Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2da2ca24 · Linus Torvalds <[email protected]> · 2018-06-24 19:36:16 +08:00

Pull locking fixes from Thomas Gleixner:
 "A set of fixes and updates for the locking code:

   - Prevent lockdep from updating irq state within its own code and
     thereby confusing itself.

   - Buid fix for older GCCs which mistreat anonymous unions

   - Add a missing lockdep annotation in down_read_non_onwer() which
     causes up_read_non_owner() to emit a lockdep splat

   - Remove the custom alpha dec_and_lock() implementation which is
     incorrect in terms of ordering and use the generic one.

  The remaining two commits are not strictly fixes. They provide irqsave
  variants of atomic_dec_and_lock() and refcount_dec_and_lock(). These
  are required to merge the relevant updates and cleanups into different
  maintainer trees for 4.19, so routing them into mainline without
  actual users is the sanest approach.

  They should have been in -rc1, but last weekend I took the liberty to
  just avoid computers in order to regain some mental sanity"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/qspinlock: Fix build for anonymous union in older GCC compilers
  locking/lockdep: Do not record IRQ state within lockdep code
  locking/rwsem: Fix up_read_non_owner() warning with DEBUG_RWSEMS
  locking/refcounts: Implement refcount_dec_and_lock_irqsave()
  atomic: Add irqsave variant of atomic_dec_and_lock()
  alpha: Remove custom dec_and_lock() implementation

Commit: 2da2ca24a38f0200111e3b8823c08d02cb59d362
Parents: a43de489 · 6cc65be4

Merge commit. Changes below are compared with the first parent: a43de489.

Changes

11 files changed · +61 −64

File	Status	Add	Del	Content
arch/alpha/Kconfig	modified	+0	−5	View file
arch/alpha/lib/Makefile	modified	+0	−2	View file
arch/alpha/lib/dec_and_lock.c	deleted	+0	−44	View before deletion
include/asm-generic/qspinlock_types.h	modified	+1	−1	View file
include/linux/refcount.h	modified	+3	−1	View file
include/linux/spinlock.h	modified	+5	−0	View file
kernel/locking/lockdep.c	modified	+6	−6	View file
kernel/locking/rwsem.c	modified	+1	−0	View file
lib/Makefile	modified	+1	−5	View file
lib/dec_and_lock.c	modified	+16	−0	View file
lib/refcount.c	modified	+28	−0	View file

arch/alpha/Kconfig

View file

diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index 0c4805a..04a4a13 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -555,11 +555,6 @@ config SMP
 
 	  If you don't know what to do here, say N.
 
-config HAVE_DEC_LOCK
-	bool
-	depends on SMP
-	default y
-
 config NR_CPUS
 	int "Maximum number of CPUs (2-32)"
 	range 2 32

arch/alpha/lib/Makefile

View file

diff --git a/arch/alpha/lib/Makefile b/arch/alpha/lib/Makefile
index 04f9729..854d5e7 100644
--- a/arch/alpha/lib/Makefile
+++ b/arch/alpha/lib/Makefile
@@ -35,8 +35,6 @@ lib-y =	__divqu.o __remqu.o __divlu.o __remlu.o \
 	callback_srm.o srm_puts.o srm_printk.o \
 	fls.o
 
-lib-$(CONFIG_SMP) += dec_and_lock.o
-
 # The division routines are built from single source, with different defines.
 AFLAGS___divqu.o = -DDIV
 AFLAGS___remqu.o =       -DREM

arch/alpha/lib/dec_and_lock.c

View before deletion

diff --git a/arch/alpha/lib/dec_and_lock.c b/arch/alpha/lib/dec_and_lock.c
deleted file mode 100644
index a117707..0000000
--- a/arch/alpha/lib/dec_and_lock.c
+++ /dev/null
@@ -1,44 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * arch/alpha/lib/dec_and_lock.c
- *
- * ll/sc version of atomic_dec_and_lock()
- * 
- */
-
-#include <linux/spinlock.h>
-#include <linux/atomic.h>
-#include <linux/export.h>
-
-  asm (".text					\n\
-	.global _atomic_dec_and_lock		\n\
-	.ent _atomic_dec_and_lock		\n\
-	.align	4				\n\
-_atomic_dec_and_lock:				\n\
-	.prologue 0				\n\
-1:	ldl_l	$1, 0($16)			\n\
-	subl	$1, 1, $1			\n\
-	beq	$1, 2f				\n\
-	stl_c	$1, 0($16)			\n\
-	beq	$1, 4f				\n\
-	mb					\n\
-	clr	$0				\n\
-	ret					\n\
-2:	br	$29, 3f				\n\
-3:	ldgp	$29, 0($29)			\n\
-	br	$atomic_dec_and_lock_1..ng	\n\
-	.subsection 2				\n\
-4:	br	1b				\n\
-	.previous				\n\
-	.end _atomic_dec_and_lock");
-
-static int __used atomic_dec_and_lock_1(atomic_t *atomic, spinlock_t *lock)
-{
-	/* Slow path */
-	spin_lock(lock);
-	if (atomic_dec_and_test(atomic))
-		return 1;
-	spin_unlock(lock);
-	return 0;
-}
-EXPORT_SYMBOL(_atomic_dec_and_lock);

include/asm-generic/qspinlock_types.h

View file

diff --git a/include/asm-generic/qspinlock_types.h b/include/asm-generic/qspinlock_types.h
index 0763f06..d10f1e7 100644
--- a/include/asm-generic/qspinlock_types.h
+++ b/include/asm-generic/qspinlock_types.h
@@ -63,7 +63,7 @@ typedef struct qspinlock {
 /*
  * Initializier
  */
-#define	__ARCH_SPIN_LOCK_UNLOCKED	{ .val = ATOMIC_INIT(0) }
+#define	__ARCH_SPIN_LOCK_UNLOCKED	{ { .val = ATOMIC_INIT(0) } }
 
 /*
  * Bitfields in the atomic value:

include/linux/refcount.h

View file

diff --git a/include/linux/refcount.h b/include/linux/refcount.h
index 4193c41..a685da2 100644
--- a/include/linux/refcount.h
+++ b/include/linux/refcount.h
@@ -98,5 +98,7 @@ extern __must_check bool refcount_dec_if_one(refcount_t *r);
 extern __must_check bool refcount_dec_not_one(refcount_t *r);
 extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock);
 extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock);
-
+extern __must_check bool refcount_dec_and_lock_irqsave(refcount_t *r,
+						       spinlock_t *lock,
+						       unsigned long *flags);
 #endif /* _LINUX_REFCOUNT_H */

include/linux/spinlock.h

View file

diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index 1e8a464..fd57888 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -427,6 +427,11 @@ extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
 #define atomic_dec_and_lock(atomic, lock) \
 		__cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
 
+extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
+					unsigned long *flags);
+#define atomic_dec_and_lock_irqsave(atomic, lock, flags) \
+		__cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags)))
+
 int alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
 			   size_t max_size, unsigned int cpu_mult,
 			   gfp_t gfp);

kernel/locking/lockdep.c

View file

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index edcac5d..5fa4d31 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1265,11 +1265,11 @@ unsigned long lockdep_count_forward_deps(struct lock_class *class)
 	this.parent = NULL;
 	this.class = class;
 
-	local_irq_save(flags);
+	raw_local_irq_save(flags);
 	arch_spin_lock(&lockdep_lock);
 	ret = __lockdep_count_forward_deps(&this);
 	arch_spin_unlock(&lockdep_lock);
-	local_irq_restore(flags);
+	raw_local_irq_restore(flags);
 
 	return ret;
 }
@@ -1292,11 +1292,11 @@ unsigned long lockdep_count_backward_deps(struct lock_class *class)
 	this.parent = NULL;
 	this.class = class;
 
-	local_irq_save(flags);
+	raw_local_irq_save(flags);
 	arch_spin_lock(&lockdep_lock);
 	ret = __lockdep_count_backward_deps(&this);
 	arch_spin_unlock(&lockdep_lock);
-	local_irq_restore(flags);
+	raw_local_irq_restore(flags);
 
 	return ret;
 }
@@ -4411,7 +4411,7 @@ void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
 	if (unlikely(!debug_locks))
 		return;
 
-	local_irq_save(flags);
+	raw_local_irq_save(flags);
 	for (i = 0; i < curr->lockdep_depth; i++) {
 		hlock = curr->held_locks + i;
 
@@ -4422,7 +4422,7 @@ void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
 		print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
 		break;
 	}
-	local_irq_restore(flags);
+	raw_local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
 

kernel/locking/rwsem.c

View file

diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index bc1e507..776308d 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -181,6 +181,7 @@ void down_read_non_owner(struct rw_semaphore *sem)
 	might_sleep();
 
 	__down_read(sem);
+	rwsem_set_reader_owned(sem);
 }
 
 EXPORT_SYMBOL(down_read_non_owner);

lib/Makefile

View file

diff --git a/lib/Makefile b/lib/Makefile
index 8153fda..90dc552 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -23,7 +23,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 sha1.o chacha20.o irq_regs.o argv_split.o \
 	 flex_proportions.o ratelimit.o show_mem.o \
 	 is_single_threaded.o plist.o decompress.o kobject_uevent.o \
-	 earlycpio.o seq_buf.o siphash.o \
+	 earlycpio.o seq_buf.o siphash.o dec_and_lock.o \
 	 nmi_backtrace.o nodemask.o win_minmax.o
 
 lib-$(CONFIG_PRINTK) += dump_stack.o
@@ -95,10 +95,6 @@ obj-$(CONFIG_DEBUG_PREEMPT) += smp_processor_id.o
 obj-$(CONFIG_DEBUG_LIST) += list_debug.o
 obj-$(CONFIG_DEBUG_OBJECTS) += debugobjects.o
 
-ifneq ($(CONFIG_HAVE_DEC_LOCK),y)
-  lib-y += dec_and_lock.o
-endif
-
 obj-$(CONFIG_BITREVERSE) += bitrev.o
 obj-$(CONFIG_RATIONAL)	+= rational.o
 obj-$(CONFIG_CRC_CCITT)	+= crc-ccitt.o

lib/dec_and_lock.c

View file

diff --git a/lib/dec_and_lock.c b/lib/dec_and_lock.c
index 347fa7a..9555b68 100644
--- a/lib/dec_and_lock.c
+++ b/lib/dec_and_lock.c
@@ -33,3 +33,19 @@ int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
 }
 
 EXPORT_SYMBOL(_atomic_dec_and_lock);
+
+int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
+				 unsigned long *flags)
+{
+	/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
+	if (atomic_add_unless(atomic, -1, 1))
+		return 0;
+
+	/* Otherwise do it the slow way */
+	spin_lock_irqsave(lock, *flags);
+	if (atomic_dec_and_test(atomic))
+		return 1;
+	spin_unlock_irqrestore(lock, *flags);
+	return 0;
+}
+EXPORT_SYMBOL(_atomic_dec_and_lock_irqsave);

lib/refcount.c

View file

diff --git a/lib/refcount.c b/lib/refcount.c
index 0eb4835..d3b81ce 100644
--- a/lib/refcount.c
+++ b/lib/refcount.c
@@ -350,3 +350,31 @@ bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
 }
 EXPORT_SYMBOL(refcount_dec_and_lock);
 
+/**
+ * refcount_dec_and_lock_irqsave - return holding spinlock with disabled
+ *                                 interrupts if able to decrement refcount to 0
+ * @r: the refcount
+ * @lock: the spinlock to be locked
+ * @flags: saved IRQ-flags if the is acquired
+ *
+ * Same as refcount_dec_and_lock() above except that the spinlock is acquired
+ * with disabled interupts.
+ *
+ * Return: true and hold spinlock if able to decrement refcount to 0, false
+ *         otherwise
+ */
+bool refcount_dec_and_lock_irqsave(refcount_t *r, spinlock_t *lock,
+				   unsigned long *flags)
+{
+	if (refcount_dec_not_one(r))
+		return false;
+
+	spin_lock_irqsave(lock, *flags);
+	if (!refcount_dec_and_test(r)) {
+		spin_unlock_irqrestore(lock, *flags);
+		return false;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL(refcount_dec_and_lock_irqsave);