aboutsummaryrefslogtreecommitdiff
path: root/sysdeps
diff options
context:
space:
mode:
authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2017-10-19 10:11:57 -0200
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2017-11-07 09:48:41 -0200
commit06be6368da16104be51ebf23f7c68a51f321673f (patch)
treed640b3fadbde34dce828f6648629786a9392b655 /sysdeps
parent72b3c6eecde494a31dffa5604d551f88be859d73 (diff)
downloadglibc-06be6368da16104be51ebf23f7c68a51f321673f.zip
glibc-06be6368da16104be51ebf23f7c68a51f321673f.tar.gz
glibc-06be6368da16104be51ebf23f7c68a51f321673f.tar.bz2
nptl: Define __PTHREAD_MUTEX_{NUSERS_AFTER_KIND,USE_UNION}
This patch adds two new internal defines to set the internal pthread_mutex_t layout required by the supported ABIS: 1. __PTHREAD_MUTEX_NUSERS_AFTER_KIND which control whether to define __nusers fields before or after __kind. The preferred value for is 0 for new ports and it sets __nusers before __kind. 2. __PTHREAD_MUTEX_USE_UNION which control whether internal __spins and __list members will be place inside an union for linuxthreads compatibility. The preferred value is 0 for ports and it sets to not use an union to define both fields. It fixes the wrong offsets value for __kind value on x86_64-linux-gnu-x32. Checked with a make check run-built-tests=no on all afected ABIs. [BZ #22298] * nptl/allocatestack.c (allocate_stack): Check if __PTHREAD_MUTEX_HAVE_PREV is non-zero, instead if __PTHREAD_MUTEX_HAVE_PREV is defined. * nptl/descr.h (pthread): Likewise. * nptl/nptl-init.c (__pthread_initialize_minimal_internal): Likewise. * nptl/pthread_create.c (START_THREAD_DEFN): Likewise. * sysdeps/nptl/fork.c (__libc_fork): Likewise. * sysdeps/nptl/pthread.h (PTHREAD_MUTEX_INITIALIZER): Likewise. * sysdeps/nptl/bits/thread-shared-types.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): New defines. (__pthread_internal_list): Check __PTHREAD_MUTEX_USE_UNION instead of __WORDSIZE for internal layout. (__pthread_mutex_s): Check __PTHREAD_MUTEX_NUSERS_AFTER_KIND instead of __WORDSIZE for internal __nusers layout and __PTHREAD_MUTEX_USE_UNION instead of __WORDSIZE whether to use an union for __spins and __list fields. (__PTHREAD_MUTEX_HAVE_PREV): Define also for __PTHREAD_MUTEX_USE_UNION case. * sysdeps/aarch64/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): New defines. * sysdeps/alpha/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): Likewise. * sysdeps/arm/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): Likewise. * sysdeps/hppa/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): Likewise. * sysdeps/ia64/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): Likewise. * sysdeps/m68k/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): Likewise. * sysdeps/microblaze/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): Likewise. * sysdeps/mips/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): Likewise. * sysdeps/nios2/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): Likewise. * sysdeps/powerpc/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): Likewise. * sysdeps/s390/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): Likewise. * sysdeps/sh/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): Likewise. * sysdeps/sparc/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): Likewise. * sysdeps/tile/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): Likewise. * sysdeps/x86/nptl/bits/pthreadtypes-arch.h (__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): Likewise. Signed-off-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Diffstat (limited to 'sysdeps')
-rw-r--r--sysdeps/aarch64/nptl/bits/pthreadtypes-arch.h2
-rw-r--r--sysdeps/alpha/nptl/bits/pthreadtypes-arch.h2
-rw-r--r--sysdeps/arm/nptl/bits/pthreadtypes-arch.h2
-rw-r--r--sysdeps/hppa/nptl/bits/pthreadtypes-arch.h2
-rw-r--r--sysdeps/ia64/nptl/bits/pthreadtypes-arch.h2
-rw-r--r--sysdeps/m68k/nptl/bits/pthreadtypes-arch.h2
-rw-r--r--sysdeps/microblaze/nptl/bits/pthreadtypes-arch.h2
-rw-r--r--sysdeps/mips/nptl/bits/pthreadtypes-arch.h2
-rw-r--r--sysdeps/nios2/nptl/bits/pthreadtypes-arch.h2
-rw-r--r--sysdeps/nptl/bits/thread-shared-types.h32
-rw-r--r--sysdeps/nptl/fork.c2
-rw-r--r--sysdeps/nptl/pthread.h2
-rw-r--r--sysdeps/powerpc/nptl/bits/pthreadtypes-arch.h2
-rw-r--r--sysdeps/s390/nptl/bits/pthreadtypes-arch.h2
-rw-r--r--sysdeps/sh/nptl/bits/pthreadtypes-arch.h2
-rw-r--r--sysdeps/sparc/nptl/bits/pthreadtypes-arch.h2
-rw-r--r--sysdeps/tile/nptl/bits/pthreadtypes-arch.h2
-rw-r--r--sysdeps/x86/nptl/bits/pthreadtypes-arch.h7
18 files changed, 64 insertions, 7 deletions
diff --git a/sysdeps/aarch64/nptl/bits/pthreadtypes-arch.h b/sysdeps/aarch64/nptl/bits/pthreadtypes-arch.h
index d13a75d..9ab23d0 100644
--- a/sysdeps/aarch64/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/aarch64/nptl/bits/pthreadtypes-arch.h
@@ -45,6 +45,8 @@
#define __PTHREAD_COMPAT_PADDING_MID
#define __PTHREAD_COMPAT_PADDING_END
#define __PTHREAD_MUTEX_LOCK_ELISION 0
+#define __PTHREAD_MUTEX_NUSERS_AFTER_KIND 0
+#define __PTHREAD_MUTEX_USE_UNION 0
#define __LOCK_ALIGNMENT
#define __ONCE_ALIGNMENT
diff --git a/sysdeps/alpha/nptl/bits/pthreadtypes-arch.h b/sysdeps/alpha/nptl/bits/pthreadtypes-arch.h
index b6f6cb1..429df10 100644
--- a/sysdeps/alpha/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/alpha/nptl/bits/pthreadtypes-arch.h
@@ -33,6 +33,8 @@
#define __PTHREAD_COMPAT_PADDING_MID
#define __PTHREAD_COMPAT_PADDING_END
#define __PTHREAD_MUTEX_LOCK_ELISION 0
+#define __PTHREAD_MUTEX_NUSERS_AFTER_KIND 0
+#define __PTHREAD_MUTEX_USE_UNION 0
#define __LOCK_ALIGNMENT
#define __ONCE_ALIGNMENT
diff --git a/sysdeps/arm/nptl/bits/pthreadtypes-arch.h b/sysdeps/arm/nptl/bits/pthreadtypes-arch.h
index 3f9eca4..3911c81 100644
--- a/sysdeps/arm/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/arm/nptl/bits/pthreadtypes-arch.h
@@ -34,6 +34,8 @@
#define __PTHREAD_COMPAT_PADDING_MID
#define __PTHREAD_COMPAT_PADDING_END
#define __PTHREAD_MUTEX_LOCK_ELISION 0
+#define __PTHREAD_MUTEX_NUSERS_AFTER_KIND 1
+#define __PTHREAD_MUTEX_USE_UNION 1
#define __LOCK_ALIGNMENT
#define __ONCE_ALIGNMENT
diff --git a/sysdeps/hppa/nptl/bits/pthreadtypes-arch.h b/sysdeps/hppa/nptl/bits/pthreadtypes-arch.h
index c158562..865a14e 100644
--- a/sysdeps/hppa/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/hppa/nptl/bits/pthreadtypes-arch.h
@@ -48,6 +48,8 @@
pthread_mutex_t is larger than Linuxthreads. */
#define __PTHREAD_COMPAT_PADDING_END int __reserved[2];
#define __PTHREAD_MUTEX_LOCK_ELISION 0
+#define __PTHREAD_MUTEX_NUSERS_AFTER_KIND 1
+#define __PTHREAD_MUTEX_USE_UNION 1
#define __LOCK_ALIGNMENT __attribute__ ((__aligned__(16)))
#define __ONCE_ALIGNMENT
diff --git a/sysdeps/ia64/nptl/bits/pthreadtypes-arch.h b/sysdeps/ia64/nptl/bits/pthreadtypes-arch.h
index 631cb33..2a3bc75 100644
--- a/sysdeps/ia64/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/ia64/nptl/bits/pthreadtypes-arch.h
@@ -33,6 +33,8 @@
#define __PTHREAD_COMPAT_PADDING_MID
#define __PTHREAD_COMPAT_PADDING_END
#define __PTHREAD_MUTEX_LOCK_ELISION 0
+#define __PTHREAD_MUTEX_NUSERS_AFTER_KIND 0
+#define __PTHREAD_MUTEX_USE_UNION 0
#define __LOCK_ALIGNMENT
#define __ONCE_ALIGNMENT
diff --git a/sysdeps/m68k/nptl/bits/pthreadtypes-arch.h b/sysdeps/m68k/nptl/bits/pthreadtypes-arch.h
index 845b9e6..966cc75 100644
--- a/sysdeps/m68k/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/m68k/nptl/bits/pthreadtypes-arch.h
@@ -35,6 +35,8 @@
#define __PTHREAD_COMPAT_PADDING_MID
#define __PTHREAD_COMPAT_PADDING_END
#define __PTHREAD_MUTEX_LOCK_ELISION 0
+#define __PTHREAD_MUTEX_NUSERS_AFTER_KIND 1
+#define __PTHREAD_MUTEX_USE_UNION 1
#define __LOCK_ALIGNMENT __attribute__ ((__aligned__ (4)))
#define __ONCE_ALIGNMENT __attribute__ ((__aligned__ (4)))
diff --git a/sysdeps/microblaze/nptl/bits/pthreadtypes-arch.h b/sysdeps/microblaze/nptl/bits/pthreadtypes-arch.h
index d687e2c..e44f2dc 100644
--- a/sysdeps/microblaze/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/microblaze/nptl/bits/pthreadtypes-arch.h
@@ -35,6 +35,8 @@
#define __PTHREAD_COMPAT_PADDING_MID
#define __PTHREAD_COMPAT_PADDING_END
#define __PTHREAD_MUTEX_LOCK_ELISION 0
+#define __PTHREAD_MUTEX_NUSERS_AFTER_KIND 1
+#define __PTHREAD_MUTEX_USE_UNION 1
#define __LOCK_ALIGNMENT
#define __ONCE_ALIGNMENT
diff --git a/sysdeps/mips/nptl/bits/pthreadtypes-arch.h b/sysdeps/mips/nptl/bits/pthreadtypes-arch.h
index 6aa1bda..f03389a 100644
--- a/sysdeps/mips/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/mips/nptl/bits/pthreadtypes-arch.h
@@ -42,6 +42,8 @@
#define __PTHREAD_COMPAT_PADDING_MID
#define __PTHREAD_COMPAT_PADDING_END
#define __PTHREAD_MUTEX_LOCK_ELISION 0
+#define __PTHREAD_MUTEX_NUSERS_AFTER_KIND (_MIPS_SIM != _ABI64)
+#define __PTHREAD_MUTEX_USE_UNION (_MIPS_SIM != _ABI64)
#define __LOCK_ALIGNMENT
#define __ONCE_ALIGNMENT
diff --git a/sysdeps/nios2/nptl/bits/pthreadtypes-arch.h b/sysdeps/nios2/nptl/bits/pthreadtypes-arch.h
index e2732f9..83f8684 100644
--- a/sysdeps/nios2/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/nios2/nptl/bits/pthreadtypes-arch.h
@@ -35,6 +35,8 @@
#define __PTHREAD_COMPAT_PADDING_MID
#define __PTHREAD_COMPAT_PADDING_END
#define __PTHREAD_MUTEX_LOCK_ELISION 0
+#define __PTHREAD_MUTEX_NUSERS_AFTER_KIND 1
+#define __PTHREAD_MUTEX_USE_UNION 1
#define __LOCK_ALIGNMENT
#define __ONCE_ALIGNMENT
diff --git a/sysdeps/nptl/bits/thread-shared-types.h b/sysdeps/nptl/bits/thread-shared-types.h
index 68b82b6..da4358a 100644
--- a/sysdeps/nptl/bits/thread-shared-types.h
+++ b/sysdeps/nptl/bits/thread-shared-types.h
@@ -42,6 +42,25 @@
the internal structure.
__PTHREAD_MUTEX_LOCK_ELISION - 1 if the architecture supports lock
elision or 0 otherwise.
+ __PTHREAD_MUTEX_NUSERS_AFTER_KIND - control where to put __nusers. The
+ preferred value for new architectures
+ is 0.
+ __PTHREAD_MUTEX_USE_UNION - control whether internal __spins and
+ __list will be place inside a union for
+ linuxthreads compatibility.
+ The preferred value for new architectures
+ is 0.
+
+ For a new port the preferred values for the required defines are:
+
+ #define __PTHREAD_COMPAT_PADDING_MID
+ #define __PTHREAD_COMPAT_PADDING_END
+ #define __PTHREAD_MUTEX_LOCK_ELISION 0
+ #define __PTHREAD_MUTEX_NUSERS_AFTER_KIND 0
+ #define __PTHREAD_MUTEX_USE_UNION 0
+
+ __PTHREAD_MUTEX_LOCK_ELISION can be set to 1 if the hardware plans to
+ eventually support lock elision using transactional memory.
The additional macro defines any constraint for the lock alignment
inside the thread structures:
@@ -59,7 +78,7 @@
/* Common definition of pthread_mutex_t. */
-#if __WORDSIZE == 64
+#if !__PTHREAD_MUTEX_USE_UNION
typedef struct __pthread_internal_list
{
struct __pthread_internal_list *__prev;
@@ -74,7 +93,7 @@ typedef struct __pthread_internal_slist
/* Lock elision support. */
#if __PTHREAD_MUTEX_LOCK_ELISION
-# if __WORDSIZE == 64
+# if !__PTHREAD_MUTEX_USE_UNION
# define __PTHREAD_SPINS_DATA \
short __spins; \
short __elision
@@ -101,24 +120,27 @@ struct __pthread_mutex_s
int __lock __LOCK_ALIGNMENT;
unsigned int __count;
int __owner;
-#if __WORDSIZE == 64
+#if !__PTHREAD_MUTEX_NUSERS_AFTER_KIND
unsigned int __nusers;
#endif
/* KIND must stay at this position in the structure to maintain
binary compatibility with static initializers. */
int __kind;
__PTHREAD_COMPAT_PADDING_MID
-#if __WORDSIZE == 64
+#if __PTHREAD_MUTEX_NUSERS_AFTER_KIND
+ unsigned int __nusers;
+#endif
+#if !__PTHREAD_MUTEX_USE_UNION
__PTHREAD_SPINS_DATA;
__pthread_list_t __list;
# define __PTHREAD_MUTEX_HAVE_PREV 1
#else
- unsigned int __nusers;
__extension__ union
{
__PTHREAD_SPINS_DATA;
__pthread_slist_t __list;
};
+# define __PTHREAD_MUTEX_HAVE_PREV 0
#endif
__PTHREAD_COMPAT_PADDING_END
};
diff --git a/sysdeps/nptl/fork.c b/sysdeps/nptl/fork.c
index 4bb87e2..48676c2 100644
--- a/sysdeps/nptl/fork.c
+++ b/sysdeps/nptl/fork.c
@@ -166,7 +166,7 @@ __libc_fork (void)
inherit the correct value from the parent. We do not need to clear
the pending operation because it must have been zero when fork was
called. */
-# ifdef __PTHREAD_MUTEX_HAVE_PREV
+# if __PTHREAD_MUTEX_HAVE_PREV
self->robust_prev = &self->robust_head;
# endif
self->robust_head.list = &self->robust_head;
diff --git a/sysdeps/nptl/pthread.h b/sysdeps/nptl/pthread.h
index 632ea7b..2b2b386 100644
--- a/sysdeps/nptl/pthread.h
+++ b/sysdeps/nptl/pthread.h
@@ -83,7 +83,7 @@ enum
#endif
-#ifdef __PTHREAD_MUTEX_HAVE_PREV
+#if __PTHREAD_MUTEX_HAVE_PREV
# define PTHREAD_MUTEX_INITIALIZER \
{ { 0, 0, 0, 0, 0, __PTHREAD_SPINS, { 0, 0 } } }
# ifdef __USE_GNU
diff --git a/sysdeps/powerpc/nptl/bits/pthreadtypes-arch.h b/sysdeps/powerpc/nptl/bits/pthreadtypes-arch.h
index f29119b..8158cb5 100644
--- a/sysdeps/powerpc/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/powerpc/nptl/bits/pthreadtypes-arch.h
@@ -42,6 +42,8 @@
#define __PTHREAD_COMPAT_PADDING_MID
#define __PTHREAD_COMPAT_PADDING_END
#define __PTHREAD_MUTEX_LOCK_ELISION 1
+#define __PTHREAD_MUTEX_NUSERS_AFTER_KIND (__WORDSIZE != 64)
+#define __PTHREAD_MUTEX_USE_UNION (__WORDSIZE != 64)
#define __LOCK_ALIGNMENT
#define __ONCE_ALIGNMENT
diff --git a/sysdeps/s390/nptl/bits/pthreadtypes-arch.h b/sysdeps/s390/nptl/bits/pthreadtypes-arch.h
index 3a9ac57..1ae2773 100644
--- a/sysdeps/s390/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/s390/nptl/bits/pthreadtypes-arch.h
@@ -45,6 +45,8 @@
#else
#define __PTHREAD_MUTEX_LOCK_ELISION 0
#endif
+#define __PTHREAD_MUTEX_NUSERS_AFTER_KIND (__WORDSIZE != 64)
+#define __PTHREAD_MUTEX_USE_UNION (__WORDSIZE != 64)
#define __LOCK_ALIGNMENT
#define __ONCE_ALIGNMENT
diff --git a/sysdeps/sh/nptl/bits/pthreadtypes-arch.h b/sysdeps/sh/nptl/bits/pthreadtypes-arch.h
index b2615fe..e707751 100644
--- a/sysdeps/sh/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/sh/nptl/bits/pthreadtypes-arch.h
@@ -34,6 +34,8 @@
#define __PTHREAD_COMPAT_PADDING_MID
#define __PTHREAD_COMPAT_PADDING_END
#define __PTHREAD_MUTEX_LOCK_ELISION 0
+#define __PTHREAD_MUTEX_NUSERS_AFTER_KIND 1
+#define __PTHREAD_MUTEX_USE_UNION 1
#define __LOCK_ALIGNMENT
#define __ONCE_ALIGNMENT
diff --git a/sysdeps/sparc/nptl/bits/pthreadtypes-arch.h b/sysdeps/sparc/nptl/bits/pthreadtypes-arch.h
index 1e188cf..0f96f37 100644
--- a/sysdeps/sparc/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/sparc/nptl/bits/pthreadtypes-arch.h
@@ -43,6 +43,8 @@
#define __PTHREAD_COMPAT_PADDING_MID
#define __PTHREAD_COMPAT_PADDING_END
#define __PTHREAD_MUTEX_LOCK_ELISION 0
+#define __PTHREAD_MUTEX_NUSERS_AFTER_KIND (__WORDSIZE != 64)
+#define __PTHREAD_MUTEX_USE_UNION (__WORDSIZE != 64)
#define __LOCK_ALIGNMENT
#define __ONCE_ALIGNMENT
diff --git a/sysdeps/tile/nptl/bits/pthreadtypes-arch.h b/sysdeps/tile/nptl/bits/pthreadtypes-arch.h
index 145ee42..054474f 100644
--- a/sysdeps/tile/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/tile/nptl/bits/pthreadtypes-arch.h
@@ -43,6 +43,8 @@
#define __PTHREAD_COMPAT_PADDING_MID
#define __PTHREAD_COMPAT_PADDING_END
#define __PTHREAD_MUTEX_LOCK_ELISION 0
+#define __PTHREAD_MUTEX_NUSERS_AFTER_KIND (__WORDSIZE != 64)
+#define __PTHREAD_MUTEX_USE_UNION (__WORDSIZE != 64)
#define __LOCK_ALIGNMENT
#define __ONCE_ALIGNMENT
diff --git a/sysdeps/x86/nptl/bits/pthreadtypes-arch.h b/sysdeps/x86/nptl/bits/pthreadtypes-arch.h
index fd86806..74d5f6d 100644
--- a/sysdeps/x86/nptl/bits/pthreadtypes-arch.h
+++ b/sysdeps/x86/nptl/bits/pthreadtypes-arch.h
@@ -51,6 +51,13 @@
#define __PTHREAD_COMPAT_PADDING_MID
#define __PTHREAD_COMPAT_PADDING_END
#define __PTHREAD_MUTEX_LOCK_ELISION 1
+#ifdef __x86_64__
+# define __PTHREAD_MUTEX_NUSERS_AFTER_KIND 0
+# define __PTHREAD_MUTEX_USE_UNION 0
+#else
+# define __PTHREAD_MUTEX_NUSERS_AFTER_KIND 1
+# define __PTHREAD_MUTEX_USE_UNION 1
+#endif
#define __LOCK_ALIGNMENT
#define __ONCE_ALIGNMENT