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[PATCH 4.0 23/58] ARC: add smp barriers around atomics per Documentation/atomic_ops.txt

From Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups linux.kernel
Subject [PATCH 4.0 23/58] ARC: add smp barriers around atomics per Documentation/atomic_ops.txt
Date 2015-07-19 21:20 +0200
Message-ID <pO2hZ-3q1-57@gated-at.bofh.it> (permalink)
References <pO2hX-3q1-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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4.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vineet Gupta <vgupta@synopsys.com>

commit 2576c28e3f623ed401db7e6197241865328620ef upstream.

 - arch_spin_lock/unlock were lacking the ACQUIRE/RELEASE barriers
   Since ARCv2 only provides load/load, store/store and all/all, we need
   the full barrier

 - LLOCK/SCOND based atomics, bitops, cmpxchg, which return modified
   values were lacking the explicit smp barriers.

 - Non LLOCK/SCOND varaints don't need the explicit barriers since that
   is implicity provided by the spin locks used to implement the
   critical section (the spin lock barriers in turn are also fixed in
   this commit as explained above

Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arc/include/asm/atomic.h   |   21 +++++++++++++++++++++
 arch/arc/include/asm/bitops.h   |   19 +++++++++++++++++++
 arch/arc/include/asm/cmpxchg.h  |   17 +++++++++++++++++
 arch/arc/include/asm/spinlock.h |   32 ++++++++++++++++++++++++++++++++
 4 files changed, 89 insertions(+)

--- a/arch/arc/include/asm/atomic.h
+++ b/arch/arc/include/asm/atomic.h
@@ -43,6 +43,12 @@ static inline int atomic_##op##_return(i
 {									\
 	unsigned int temp;						\
 									\
+	/*								\
+	 * Explicit full memory barrier needed before/after as		\
+	 * LLOCK/SCOND thmeselves don't provide any such semantics	\
+	 */								\
+	smp_mb();							\
+									\
 	__asm__ __volatile__(						\
 	"1:	llock   %0, [%1]	\n"				\
 	"	" #asm_op " %0, %0, %2	\n"				\
@@ -52,6 +58,8 @@ static inline int atomic_##op##_return(i
 	: "r"(&v->counter), "ir"(i)					\
 	: "cc");							\
 									\
+	smp_mb();							\
+									\
 	return temp;							\
 }
 
@@ -105,6 +113,9 @@ static inline int atomic_##op##_return(i
 	unsigned long flags;						\
 	unsigned long temp;						\
 									\
+	/*								\
+	 * spin lock/unlock provides the needed smp_mb() before/after	\
+	 */								\
 	atomic_ops_lock(flags);						\
 	temp = v->counter;						\
 	temp c_op i;							\
@@ -142,9 +153,19 @@ ATOMIC_OP(and, &=, and)
 #define __atomic_add_unless(v, a, u)					\
 ({									\
 	int c, old;							\
+									\
+	/*								\
+	 * Explicit full memory barrier needed before/after as		\
+	 * LLOCK/SCOND thmeselves don't provide any such semantics	\
+	 */								\
+	smp_mb();							\
+									\
 	c = atomic_read(v);						\
 	while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c)\
 		c = old;						\
+									\
+	smp_mb();							\
+									\
 	c;								\
 })
 
--- a/arch/arc/include/asm/bitops.h
+++ b/arch/arc/include/asm/bitops.h
@@ -103,6 +103,12 @@ static inline int test_and_set_bit(unsig
 	if (__builtin_constant_p(nr))
 		nr &= 0x1f;
 
+	/*
+	 * Explicit full memory barrier needed before/after as
+	 * LLOCK/SCOND themselves don't provide any such semantics
+	 */
+	smp_mb();
+
 	__asm__ __volatile__(
 	"1:	llock   %0, [%2]	\n"
 	"	bset    %1, %0, %3	\n"
@@ -112,6 +118,8 @@ static inline int test_and_set_bit(unsig
 	: "r"(m), "ir"(nr)
 	: "cc");
 
+	smp_mb();
+
 	return (old & (1 << nr)) != 0;
 }
 
@@ -125,6 +133,8 @@ test_and_clear_bit(unsigned long nr, vol
 	if (__builtin_constant_p(nr))
 		nr &= 0x1f;
 
+	smp_mb();
+
 	__asm__ __volatile__(
 	"1:	llock   %0, [%2]	\n"
 	"	bclr    %1, %0, %3	\n"
@@ -134,6 +144,8 @@ test_and_clear_bit(unsigned long nr, vol
 	: "r"(m), "ir"(nr)
 	: "cc");
 
+	smp_mb();
+
 	return (old & (1 << nr)) != 0;
 }
 
@@ -147,6 +159,8 @@ test_and_change_bit(unsigned long nr, vo
 	if (__builtin_constant_p(nr))
 		nr &= 0x1f;
 
+	smp_mb();
+
 	__asm__ __volatile__(
 	"1:	llock   %0, [%2]	\n"
 	"	bxor    %1, %0, %3	\n"
@@ -156,6 +170,8 @@ test_and_change_bit(unsigned long nr, vo
 	: "r"(m), "ir"(nr)
 	: "cc");
 
+	smp_mb();
+
 	return (old & (1 << nr)) != 0;
 }
 
@@ -235,6 +251,9 @@ static inline int test_and_set_bit(unsig
 	if (__builtin_constant_p(nr))
 		nr &= 0x1f;
 
+	/*
+	 * spin lock/unlock provide the needed smp_mb() before/after
+	 */
 	bitops_lock(flags);
 
 	old = *m;
--- a/arch/arc/include/asm/cmpxchg.h
+++ b/arch/arc/include/asm/cmpxchg.h
@@ -10,6 +10,8 @@
 #define __ASM_ARC_CMPXCHG_H
 
 #include <linux/types.h>
+
+#include <asm/barrier.h>
 #include <asm/smp.h>
 
 #ifdef CONFIG_ARC_HAS_LLSC
@@ -19,6 +21,12 @@ __cmpxchg(volatile void *ptr, unsigned l
 {
 	unsigned long prev;
 
+	/*
+	 * Explicit full memory barrier needed before/after as
+	 * LLOCK/SCOND thmeselves don't provide any such semantics
+	 */
+	smp_mb();
+
 	__asm__ __volatile__(
 	"1:	llock   %0, [%1]	\n"
 	"	brne    %0, %2, 2f	\n"
@@ -30,6 +38,8 @@ __cmpxchg(volatile void *ptr, unsigned l
 	  "r"(new) /* can't be "ir". scond can't take limm for "b" */
 	: "cc");
 
+	smp_mb();
+
 	return prev;
 }
 
@@ -42,6 +52,9 @@ __cmpxchg(volatile void *ptr, unsigned l
 	int prev;
 	volatile unsigned long *p = ptr;
 
+	/*
+	 * spin lock/unlock provide the needed smp_mb() before/after
+	 */
 	atomic_ops_lock(flags);
 	prev = *p;
 	if (prev == expected)
@@ -77,12 +90,16 @@ static inline unsigned long __xchg(unsig
 
 	switch (size) {
 	case 4:
+		smp_mb();
+
 		__asm__ __volatile__(
 		"	ex  %0, [%1]	\n"
 		: "+r"(val)
 		: "r"(ptr)
 		: "memory");
 
+		smp_mb();
+
 		return val;
 	}
 	return __xchg_bad_pointer();
--- a/arch/arc/include/asm/spinlock.h
+++ b/arch/arc/include/asm/spinlock.h
@@ -22,24 +22,46 @@ static inline void arch_spin_lock(arch_s
 {
 	unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__;
 
+	/*
+	 * This smp_mb() is technically superfluous, we only need the one
+	 * after the lock for providing the ACQUIRE semantics.
+	 * However doing the "right" thing was regressing hackbench
+	 * so keeping this, pending further investigation
+	 */
+	smp_mb();
+
 	__asm__ __volatile__(
 	"1:	ex  %0, [%1]		\n"
 	"	breq  %0, %2, 1b	\n"
 	: "+&r" (tmp)
 	: "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__)
 	: "memory");
+
+	/*
+	 * ACQUIRE barrier to ensure load/store after taking the lock
+	 * don't "bleed-up" out of the critical section (leak-in is allowed)
+	 * http://www.spinics.net/lists/kernel/msg2010409.html
+	 *
+	 * ARCv2 only has load-load, store-store and all-all barrier
+	 * thus need the full all-all barrier
+	 */
+	smp_mb();
 }
 
 static inline int arch_spin_trylock(arch_spinlock_t *lock)
 {
 	unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__;
 
+	smp_mb();
+
 	__asm__ __volatile__(
 	"1:	ex  %0, [%1]		\n"
 	: "+r" (tmp)
 	: "r"(&(lock->slock))
 	: "memory");
 
+	smp_mb();
+
 	return (tmp == __ARCH_SPIN_LOCK_UNLOCKED__);
 }
 
@@ -47,12 +69,22 @@ static inline void arch_spin_unlock(arch
 {
 	unsigned int tmp = __ARCH_SPIN_LOCK_UNLOCKED__;
 
+	/*
+	 * RELEASE barrier: given the instructions avail on ARCv2, full barrier
+	 * is the only option
+	 */
+	smp_mb();
+
 	__asm__ __volatile__(
 	"	ex  %0, [%1]		\n"
 	: "+r" (tmp)
 	: "r"(&(lock->slock))
 	: "memory");
 
+	/*
+	 * superfluous, but keeping for now - see pairing version in
+	 * arch_spin_lock above
+	 */
 	smp_mb();
 }
 


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[PATCH 4.0 00/58] 4.0.9-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 36/58] regmap: Fix possible shift overflow in regmap_field_init() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 57/58] of/pci: Fix pci_address_to_pio() conversion of CPU address to I/O port Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 35/58] regmap: Fix regmap_bulk_read in BE mode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 22/58] tools selftests: Fix clean target with make 3.81 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 09/58] sysfs: Create mountpoints with sysfs_create_mount_point Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 20/58] ACPI / PM: Add missing pm_generic_complete() invocation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 33/58] mm, thp: respect MPOL_PREFERRED policy with non-local node Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 24/58] ARC: add compiler barrier to LLSC based cmpxchg Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 44/58] scsi_transport_srp: Fix a race condition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 19/58] ACPI / init: Switch over platform to the ACPI mode later Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 32/58] mm: kmemleak_alloc_percpu() should follow the gfp from per_alloc() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 31/58] mm: kmemleak: allow safe memory scanning during kmemleak disabling Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 18/58] ALSA: hda - Fix the dock headphone output on Fujitsu Lifebook E780 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 23/58] ARC: add smp barriers around atomics per Documentation/atomic_ops.txt Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 07/58] mnt: Refactor the logic for mounting sysfs and proc in a user namespace Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 26/58] mei: txe: reduce suspend/resume time Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 15/58] ALSA: hda - Fix Dock Headphone on Thinkpad X250 seen as a Line Out Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 29/58] arm64: mm: Fix freeing of the wrong memmap entries with !SPARSEMEM_VMEMMAP Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 30/58] arm64: vdso: work-around broken ELF toolchains in Makefile Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 25/58] mei: me: wait for power gating exit confirmation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 27/58] arm64: Do not attempt to use init_mm in reset_context() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 28/58] arm64: entry: fix context tracking for el0_sp_pc Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 21/58] iio: accel: kxcjk-1013: add the "KXCJ9000" ACPI id Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
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  [PATCH 4.0 16/58] ALSA: hda - set proper caps for newer AMD hda audio in KB/KV Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 58/58] Input: pixcir_i2c_ts - fix receive error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:20 +0200
  [PATCH 4.0 02/58] sysctl: Allow creating permanently empty directories that serve as mountpoints. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 39/58] livepatch: add module locking around kallsyms calls Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 55/58] PCI: Add pci_bus_addr_t Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 41/58] spi: orion: Fix maximum baud rates for Armada 370/XP Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 52/58] mtd: fix: avoid race condition when accessing mtd->usecount Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 14/58] ALSA: pcm: Fix pcm_class sysfs output Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 38/58] regulator: core: fix constraints output buffer Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 05/58] sysfs: Add support for permanently empty directories to serve as mount points. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 12/58] ipr: Increase default adapter init stage change timeout Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 37/58] regulator: max77686: fix gpio_enabled shift wrapping bug Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 47/58] IB/srp: Fix connection state tracking Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 56/58] PCI: pciehp: Wait for hotplug command completion where necessary Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 42/58] spi: pl022: Specify num-cs property as required in devicetree binding Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 43/58] scsi_transport_srp: Introduce srp_wait_for_queuecommand() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 48/58] IB/srp: Fix reconnection failure handling Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 45/58] IB/srp: Remove an extraneous scsi_host_put() from an error path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 03/58] proc: Allow creating permanently empty directories that serve as mount points Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 13/58] Disable write buffering on Toshiba ToPIC95 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 46/58] IB/srp: Fix a connection setup race Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 54/58] PCI: Propagate the "ignore hotplug" setting to parent Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
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  [PATCH 4.0 50/58] video: mxsfb: Make sure axi clock is enabled when accessing registers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 06/58] mnt: Update fs_fully_visible to test for permanently empty directories Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 01/58] fs: Add helper functions for permanently empty directories. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 49/58] genirq: devres: Fix testing return value of request_any_context_irq() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 10/58] gpio: crystalcove: set IRQCHIP_SKIP_SET_WAKE for the irqchip Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  [PATCH 4.0 51/58] leds / PM: fix hibernation on arm when gpio-led used with CPU led trigger Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-07-19 21:30 +0200
  Re: [PATCH 4.0 00/58] 4.0.9-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2015-07-20 19:20 +0200

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