIGNAL(&_M_val);
}
void
notify_all() noexcept
{
+ _GLIBCXX_TSAN_MUTEX_PRE_SIGNAL(&_M_val);
_M_val.notify_all();
+ _GLIBCXX_TSAN_MUTEX_POST_SIGNAL(&_M_val);
}
#endif