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[PATCH 1/3] Remove __ASSUME_FUTEX_LOCK_PI
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Wed, 18 May 2016 18:57:16 -0300
- Subject: [PATCH 1/3] Remove __ASSUME_FUTEX_LOCK_PI
- Authentication-results: sourceware.org; auth=none
This patch removes __ASSUME_FUTEX_LOCK_PI usage and assumes that
kernel will correctly return if it supports or not
futex_atomic_cmpxchg_inatomic.
Current PI mutex code already has runtime support by calling
prio_inherit_missing and returns ENOTSUP if the futex operation fails
at initialization (it issues a FUTEX_UNLOCK_PI futex operation).
Also, current minimum supported kernel (v3.2) will return ENOSYS if
futex_atomic_cmpxchg_inatomic is not supported in the system:
kernel/futex.c:
2628 long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
2629 u32 __user *uaddr2, u32 val2, u32 val3)
2630 {
2631 int ret = -ENOSYS, cmd = op & FUTEX_CMD_MASK;
[...]
2667 case FUTEX_UNLOCK_PI:
2668 if (futex_cmpxchg_enabled)
2669 ret = futex_unlock_pi(uaddr, flags);
[...]
2686 return ret;
2687 }
The futex_cmpxchg_enabled is initialized by calling cmpxchg_futex_value_locked,
which calls futex_atomic_cmpxchg_inatomic.
For ARM futex_atomic_cmpxchg_inatomic will be either defined (if both
CONFIG_CPU_USE_DOMAINS and CONFIG_SMP are not defined) or use the
default generic implementation that returns ENOSYS.
For m68k is uses the default generic implementation.
For mips futex_atomic_cmpxchg_inatomic will return ENOSYS if cpu has no
'cpu_has_llsc' support (defined by each chip supporte inside kernel).
For sparc, 32-bit kernel will just use default generic implementation,
while 64-bit kernel has support.
Tested on ARM (v3.8 kernel) and x86_64.
* nptl/pthread_mutex_init.c [__ASSUME_FUTEX_LOCK_PI]
(prio_inherit_missing): Remove define.
* sysdeps/unix/sysv/linux/arm/kernel-features.h
(__ASSUME_FUTEX_LOCK_PI): Likewise.
* sysdeps/unix/sysv/linux/kernel-features.h (__ASSUME_FUTEX_LOCK_PI):
Likewise.
* sysdeps/unix/sysv/linux/m68k/kernel-features.h
(__ASSUME_FUTEX_LOCK_PI): Likewise.
* sysdeps/unix/sysv/linux/mips/kernel-features.h
(__ASSUME_FUTEX_LOCK_PI): Likewise.
* sysdeps/unix/sysv/linux/sparc/kernel-features.h
(__ASSUME_FUTEX_LOCK_PI): Likewise.
---
ChangeLog | 15 +++++++++++++++
nptl/pthread_mutex_init.c | 3 ---
sysdeps/unix/sysv/linux/arm/kernel-features.h | 1 -
sysdeps/unix/sysv/linux/kernel-features.h | 4 ----
sysdeps/unix/sysv/linux/m68k/kernel-features.h | 1 -
sysdeps/unix/sysv/linux/mips/kernel-features.h | 1 -
sysdeps/unix/sysv/linux/sparc/kernel-features.h | 1 -
7 files changed, 15 insertions(+), 11 deletions(-)
diff --git a/nptl/pthread_mutex_init.c b/nptl/pthread_mutex_init.c
index 71ac7bc..6e5acb6 100644
--- a/nptl/pthread_mutex_init.c
+++ b/nptl/pthread_mutex_init.c
@@ -37,7 +37,6 @@ static bool
prio_inherit_missing (void)
{
#ifdef __NR_futex
-# ifndef __ASSUME_FUTEX_LOCK_PI
static int tpi_supported;
if (__glibc_unlikely (tpi_supported == 0))
{
@@ -48,8 +47,6 @@ prio_inherit_missing (void)
tpi_supported = INTERNAL_SYSCALL_ERRNO (ret, err) == ENOSYS ? -1 : 1;
}
return __glibc_unlikely (tpi_supported < 0);
-# endif
- return false;
#endif
return true;
}
diff --git a/sysdeps/unix/sysv/linux/arm/kernel-features.h b/sysdeps/unix/sysv/linux/arm/kernel-features.h
index 0a9ed77..6ca607e 100644
--- a/sysdeps/unix/sysv/linux/arm/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/arm/kernel-features.h
@@ -23,7 +23,6 @@
futex_atomic_cmpxchg_inatomic, depending on kernel
configuration. */
#if __LINUX_KERNEL_VERSION < 0x030E03
-# undef __ASSUME_FUTEX_LOCK_PI
# undef __ASSUME_REQUEUE_PI
# undef __ASSUME_SET_ROBUST_LIST
#endif
diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h
index 5a1b204..43b72b1 100644
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -64,10 +64,6 @@
configurations). */
#define __ASSUME_SET_ROBUST_LIST 1
-/* Support for PI futexes was added in 2.6.18 (but some architectures
- lack futex_atomic_cmpxchg_inatomic in some configurations). */
-#define __ASSUME_FUTEX_LOCK_PI 1
-
/* Support for private futexes was added in 2.6.22. */
#define __ASSUME_PRIVATE_FUTEX 1
diff --git a/sysdeps/unix/sysv/linux/m68k/kernel-features.h b/sysdeps/unix/sysv/linux/m68k/kernel-features.h
index 646bc4b..9e7f0e1 100644
--- a/sysdeps/unix/sysv/linux/m68k/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/m68k/kernel-features.h
@@ -51,7 +51,6 @@
/* No support for PI futexes or robust mutexes before 3.10 for m68k. */
#if __LINUX_KERNEL_VERSION < 0x030a00
-# undef __ASSUME_FUTEX_LOCK_PI
# undef __ASSUME_REQUEUE_PI
# undef __ASSUME_SET_ROBUST_LIST
#endif
diff --git a/sysdeps/unix/sysv/linux/mips/kernel-features.h b/sysdeps/unix/sysv/linux/mips/kernel-features.h
index e831645..09d5ece 100644
--- a/sysdeps/unix/sysv/linux/mips/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/mips/kernel-features.h
@@ -24,7 +24,6 @@
/* The MIPS kernel does not support futex_atomic_cmpxchg_inatomic if
emulating LL/SC. */
#if __mips == 1 || defined _MIPS_ARCH_R5900
-# undef __ASSUME_FUTEX_LOCK_PI
# undef __ASSUME_REQUEUE_PI
# undef __ASSUME_SET_ROBUST_LIST
#endif
diff --git a/sysdeps/unix/sysv/linux/sparc/kernel-features.h b/sysdeps/unix/sysv/linux/sparc/kernel-features.h
index 386f230..69c9c7c 100644
--- a/sysdeps/unix/sysv/linux/sparc/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/sparc/kernel-features.h
@@ -34,7 +34,6 @@
/* 32-bit SPARC kernels do not support
futex_atomic_cmpxchg_inatomic. */
#if !defined __arch64__ && !defined __sparc_v9__
-# undef __ASSUME_FUTEX_LOCK_PI
# undef __ASSUME_REQUEUE_PI
# undef __ASSUME_SET_ROBUST_LIST
#endif
--
2.7.4