Messages in this thread | | | Subject | Re: [PATCH 2/2] futex: remove futex_cmpxchg detection | From | Christian Borntraeger <> | Date | Tue, 26 Oct 2021 12:43:43 +0200 |
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Am 26.10.21 um 12:03 schrieb Arnd Bergmann: > From: Arnd Bergmann <arnd@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@arndb.de>
s390 part Acked-by: Christian Borntraeger <borntraeger@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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