[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>
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 @@
"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"
+ :"=m" (lock->slock) : : "memory"
-
-static inline void _raw_spin_unlock(spinlock_t *lock)
+static inline void __raw_spin_lock(raw_spinlock_t *lock)
{
-#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");
}
-#else
+#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
-#define spin_unlock_string \
- "xchgb %b0, %1" \
- :"=q" (oldval), "=m" (lock->lock) \
- :"0" (oldval) : "memory"
-
-static inline void _raw_spin_unlock(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
- );
-}
-
-#endif
-
-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 @@
* 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 @@
*
* 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 @@
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 @@
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 */