[PATCH] spinlock consolidation

This patch (written by me and also containing many suggestions of Arjan van
de Ven) does a major cleanup of the spinlock code.  It does the following
things:

 - consolidates and enhances the spinlock/rwlock debugging code

 - simplifies the asm/spinlock.h files

 - encapsulates the raw spinlock type and moves generic spinlock
   features (such as ->break_lock) into the generic code.

 - cleans up the spinlock code hierarchy to get rid of the spaghetti.

Most notably there's now only a single variant of the debugging code,
located in lib/spinlock_debug.c.  (previously we had one SMP debugging
variant per architecture, plus a separate generic one for UP builds)

Also, i've enhanced the rwlock debugging facility, it will now track
write-owners.  There is new spinlock-owner/CPU-tracking on SMP builds too.
All locks have lockup detection now, which will work for both soft and hard
spin/rwlock lockups.

The arch-level include files now only contain the minimally necessary
subset of the spinlock code - all the rest that can be generalized now
lives in the generic headers:

 include/asm-i386/spinlock_types.h       |   16
 include/asm-x86_64/spinlock_types.h     |   16

I have also split up the various spinlock variants into separate files,
making it easier to see which does what. The new layout is:

   SMP                         |  UP
   ----------------------------|-----------------------------------
   asm/spinlock_types_smp.h    |  linux/spinlock_types_up.h
   linux/spinlock_types.h      |  linux/spinlock_types.h
   asm/spinlock_smp.h          |  linux/spinlock_up.h
   linux/spinlock_api_smp.h    |  linux/spinlock_api_up.h
   linux/spinlock.h            |  linux/spinlock.h

/*
 * here's the role of the various spinlock/rwlock related include files:
 *
 * on SMP builds:
 *
 *  asm/spinlock_types.h: contains the raw_spinlock_t/raw_rwlock_t and the
 *                        initializers
 *
 *  linux/spinlock_types.h:
 *                        defines the generic type and initializers
 *
 *  asm/spinlock.h:       contains the __raw_spin_*()/etc. lowlevel
 *                        implementations, mostly inline assembly code
 *
 *   (also included on UP-debug builds:)
 *
 *  linux/spinlock_api_smp.h:
 *                        contains the prototypes for the _spin_*() APIs.
 *
 *  linux/spinlock.h:     builds the final spin_*() APIs.
 *
 * on UP builds:
 *
 *  linux/spinlock_type_up.h:
 *                        contains the generic, simplified UP spinlock type.
 *                        (which is an empty structure on non-debug builds)
 *
 *  linux/spinlock_types.h:
 *                        defines the generic type and initializers
 *
 *  linux/spinlock_up.h:
 *                        contains the __raw_spin_*()/etc. version of UP
 *                        builds. (which are NOPs on non-debug, non-preempt
 *                        builds)
 *
 *   (included on UP-non-debug builds:)
 *
 *  linux/spinlock_api_up.h:
 *                        builds the _spin_*() APIs.
 *
 *  linux/spinlock.h:     builds the final spin_*() APIs.
 */

All SMP and UP architectures are converted by this patch.

arm, i386, ia64, ppc, ppc64, s390/s390x, x64 was build-tested via
crosscompilers.  m32r, mips, sh, sparc, have not been tested yet, but should
be mostly fine.

From: Grant Grundler <grundler@parisc-linux.org>

  Booted and lightly tested on a500-44 (64-bit, SMP kernel, dual CPU).
  Builds 32-bit SMP kernel (not booted or tested).  I did not try to build
  non-SMP kernels.  That should be trivial to fix up later if necessary.

  I converted bit ops atomic_hash lock to raw_spinlock_t.  Doing so avoids
  some ugly nesting of linux/*.h and asm/*.h files.  Those particular locks
  are well tested and contained entirely inside arch specific code.  I do NOT
  expect any new issues to arise with them.

 If someone does ever need to use debug/metrics with them, then they will
  need to unravel this hairball between spinlocks, atomic ops, and bit ops
  that exist only because parisc has exactly one atomic instruction: LDCW
  (load and clear word).

From: "Luck, Tony" <tony.luck@intel.com>

   ia64 fix

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjanv@infradead.org>
Signed-off-by: Grant Grundler <grundler@parisc-linux.org>
Cc: Matthew Wilcox <willy@debian.org>
Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Mikael Pettersson <mikpe@csd.uu.se>
Signed-off-by: Benoit Boissinot <benoit.boissinot@ens-lyon.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 42 insertions, 122 deletions

diff --git a/include/asm-x86_64/spinlock.h b/include/asm-x86_64/spinlock.h
index 5aeb57a..6963683 100644
--- a/include/asm-x86_64/spinlock.h
+++ b/include/asm-x86_64/spinlock.h
@@ -6,47 +6,21 @@
 #include <asm/page.h>
 #include <linux/config.h>
 
-extern int printk(const char * fmt, ...)
-	__attribute__ ((format (printf, 1, 2)));
-
 /*
  * Your basic SMP spinlocks, allowing only a single CPU anywhere
- */
-
-typedef struct {
-	volatile unsigned int lock;
-#ifdef CONFIG_DEBUG_SPINLOCK
-	unsigned magic;
-#endif
-#ifdef CONFIG_PREEMPT
-	unsigned int break_lock;
-#endif
-} spinlock_t;
-
-#define SPINLOCK_MAGIC	0xdead4ead
-
-#ifdef CONFIG_DEBUG_SPINLOCK
-#define SPINLOCK_MAGIC_INIT	, SPINLOCK_MAGIC
-#else
-#define SPINLOCK_MAGIC_INIT	/* */
-#endif
-
-#define SPIN_LOCK_UNLOCKED (spinlock_t) { 1 SPINLOCK_MAGIC_INIT }
-
-#define spin_lock_init(x)	do { *(x) = SPIN_LOCK_UNLOCKED; } while(0)
-
-/*
+ *
  * Simple spin lock operations.  There are two variants, one clears IRQ's
  * on the local processor, one does not.
  *
  * We make no fairness assumptions. They have a cost.
+ *
+ * (the type definitions are in asm/spinlock_types.h)
  */
 
-#define spin_is_locked(x)	(*(volatile signed char *)(&(x)->lock) <= 0)
-#define spin_unlock_wait(x)	do { barrier(); } while(spin_is_locked(x))
-#define _raw_spin_lock_flags(lock, flags) _raw_spin_lock(lock)
+#define __raw_spin_is_locked(x) \
+		(*(volatile signed char *)(&(x)->slock) <= 0)
 
-#define spin_lock_string \
+#define __raw_spin_lock_string \
 	"\n1:\t" \
 	"lock ; decb %0\n\t" \
 	"js 2f\n" \
@@ -58,74 +32,40 @@ typedef struct {
 	"jmp 1b\n" \
 	LOCK_SECTION_END
 
-/*
- * This works. Despite all the confusion.
- * (except on PPro SMP or if we are using OOSTORE)
- * (PPro errata 66, 92)
- */
- 
-#if !defined(CONFIG_X86_OOSTORE) && !defined(CONFIG_X86_PPRO_FENCE)
-
-#define spin_unlock_string \
+#define __raw_spin_unlock_string \
 	"movb $1,%0" \
-		:"=m" (lock->lock) : : "memory"
-
-
-static inline void _raw_spin_unlock(spinlock_t *lock)
-{
-#ifdef CONFIG_DEBUG_SPINLOCK
-	BUG_ON(lock->magic != SPINLOCK_MAGIC);
-	assert_spin_locked(lock);
-#endif
-	__asm__ __volatile__(
-		spin_unlock_string
-	);
-}
-
-#else
-
-#define spin_unlock_string \
-	"xchgb %b0, %1" \
-		:"=q" (oldval), "=m" (lock->lock) \
-		:"0" (oldval) : "memory"
+		:"=m" (lock->slock) : : "memory"
 
-static inline void _raw_spin_unlock(spinlock_t *lock)
+static inline void __raw_spin_lock(raw_spinlock_t *lock)
 {
-	char oldval = 1;
-#ifdef CONFIG_DEBUG_SPINLOCK
-	BUG_ON(lock->magic != SPINLOCK_MAGIC);
-	assert_spin_locked(lock);
-#endif
 	__asm__ __volatile__(
-		spin_unlock_string
-	);
+		__raw_spin_lock_string
+		:"=m" (lock->slock) : : "memory");
 }
 
-#endif
+#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
 
-static inline int _raw_spin_trylock(spinlock_t *lock)
+static inline int __raw_spin_trylock(raw_spinlock_t *lock)
 {
 	char oldval;
+
 	__asm__ __volatile__(
 		"xchgb %b0,%1"
-		:"=q" (oldval), "=m" (lock->lock)
+		:"=q" (oldval), "=m" (lock->slock)
 		:"0" (0) : "memory");
+
 	return oldval > 0;
 }
 
-static inline void _raw_spin_lock(spinlock_t *lock)
+static inline void __raw_spin_unlock(raw_spinlock_t *lock)
 {
-#ifdef CONFIG_DEBUG_SPINLOCK
-	if (lock->magic != SPINLOCK_MAGIC) {
-		printk("eip: %p\n", __builtin_return_address(0));
-		BUG();
-	}
-#endif
 	__asm__ __volatile__(
-		spin_lock_string
-		:"=m" (lock->lock) : : "memory");
+		__raw_spin_unlock_string
+	);
 }
 
+#define __raw_spin_unlock_wait(lock) \
+	do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
 
 /*
  * Read-write spinlocks, allowing multiple readers
@@ -136,33 +76,7 @@ static inline void _raw_spin_lock(spinlock_t *lock)
  * can "mix" irq-safe locks - any writer needs to get a
  * irq-safe write-lock, but readers can get non-irqsafe
  * read-locks.
- */
-typedef struct {
-	volatile unsigned int lock;
-#ifdef CONFIG_DEBUG_SPINLOCK
-	unsigned magic;
-#endif
-#ifdef CONFIG_PREEMPT
-	unsigned int break_lock;
-#endif
-} rwlock_t;
-
-#define RWLOCK_MAGIC	0xdeaf1eed
-
-#ifdef CONFIG_DEBUG_SPINLOCK
-#define RWLOCK_MAGIC_INIT	, RWLOCK_MAGIC
-#else
-#define RWLOCK_MAGIC_INIT	/* */
-#endif
-
-#define RW_LOCK_UNLOCKED (rwlock_t) { RW_LOCK_BIAS RWLOCK_MAGIC_INIT }
-
-#define rwlock_init(x)	do { *(x) = RW_LOCK_UNLOCKED; } while(0)
-
-#define read_can_lock(x)	((int)(x)->lock > 0)
-#define write_can_lock(x)	((x)->lock == RW_LOCK_BIAS)
-
-/*
+ *
  * On x86, we implement read-write locks as a 32-bit counter
  * with the high bit (sign) being the "contended" bit.
  *
@@ -170,29 +84,24 @@ typedef struct {
  *
  * Changed to use the same technique as rw semaphores.  See
  * semaphore.h for details.  -ben
+ *
+ * the helpers are in arch/i386/kernel/semaphore.c
  */
-/* the spinlock helpers are in arch/i386/kernel/semaphore.c */
 
-static inline void _raw_read_lock(rwlock_t *rw)
+#define __raw_read_can_lock(x)		((int)(x)->lock > 0)
+#define __raw_write_can_lock(x)		((x)->lock == RW_LOCK_BIAS)
+
+static inline void __raw_read_lock(raw_rwlock_t *rw)
 {
-#ifdef CONFIG_DEBUG_SPINLOCK
-	BUG_ON(rw->magic != RWLOCK_MAGIC);
-#endif
 	__build_read_lock(rw, "__read_lock_failed");
 }
 
-static inline void _raw_write_lock(rwlock_t *rw)
+static inline void __raw_write_lock(raw_rwlock_t *rw)
 {
-#ifdef CONFIG_DEBUG_SPINLOCK
-	BUG_ON(rw->magic != RWLOCK_MAGIC);
-#endif
 	__build_write_lock(rw, "__write_lock_failed");
 }
 
-#define _raw_read_unlock(rw)		asm volatile("lock ; incl %0" :"=m" ((rw)->lock) : : "memory")
-#define _raw_write_unlock(rw)	asm volatile("lock ; addl $" RW_LOCK_BIAS_STR ",%0":"=m" ((rw)->lock) : : "memory")
-
-static inline int _raw_read_trylock(rwlock_t *lock)
+static inline int __raw_read_trylock(raw_rwlock_t *lock)
 {
 	atomic_t *count = (atomic_t *)lock;
 	atomic_dec(count);
@@ -202,7 +111,7 @@ static inline int _raw_read_trylock(rwlock_t *lock)
 	return 0;
 }
 
-static inline int _raw_write_trylock(rwlock_t *lock)
+static inline int __raw_write_trylock(raw_rwlock_t *lock)
 {
 	atomic_t *count = (atomic_t *)lock;
 	if (atomic_sub_and_test(RW_LOCK_BIAS, count))
@@ -211,4 +120,15 @@ static inline int _raw_write_trylock(rwlock_t *lock)
 	return 0;
 }
 
+static inline void __raw_read_unlock(raw_rwlock_t *rw)
+{
+	asm volatile("lock ; incl %0" :"=m" (rw->lock) : : "memory");
+}
+
+static inline void __raw_write_unlock(raw_rwlock_t *rw)
+{
+	asm volatile("lock ; addl $" RW_LOCK_BIAS_STR ",%0"
+				: "=m" (rw->lock) : : "memory");
+}
+
 #endif /* __ASM_SPINLOCK_H */