[PATCH 2/2] futex: remove futex_cmpxchg detection
Christian Borntraeger
borntraeger at de.ibm.com
Tue Oct 26 03:43:43 PDT 2021
Am 26.10.21 um 12:03 schrieb Arnd Bergmann:
> From: Arnd Bergmann <arnd at arndb.de>
>
> Now that all architectures have a working futex implementation
> in any configuration, remove the runtime detection code.
>
> Signed-off-by: Arnd Bergmann <arnd at arndb.de>
s390 part
Acked-by: Christian Borntraeger <borntraeger at de.ibm.com>
> ---
> 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(-)
>
> diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
> index 248389278e8f..f9413041686f 100644
> --- a/arch/arc/Kconfig
> +++ b/arch/arc/Kconfig
> @@ -31,7 +31,6 @@ 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 bb5d2c45477b..6448d311635d 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -93,7 +93,6 @@ 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 0efc501f77aa..6c3c2ff5cef8 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -193,7 +193,6 @@ config ARM64
> select HAVE_PERF_USER_STACK_DUMP
> select HAVE_REGS_AND_STACK_ACCESS_API
> 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 823d3d5a9e11..efd7c5feac8b 100644
> --- a/arch/csky/Kconfig
> +++ b/arch/csky/Kconfig
> @@ -53,7 +53,6 @@ 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 77a088d0a7e9..037fea9fac14 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -84,7 +84,6 @@ 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 f615c3f65f5a..1c9ecf619e04 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -164,7 +164,6 @@ 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 6904f4bdbf00..93195d3368c0 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 c0f55ea5a71f..538688598f2f 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1597,14 +1597,6 @@ 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;
>
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