From 3f2bedabb62c6210df63b604dc988d2f7f56f947 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Tue, 26 Oct 2021 12:03:47 +0200 Subject: futex: Ensure futex_atomic_cmpxchg_inatomic() is present The boot-time detection of futex_atomic_cmpxchg_inatomic() has a bug on some 32-bit arm builds, and Thomas Gleixner suggested that setting CONFIG_HAVE_FUTEX_CMPXCHG would avoid the problem, as it is always present anyway. Looking into which other architectures could do the same showed that almost all architectures have it, the exceptions being: - some old 32-bit MIPS uniprocessor cores without ll/sc - one xtensa variant with no SMP - 32-bit SPARC when built for SMP Fix MIPS And Xtensa by rearranging the generic code to let it be used as a fallback. For SPARC, the SMP definition just ends up turning off futex anyway, so this can be done at Kconfig time instead. Note that sparc32 glibc requires the CASA instruction for its mutexes anyway, which is only available when running on SPARCv9 or LEON CPUs, but needs to be implemented in the sparc32 kernel for those. Signed-off-by: Arnd Bergmann Signed-off-by: Thomas Gleixner Acked-by: Max Filippov Acked-by: Geert Uytterhoeven Acked-by: Rich Felker Link: https://lore.kernel.org/r/20211026100432.1730393-1-arnd@kernel.org --- init/Kconfig | 1 + 1 file changed, 1 insertion(+) (limited to 'init/Kconfig') diff --git a/init/Kconfig b/init/Kconfig index 036b750e8d8a..3f5aa5063f55 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1579,6 +1579,7 @@ config BASE_FULL config FUTEX bool "Enable futex support" if EXPERT + depends on !(SPARC32 && SMP) default y imply RT_MUTEXES help -- cgit v1.2.3 From 3297481d688a5cc2973ea58bd78e66b8639748b1 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Tue, 26 Oct 2021 12:03:48 +0200 Subject: futex: Remove futex_cmpxchg detection Now that all architectures have a working futex implementation in any configuration, remove the runtime detection code. Signed-off-by: Arnd Bergmann Signed-off-by: Thomas Gleixner Reviewed-by: Russell King (Oracle) Acked-by: Vineet Gupta Acked-by: Max Filippov Acked-by: Christian Borntraeger Link: https://lore.kernel.org/r/20211026100432.1730393-2-arnd@kernel.org --- arch/arc/Kconfig | 1 - arch/arm/Kconfig | 1 - arch/arm64/Kconfig | 1 - arch/csky/Kconfig | 1 - arch/m68k/Kconfig | 1 - arch/riscv/Kconfig | 1 - arch/s390/Kconfig | 1 - arch/sh/Kconfig | 1 - arch/um/Kconfig | 1 - arch/um/kernel/skas/uaccess.c | 1 - arch/xtensa/Kconfig | 1 - init/Kconfig | 8 -------- kernel/futex/core.c | 35 ----------------------------------- kernel/futex/futex.h | 6 ------ kernel/futex/syscalls.c | 22 ---------------------- 15 files changed, 82 deletions(-) (limited to 'init/Kconfig') diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig index b4ae6058902a..f74d9860a442 100644 --- a/arch/arc/Kconfig +++ b/arch/arc/Kconfig @@ -32,7 +32,6 @@ config ARC select HAVE_ARCH_TRANSPARENT_HUGEPAGE if ARC_MMU_V4 select HAVE_DEBUG_STACKOVERFLOW select HAVE_DEBUG_KMEMLEAK - select HAVE_FUTEX_CMPXCHG if FUTEX select HAVE_IOREMAP_PROT select HAVE_KERNEL_GZIP select HAVE_KERNEL_LZMA diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index f0f9e8bec83a..2948487346dc 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -92,7 +92,6 @@ config ARM select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL select HAVE_FUNCTION_GRAPH_TRACER if !THUMB2_KERNEL && !CC_IS_CLANG select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !(THUMB2_KERNEL && CC_IS_CLANG) - select HAVE_FUTEX_CMPXCHG if FUTEX select HAVE_GCC_PLUGINS select HAVE_HW_BREAKPOINT if PERF_EVENTS && (CPU_V6 || CPU_V6K || CPU_V7) select HAVE_IRQ_TIME_ACCOUNTING diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index c4207cf9bb17..5e2dfef78956 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -194,7 +194,6 @@ config ARM64 select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_POSIX_CPU_TIMERS_TASK_WORK select HAVE_FUNCTION_ARG_ACCESS_API - select HAVE_FUTEX_CMPXCHG if FUTEX select MMU_GATHER_RCU_TABLE_FREE select HAVE_RSEQ select HAVE_STACKPROTECTOR diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig index aed2b3e734ee..132f43f12dd8 100644 --- a/arch/csky/Kconfig +++ b/arch/csky/Kconfig @@ -52,7 +52,6 @@ config CSKY select HAVE_FUNCTION_TRACER select HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_ERROR_INJECTION - select HAVE_FUTEX_CMPXCHG if FUTEX && SMP select HAVE_FTRACE_MCOUNT_RECORD select HAVE_KERNEL_GZIP select HAVE_KERNEL_LZO diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig index 0b50da08a9c5..15a793c5b2dc 100644 --- a/arch/m68k/Kconfig +++ b/arch/m68k/Kconfig @@ -20,7 +20,6 @@ config M68K select HAVE_ASM_MODVERSIONS select HAVE_DEBUG_BUGVERBOSE select HAVE_EFFICIENT_UNALIGNED_ACCESS if !CPU_HAS_NO_UNALIGNED - select HAVE_FUTEX_CMPXCHG if MMU && FUTEX select HAVE_MOD_ARCH_SPECIFIC select HAVE_UID16 select MMU_GATHER_NO_RANGE if MMU diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 821252b65f89..09abf62ae0ad 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -83,7 +83,6 @@ config RISCV select HAVE_DMA_CONTIGUOUS if MMU select HAVE_EBPF_JIT if MMU select HAVE_FUNCTION_ERROR_INJECTION - select HAVE_FUTEX_CMPXCHG if FUTEX select HAVE_GCC_PLUGINS select HAVE_GENERIC_VDSO if MMU && 64BIT select HAVE_IRQ_TIME_ACCOUNTING diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 8857ec3b97eb..f614562d74f0 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -165,7 +165,6 @@ config S390 select HAVE_FUNCTION_ERROR_INJECTION select HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACER - select HAVE_FUTEX_CMPXCHG if FUTEX select HAVE_GCC_PLUGINS select HAVE_GENERIC_VDSO select HAVE_IOREMAP_PROT if PCI diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig index 70afb30e0b32..2474a04ceac4 100644 --- a/arch/sh/Kconfig +++ b/arch/sh/Kconfig @@ -34,7 +34,6 @@ config SUPERH select HAVE_FAST_GUP if MMU select HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACER - select HAVE_FUTEX_CMPXCHG if FUTEX select HAVE_FTRACE_MCOUNT_RECORD select HAVE_HW_BREAKPOINT select HAVE_IOREMAP_PROT if MMU && !X2TLB diff --git a/arch/um/Kconfig b/arch/um/Kconfig index c18b45f75d41..c906250d4970 100644 --- a/arch/um/Kconfig +++ b/arch/um/Kconfig @@ -14,7 +14,6 @@ config UML select HAVE_ARCH_SECCOMP_FILTER select HAVE_ASM_MODVERSIONS select HAVE_UID16 - select HAVE_FUTEX_CMPXCHG if FUTEX select HAVE_DEBUG_KMEMLEAK select HAVE_DEBUG_BUGVERBOSE select NO_DMA if !UML_DMA_EMULATION diff --git a/arch/um/kernel/skas/uaccess.c b/arch/um/kernel/skas/uaccess.c index a509be911026..9e37a7c05990 100644 --- a/arch/um/kernel/skas/uaccess.c +++ b/arch/um/kernel/skas/uaccess.c @@ -348,7 +348,6 @@ EXPORT_SYMBOL(arch_futex_atomic_op_inuser); * 0 - On success * -EFAULT - User access resulted in a page fault * -EAGAIN - Atomic operation was unable to complete due to contention - * -ENOSYS - Function not implemented (only if !HAVE_FUTEX_CMPXCHG) */ int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig index 0e56bad058fa..8ac599aa6d99 100644 --- a/arch/xtensa/Kconfig +++ b/arch/xtensa/Kconfig @@ -31,7 +31,6 @@ config XTENSA select HAVE_DMA_CONTIGUOUS select HAVE_EXIT_THREAD select HAVE_FUNCTION_TRACER - select HAVE_FUTEX_CMPXCHG if !MMU && FUTEX select HAVE_HW_BREAKPOINT if PERF_EVENTS select HAVE_IRQ_TIME_ACCOUNTING select HAVE_PCI diff --git a/init/Kconfig b/init/Kconfig index 3f5aa5063f55..76d89db5657b 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1592,14 +1592,6 @@ config FUTEX_PI depends on FUTEX && RT_MUTEXES default y -config HAVE_FUTEX_CMPXCHG - bool - depends on FUTEX - help - Architectures should select this if futex_atomic_cmpxchg_inatomic() - is implemented and always working. This removes a couple of runtime - checks. - config EPOLL bool "Enable eventpoll support" if EXPERT default y diff --git a/kernel/futex/core.c b/kernel/futex/core.c index 25d8a88b32e5..926c2bb752bc 100644 --- a/kernel/futex/core.c +++ b/kernel/futex/core.c @@ -41,11 +41,6 @@ #include "futex.h" #include "../locking/rtmutex_common.h" -#ifndef CONFIG_HAVE_FUTEX_CMPXCHG -int __read_mostly futex_cmpxchg_enabled; -#endif - - /* * The base of the bucket array and its size are always used together * (after initialization only in futex_hash()), so ensure that they @@ -776,9 +771,6 @@ static void exit_robust_list(struct task_struct *curr) unsigned long futex_offset; int rc; - if (!futex_cmpxchg_enabled) - return; - /* * Fetch the list head (which was registered earlier, via * sys_set_robust_list()): @@ -874,9 +866,6 @@ static void compat_exit_robust_list(struct task_struct *curr) compat_long_t futex_offset; int rc; - if (!futex_cmpxchg_enabled) - return; - /* * Fetch the list head (which was registered earlier, via * sys_set_robust_list()): @@ -950,8 +939,6 @@ static void exit_pi_state_list(struct task_struct *curr) struct futex_hash_bucket *hb; union futex_key key = FUTEX_KEY_INIT; - if (!futex_cmpxchg_enabled) - return; /* * We are a ZOMBIE and nobody can enqueue itself on * pi_state_list anymore, but we have to be careful @@ -1125,26 +1112,6 @@ void futex_exit_release(struct task_struct *tsk) futex_cleanup_end(tsk, FUTEX_STATE_DEAD); } -static void __init futex_detect_cmpxchg(void) -{ -#ifndef CONFIG_HAVE_FUTEX_CMPXCHG - u32 curval; - - /* - * This will fail and we want it. Some arch implementations do - * runtime detection of the futex_atomic_cmpxchg_inatomic() - * functionality. We want to know that before we call in any - * of the complex code paths. Also we want to prevent - * registration of robust lists in that case. NULL is - * guaranteed to fault and we get -EFAULT on functional - * implementation, the non-functional ones will return - * -ENOSYS. - */ - if (futex_cmpxchg_value_locked(&curval, NULL, 0, 0) == -EFAULT) - futex_cmpxchg_enabled = 1; -#endif -} - static int __init futex_init(void) { unsigned int futex_shift; @@ -1163,8 +1130,6 @@ static int __init futex_init(void) futex_hashsize, futex_hashsize); futex_hashsize = 1UL << futex_shift; - futex_detect_cmpxchg(); - for (i = 0; i < futex_hashsize; i++) { atomic_set(&futex_queues[i].waiters, 0); plist_head_init(&futex_queues[i].chain); diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h index 040ae4277cb0..c264cbeab71c 100644 --- a/kernel/futex/futex.h +++ b/kernel/futex/futex.h @@ -27,12 +27,6 @@ #define FLAGS_CLOCKRT 0x02 #define FLAGS_HAS_TIMEOUT 0x04 -#ifdef CONFIG_HAVE_FUTEX_CMPXCHG -#define futex_cmpxchg_enabled 1 -#else -extern int __read_mostly futex_cmpxchg_enabled; -#endif - #ifdef CONFIG_FAIL_FUTEX extern bool should_fail_futex(bool fshared); #else diff --git a/kernel/futex/syscalls.c b/kernel/futex/syscalls.c index 6f91a07a6a83..086a22d1adb7 100644 --- a/kernel/futex/syscalls.c +++ b/kernel/futex/syscalls.c @@ -29,8 +29,6 @@ SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, size_t, len) { - if (!futex_cmpxchg_enabled) - return -ENOSYS; /* * The kernel knows only one size for now: */ @@ -56,9 +54,6 @@ SYSCALL_DEFINE3(get_robust_list, int, pid, unsigned long ret; struct task_struct *p; - if (!futex_cmpxchg_enabled) - return -ENOSYS; - rcu_read_lock(); ret = -ESRCH; @@ -103,17 +98,6 @@ long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, return -ENOSYS; } - switch (cmd) { - case FUTEX_LOCK_PI: - case FUTEX_LOCK_PI2: - case FUTEX_UNLOCK_PI: - case FUTEX_TRYLOCK_PI: - case FUTEX_WAIT_REQUEUE_PI: - case FUTEX_CMP_REQUEUE_PI: - if (!futex_cmpxchg_enabled) - return -ENOSYS; - } - switch (cmd) { case FUTEX_WAIT: val3 = FUTEX_BITSET_MATCH_ANY; @@ -323,9 +307,6 @@ COMPAT_SYSCALL_DEFINE2(set_robust_list, struct compat_robust_list_head __user *, head, compat_size_t, len) { - if (!futex_cmpxchg_enabled) - return -ENOSYS; - if (unlikely(len != sizeof(*head))) return -EINVAL; @@ -342,9 +323,6 @@ COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid, unsigned long ret; struct task_struct *p; - if (!futex_cmpxchg_enabled) - return -ENOSYS; - rcu_read_lock(); ret = -ESRCH; -- cgit v1.2.3