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Subject[PATCH] atomic{64}_t: Explicitly specify data storage length and alignment
Date
Atomic instructions require data they operate on to be aligned
according to data size. I.e. 32-bit atomic values must be 32-bit
aligned while 64-bit values must be 64-bit aligned.

Otherwise even if CPU may handle not-aligend normal data access,
still atomic instructions fail and typically raise an exception
leaving us dead in the water.

This came-up during lengthly discussion here:
http://lists.infradead.org/pipermail/linux-snps-arc/2018-July/004022.html

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/arm/include/asm/atomic.h | 2 +-
include/asm-generic/atomic64.h | 2 +-
include/linux/types.h | 4 ++--
tools/include/linux/types.h | 2 +-
tools/testing/selftests/futex/include/atomic.h | 2 +-
.../rcutorture/formal/srcu-cbmc/include/linux/types.h | 4 ++--
6 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/arm/include/asm/atomic.h b/arch/arm/include/asm/atomic.h
index 66d0e215a773..2ed6d7cf1407 100644
--- a/arch/arm/include/asm/atomic.h
+++ b/arch/arm/include/asm/atomic.h
@@ -267,7 +267,7 @@ ATOMIC_OPS(xor, ^=, eor)

#ifndef CONFIG_GENERIC_ATOMIC64
typedef struct {
- long long counter;
+ u64 __aligned(8) counter;
} atomic64_t;

#define ATOMIC64_INIT(i) { (i) }
diff --git a/include/asm-generic/atomic64.h b/include/asm-generic/atomic64.h
index 8d28eb010d0d..b94b749b5952 100644
--- a/include/asm-generic/atomic64.h
+++ b/include/asm-generic/atomic64.h
@@ -13,7 +13,7 @@
#define _ASM_GENERIC_ATOMIC64_H

typedef struct {
- long long counter;
+ u64 __aligned(8) counter;
} atomic64_t;

#define ATOMIC64_INIT(i) { (i) }
diff --git a/include/linux/types.h b/include/linux/types.h
index 9834e90aa010..e2f631782621 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -174,12 +174,12 @@ typedef phys_addr_t resource_size_t;
typedef unsigned long irq_hw_number_t;

typedef struct {
- int counter;
+ u32 __aligned(4) counter;
} atomic_t;

#ifdef CONFIG_64BIT
typedef struct {
- long counter;
+ u64 __aligned(8) counter;
} atomic64_t;
#endif

diff --git a/tools/include/linux/types.h b/tools/include/linux/types.h
index 154eb4e3ca7c..c913e26ea4eb 100644
--- a/tools/include/linux/types.h
+++ b/tools/include/linux/types.h
@@ -59,7 +59,7 @@ typedef __u64 __bitwise __le64;
typedef __u64 __bitwise __be64;

typedef struct {
- int counter;
+ u32 __aligned(4) counter;
} atomic_t;

#ifndef __aligned_u64
diff --git a/tools/testing/selftests/futex/include/atomic.h b/tools/testing/selftests/futex/include/atomic.h
index f861da3e31ab..34e14295e492 100644
--- a/tools/testing/selftests/futex/include/atomic.h
+++ b/tools/testing/selftests/futex/include/atomic.h
@@ -23,7 +23,7 @@
#define _ATOMIC_H

typedef struct {
- volatile int val;
+ volatile u32 __aligned(4) val;
} atomic_t;

#define ATOMIC_INITIALIZER { 0 }
diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/include/linux/types.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/include/linux/types.h
index 891ad13e95b2..32ce965187b3 100644
--- a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/include/linux/types.h
+++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/include/linux/types.h
@@ -100,12 +100,12 @@ typedef phys_addr_t resource_size_t;
typedef unsigned long irq_hw_number_t;

typedef struct {
- int counter;
+ u32 __aligned(4) counter;
} atomic_t;

#ifdef CONFIG_64BIT
typedef struct {
- long counter;
+ u64 __aligned(8) counter;
} atomic64_t;
#endif

--
2.17.1
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