3.5-stable patches

added patches:
	arm-7467-1-mutex-use-generic-xchg-based-implementation-for-armv6.patch

diff --git a/queue-3.5/arm-7467-1-mutex-use-generic-xchg-based-implementation-for-armv6.patch b/queue-3.5/arm-7467-1-mutex-use-generic-xchg-based-implementation-for-armv6.patch
new file mode 100644 (file)
index 0000000..8067dd6
--- /dev/null
+++ b/queue-3.5/arm-7467-1-mutex-use-generic-xchg-based-implementation-for-armv6.patch
@@ -0,0 +1,162 @@
+From a76d7bd96d65fa5119adba97e1b58d95f2e78829 Mon Sep 17 00:00:00 2001
+From: Will Deacon <will.deacon@arm.com>
+Date: Fri, 13 Jul 2012 19:15:40 +0100
+Subject: ARM: 7467/1: mutex: use generic xchg-based implementation for ARMv6+
+
+From: Will Deacon <will.deacon@arm.com>
+
+commit a76d7bd96d65fa5119adba97e1b58d95f2e78829 upstream.
+
+The open-coded mutex implementation for ARMv6+ cores suffers from a
+severe lack of barriers, so in the uncontended case we don't actually
+protect any accesses performed during the critical section.
+
+Furthermore, the code is largely a duplication of the ARMv6+ atomic_dec
+code but optimised to remove a branch instruction, as the mutex fastpath
+was previously inlined. Now that this is executed out-of-line, we can
+reuse the atomic access code for the locking (in fact, we use the xchg
+code as this produces shorter critical sections).
+
+This patch uses the generic xchg based implementation for mutexes on
+ARMv6+, which introduces barriers to the lock/unlock operations and also
+has the benefit of removing a fair amount of inline assembly code.
+
+Acked-by: Arnd Bergmann <arnd@arndb.de>
+Acked-by: Nicolas Pitre <nico@linaro.org>
+Reported-by: Shan Kang <kangshan0910@gmail.com>
+Signed-off-by: Will Deacon <will.deacon@arm.com>
+Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ arch/arm/include/asm/mutex.h |  119 +------------------------------------------
+ 1 file changed, 4 insertions(+), 115 deletions(-)
+
+--- a/arch/arm/include/asm/mutex.h
++++ b/arch/arm/include/asm/mutex.h
+@@ -7,121 +7,10 @@
+  */
+ #ifndef _ASM_MUTEX_H
+ #define _ASM_MUTEX_H
+-
+-#if __LINUX_ARM_ARCH__ < 6
+-/* On pre-ARMv6 hardware the swp based implementation is the most efficient. */
+-# include <asm-generic/mutex-xchg.h>
+-#else
+-
+ /*
+- * Attempting to lock a mutex on ARMv6+ can be done with a bastardized
+- * atomic decrement (it is not a reliable atomic decrement but it satisfies
+- * the defined semantics for our purpose, while being smaller and faster
+- * than a real atomic decrement or atomic swap.  The idea is to attempt
+- * decrementing the lock value only once.  If once decremented it isn't zero,
+- * or if its store-back fails due to a dispute on the exclusive store, we
+- * simply bail out immediately through the slow path where the lock will be
+- * reattempted until it succeeds.
++ * On pre-ARMv6 hardware this results in a swp-based implementation,
++ * which is the most efficient. For ARMv6+, we emit a pair of exclusive
++ * accesses instead.
+  */
+-static inline void
+-__mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
+-{
+-      int __ex_flag, __res;
+-
+-      __asm__ (
+-
+-              "ldrex  %0, [%2]        \n\t"
+-              "sub    %0, %0, #1      \n\t"
+-              "strex  %1, %0, [%2]    "
+-
+-              : "=&r" (__res), "=&r" (__ex_flag)
+-              : "r" (&(count)->counter)
+-              : "cc","memory" );
+-
+-      __res |= __ex_flag;
+-      if (unlikely(__res != 0))
+-              fail_fn(count);
+-}
+-
+-static inline int
+-__mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
+-{
+-      int __ex_flag, __res;
+-
+-      __asm__ (
+-
+-              "ldrex  %0, [%2]        \n\t"
+-              "sub    %0, %0, #1      \n\t"
+-              "strex  %1, %0, [%2]    "
+-
+-              : "=&r" (__res), "=&r" (__ex_flag)
+-              : "r" (&(count)->counter)
+-              : "cc","memory" );
+-
+-      __res |= __ex_flag;
+-      if (unlikely(__res != 0))
+-              __res = fail_fn(count);
+-      return __res;
+-}
+-
+-/*
+- * Same trick is used for the unlock fast path. However the original value,
+- * rather than the result, is used to test for success in order to have
+- * better generated assembly.
+- */
+-static inline void
+-__mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
+-{
+-      int __ex_flag, __res, __orig;
+-
+-      __asm__ (
+-
+-              "ldrex  %0, [%3]        \n\t"
+-              "add    %1, %0, #1      \n\t"
+-              "strex  %2, %1, [%3]    "
+-
+-              : "=&r" (__orig), "=&r" (__res), "=&r" (__ex_flag)
+-              : "r" (&(count)->counter)
+-              : "cc","memory" );
+-
+-      __orig |= __ex_flag;
+-      if (unlikely(__orig != 0))
+-              fail_fn(count);
+-}
+-
+-/*
+- * If the unlock was done on a contended lock, or if the unlock simply fails
+- * then the mutex remains locked.
+- */
+-#define __mutex_slowpath_needs_to_unlock()    1
+-
+-/*
+- * For __mutex_fastpath_trylock we use another construct which could be
+- * described as a "single value cmpxchg".
+- *
+- * This provides the needed trylock semantics like cmpxchg would, but it is
+- * lighter and less generic than a true cmpxchg implementation.
+- */
+-static inline int
+-__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
+-{
+-      int __ex_flag, __res, __orig;
+-
+-      __asm__ (
+-
+-              "1: ldrex       %0, [%3]        \n\t"
+-              "subs           %1, %0, #1      \n\t"
+-              "strexeq        %2, %1, [%3]    \n\t"
+-              "movlt          %0, #0          \n\t"
+-              "cmpeq          %2, #0          \n\t"
+-              "bgt            1b              "
+-
+-              : "=&r" (__orig), "=&r" (__res), "=&r" (__ex_flag)
+-              : "r" (&count->counter)
+-              : "cc", "memory" );
+-
+-      return __orig;
+-}
+-
+-#endif
++#include <asm-generic/mutex-xchg.h>
+ #endif

diff --git a/queue-3.5/series b/queue-3.5/series
index 5196bb72a6c3cfa6c72f7f918234b052019d92b7..1988ab180726045e8c8439b93ef3c87c89fbf8e4 100644 (file)
--- a/queue-3.5/series
+++ b/queue-3.5/series
@@ -259,3 +259,4 @@ md-raid10-fix-enough-function-for-detecting-if-array-is-failed.patch
 drm-udl-limit-modes-to-the-sku-pixel-limits.patch
 drm-i915-only-enable-sdvo-hotplug-irq-if-needed.patch
 vmwgfx-corruption-in-vmw_event_fence_action_create.patch
+arm-7467-1-mutex-use-generic-xchg-based-implementation-for-armv6.patch