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Date: Fri, 25 Jan 2019 10:46:40 -0800
From: Max Filippov <jcmvbkbc@...il.com>
To: LKML <linux-kernel@...r.kernel.org>
Cc: linux-arch@...r.kernel.org, Max Filippov <jcmvbkbc@...il.com>,
Andy Lutomirski <luto@...nel.org>,
Arnd Bergmann <arnd@...db.de>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Paul Burton <paul.burton@...s.com>,
Ralf Baechle <ralf@...ux-mips.org>,
Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v2] treewide: get rid of HAVE_FUTEX_CMPXCHG
CONFIG_HAVE_FUTEX_CMPXCHG is currently used to determine if
atomic_inatomic is always working or must be probed. For most
architectures it is either selected, or it is known that they always
have futex_atomic_cmpxchg_inatomic working.
Drop HAVE_FUTEX_CMPXCHG from the Kconfig and let architectures that may
not have it working define macro arch_have_futex_cmpxchg that probes
whether futex_atomic_cmpxchg_inatomic is working, otherwise assume that
it is working.
Implement arch_have_futex_cmpxchg for MIPS, Xtensa and for the users of
asm-generic/futex.h.
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Paul Burton <paul.burton@...s.com>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Suggested-by: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Max Filippov <jcmvbkbc@...il.com>
---
Changes v1->v2:
- fix #ifdef/#ifndef logic in kernel/futex.c
arch/arc/Kconfig | 1 -
arch/m68k/Kconfig | 1 -
arch/mips/include/asm/futex.h | 2 ++
arch/riscv/Kconfig | 1 -
arch/s390/Kconfig | 1 -
arch/sh/Kconfig | 1 -
arch/um/Kconfig | 1 -
arch/xtensa/Kconfig | 1 -
arch/xtensa/include/asm/futex.h | 4 ++++
include/asm-generic/futex.h | 2 ++
init/Kconfig | 8 --------
kernel/futex.c | 30 ++++++++----------------------
12 files changed, 16 insertions(+), 37 deletions(-)
diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 376366a7db81..01932be9f7e3 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -29,7 +29,6 @@ config ARC
select HAVE_ARCH_KGDB
select HAVE_ARCH_TRACEHOOK
select HAVE_DEBUG_STACKOVERFLOW
- select HAVE_FUTEX_CMPXCHG if FUTEX
select HAVE_GENERIC_DMA_COHERENT
select HAVE_IOREMAP_PROT
select HAVE_KERNEL_GZIP
diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index e173ea2ff395..09499af5d22a 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -20,7 +20,6 @@ config M68K
select GENERIC_STRNLEN_USER if MMU
select ARCH_WANT_IPC_PARSE_VERSION
select ARCH_USES_GETTIMEOFFSET if MMU && !COLDFIRE
- select HAVE_FUTEX_CMPXCHG if MMU && FUTEX
select HAVE_MOD_ARCH_SPECIFIC
select MODULES_USE_ELF_REL
select MODULES_USE_ELF_RELA
diff --git a/arch/mips/include/asm/futex.h b/arch/mips/include/asm/futex.h
index c14d798f3888..f61221d080fc 100644
--- a/arch/mips/include/asm/futex.h
+++ b/arch/mips/include/asm/futex.h
@@ -122,6 +122,8 @@ arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
return ret;
}
+#define arch_have_futex_cmpxchg() (cpu_has_llsc)
+
static inline int
futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
u32 oldval, u32 newval)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index feeeaa60697c..074966cdd41d 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -31,7 +31,6 @@ config RISCV
select HAVE_ARCH_AUDITSYSCALL
select HAVE_MEMBLOCK_NODE_MAP
select HAVE_DMA_CONTIGUOUS
- select HAVE_FUTEX_CMPXCHG if FUTEX
select HAVE_GENERIC_DMA_COHERENT
select HAVE_PERF_EVENTS
select HAVE_SYSCALL_TRACEPOINTS
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index ed554b09eb3f..6f3819275d08 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -146,7 +146,6 @@ config S390
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER
- select HAVE_FUTEX_CMPXCHG if FUTEX
select HAVE_GCC_PLUGINS
select HAVE_KERNEL_BZIP2
select HAVE_KERNEL_GZIP
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index a9c36f95744a..a04bc11c8819 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -50,7 +50,6 @@ config SUPERH
select OLD_SIGACTION
select PCI_DOMAINS if PCI
select HAVE_ARCH_AUDITSYSCALL
- select HAVE_FUTEX_CMPXCHG if FUTEX
select HAVE_NMI
select NEED_SG_DMA_LENGTH
diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index ec9711d068b7..38c5ce3b64b1 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -10,7 +10,6 @@ config UML
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_UID16
- select HAVE_FUTEX_CMPXCHG if FUTEX
select HAVE_DEBUG_KMEMLEAK
select HAVE_DEBUG_BUGVERBOSE
select GENERIC_IRQ_SHOW
diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index 7021d1e15909..a4d34de57809 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -25,7 +25,6 @@ config XTENSA
select HAVE_DMA_CONTIGUOUS
select HAVE_EXIT_THREAD
select HAVE_FUNCTION_TRACER
- select HAVE_FUTEX_CMPXCHG if !MMU
select HAVE_HW_BREAKPOINT if PERF_EVENTS
select HAVE_IRQ_TIME_ACCOUNTING
select HAVE_OPROFILE
diff --git a/arch/xtensa/include/asm/futex.h b/arch/xtensa/include/asm/futex.h
index 505d09eff184..ac88d64f94e4 100644
--- a/arch/xtensa/include/asm/futex.h
+++ b/arch/xtensa/include/asm/futex.h
@@ -87,6 +87,10 @@ static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
return ret;
}
+#if !XCHAL_HAVE_S32C1I
+#define arch_have_futex_cmpxchg() (0)
+#endif
+
static inline int
futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
u32 oldval, u32 newval)
diff --git a/include/asm-generic/futex.h b/include/asm-generic/futex.h
index fcb61b4659b3..deefe5b22b9b 100644
--- a/include/asm-generic/futex.h
+++ b/include/asm-generic/futex.h
@@ -136,6 +136,8 @@ arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
return ret;
}
+#define arch_have_futex_cmpxchg() (0)
+
static inline int
futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
u32 oldval, u32 newval)
diff --git a/init/Kconfig b/init/Kconfig
index 513fa544a134..351f4c93f932 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1338,14 +1338,6 @@ 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.c b/kernel/futex.c
index be3bff2315ff..1b3695c4c6cc 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -174,7 +174,11 @@
* double_lock_hb() and double_unlock_hb(), respectively.
*/
-#ifdef CONFIG_HAVE_FUTEX_CMPXCHG
+/*
+ * Architectures should define this macro if futex_atomic_cmpxchg_inatomic()
+ * may not be always working.
+ */
+#ifndef arch_have_futex_cmpxchg
#define futex_cmpxchg_enabled 1
#else
static int __read_mostly futex_cmpxchg_enabled;
@@ -3842,26 +3846,6 @@ COMPAT_SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
}
#endif /* CONFIG_COMPAT_32BIT_TIME */
-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 (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT)
- futex_cmpxchg_enabled = 1;
-#endif
-}
-
static int __init futex_init(void)
{
unsigned int futex_shift;
@@ -3880,7 +3864,9 @@ static int __init futex_init(void)
futex_hashsize, futex_hashsize);
futex_hashsize = 1UL << futex_shift;
- futex_detect_cmpxchg();
+#ifdef arch_have_futex_cmpxchg
+ futex_cmpxchg_enabled = arch_have_futex_cmpxchg();
+#endif
for (i = 0; i < futex_hashsize; i++) {
atomic_set(&futex_queues[i].waiters, 0);
--
2.11.0
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