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 <arnd@arndb.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Acked-by: Vineet Gupta <vgupta@kernel.org>
Acked-by: Max Filippov <jcmvbkbc@gmail.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Link: https://lore.kernel.org/r/20211026100432.1730393-2-arnd@kernel.org

3 files changed, 0 insertions, 63 deletions

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;
@@ -104,17 +99,6 @@ long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
 	}
 
 	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;
 		fallthrough;
@@ -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;