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authorHeiko Carstens <heiko.carstens@de.ibm.com>2014-03-02 13:09:47 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-04-14 06:42:19 -0700
commitf26c70a452dc0507bf7d3d2c3158ee7808e14f1c (patch)
tree7626bda5305bd7c9013d48ef50d030ade70b4b70 /kernel
parent47c4534a109e45700d1d1c8467c2b5a618212d81 (diff)
futex: Allow architectures to skip futex_atomic_cmpxchg_inatomic() test
commit 03b8c7b623c80af264c4c8d6111e5c6289933666 upstream. If an architecture has futex_atomic_cmpxchg_inatomic() implemented and there is no runtime check necessary, allow to skip the test within futex_init(). This allows to get rid of some code which would always give the same result, and also allows the compiler to optimize a couple of if statements away. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Finn Thain <fthain@telegraphics.com.au> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Link: http://lkml.kernel.org/r/20140302120947.GA3641@osiris Signed-off-by: Thomas Gleixner <tglx@linutronix.de> [geert: Backported to v3.10..v3.13] Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/futex.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index a283b3041072..3bc18bf48d0c 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -67,7 +67,9 @@
#include "rtmutex_common.h"
+#ifndef CONFIG_HAVE_FUTEX_CMPXCHG
int __read_mostly futex_cmpxchg_enabled;
+#endif
#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
@@ -2729,10 +2731,10 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
}
-static int __init futex_init(void)
+static void __init futex_detect_cmpxchg(void)
{
+#ifndef CONFIG_HAVE_FUTEX_CMPXCHG
u32 curval;
- int i;
/*
* This will fail and we want it. Some arch implementations do
@@ -2746,6 +2748,14 @@ static int __init futex_init(void)
*/
if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT)
futex_cmpxchg_enabled = 1;
+#endif
+}
+
+static int __init futex_init(void)
+{
+ int i;
+
+ futex_detect_cmpxchg();
for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
plist_head_init(&futex_queues[i].chain);