futex: Remove redundant pagefault_disable in futex_atomic_cmpxchg_inatomic()
Michel Lespinasse [Fri, 11 Mar 2011 02:47:31 +0000 (18:47 -0800)]
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>
Cc: Darren Hart <darren@dvhart.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <20110311024731.GB26122@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/arm/include/asm/futex.h

index b33fe70..7133a86 100644 (file)
@@ -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;
 }