[PATCH] atomic{64}_t: Explicitly specify data storage length and alignment

* [PATCH] atomic{64}_t: Explicitly specify data storage length and alignment
@ 2018-07-09 12:47 Alexey Brodkin
  2018-07-09 12:55 ` Geert Uytterhoeven
                   ` (6 more replies)
  0 siblings, 7 replies; 11+ messages in thread
From: Alexey Brodkin @ 2018-07-09 12:47 UTC (permalink / raw)
  To: linux-kernel
  Cc: linux-snps-arc, linux-arch, Alexey Brodkin, Will Deacon,
	Peter Zijlstra, Boqun Feng, Russell King, Arnd Bergmann,
	Thomas Gleixner, Ingo Molnar, Darren Hart, Shuah Khan,
	Paul E. McKenney, Josh Triplett, Steven Rostedt,
	Mathieu Desnoyers, Lai Jiangshan, David Laight,
	Geert Uytterhoeven, Greg Kroah-Hartman

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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