From f5c77f78ec03363d5e550c4996deb75ee3f2e32a Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Mon, 16 May 2016 10:35:25 -0300 Subject: 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. --- sysdeps/unix/sysv/linux/kernel-features.h | 4 ---- 1 file changed, 4 deletions(-) (limited to 'sysdeps/unix/sysv/linux/kernel-features.h') diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h index 02c530b9e6..1d3b554f81 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 -- cgit 1.4.1