[PATCH 1/3] futex: do not pagefault_disable in futex_atomic_cmpxchg_inatomic()

[Michel Lespinasse <walken@google.com>]

kernel/futex.c disables page faults before calling
futex_atomic_cmpxchg_inatomic(), so there is no need to do it again
within that function.
    
Signed-off-by: Michel Lespinasse <walken@google.com>

diff --git a/arch/arm/include/asm/futex.h b/arch/arm/include/asm/futex.h
index b33fe70..7133a86 100644
--- a/arch/arm/include/asm/futex.h
+++ b/arch/arm/include/asm/futex.h
@@ -95,7 +95,8 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
 	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
 		return -EFAULT;
 
-	pagefault_disable();	/* implies preempt_disable() */
+	/* Note that preemption is disabled by futex_atomic_cmpxchg_inatomic
+	 * call sites. */
 
 	__asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n"
 	"1:	" T(ldr) "	%0, [%3]\n"
@@ -115,8 +116,6 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
 	: "r" (oldval), "r" (newval), "r" (uaddr), "Ir" (-EFAULT)
 	: "cc", "memory");
 
-	pagefault_enable();	/* subsumes preempt_enable() */
-
 	return val;
 }
 
-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.