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Remove __ASSUME_FUTEX_LOCK_PI 

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.
This commit is contained in:
Adhemerval Zanella 2016-05-16 10:35:25 -03:00
parent 0677af20bb
commit f5c77f78ec
7 changed files with 15 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
ChangeLog
View File

@ -1,3 +1,18 @@
2016-06-13 Adhemerval Zanella <adhemerval.zanella@linaro.org>
* 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.
2016-06-11 Paul Pluzhnikov <ppluzhnikov@google.com>
[BZ #19670]

3
nptl/pthread_mutex_init.c
View File

@ -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;
}

1
sysdeps/unix/sysv/linux/arm/kernel-features.h
View File

@ -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

4
sysdeps/unix/sysv/linux/kernel-features.h
View File

@ -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

1
sysdeps/unix/sysv/linux/m68k/kernel-features.h
View File

@ -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

1
sysdeps/unix/sysv/linux/mips/kernel-features.h
View File

@ -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

1
sysdeps/unix/sysv/linux/sparc/kernel-features.h
View File

@ -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