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Subject[PATCH] spinlock.h cleanup, resend
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Linus,

This is a resend of the include/linux/spinlock.h cleanup, with the
changes you suggested.

Specifically,

- cleanup #defines: I do not follow the rationale behind the
odd line-wrapped defines at the beginning of the file. If
we have to use multiple lines, then we might as well do so
cleanly and according to normal practice...

- Remove a level of indirection: do not have spin_lock_foo
use spin_lock - just explicitly call what is needed.

- we do not need to define the spin_lock functions twice, once
for CONFIG_PREEMPT and once for !CONFIG_PREEMPT. Defining
them once with the preempt macros will optimize away fine.

- other misc. cleanup, improved comments, reordering, etc.

Patch is against 2.5.30, please apply.

Robert Love

diff -urN linux-2.5.30/include/linux/preempt.h linux/include/linux/preempt.h
--- linux-2.5.30/include/linux/preempt.h Thu Aug 1 14:16:14 2002
+++ linux/include/linux/preempt.h Thu Aug 1 15:06:28 2002
@@ -1,9 +1,14 @@
#ifndef __LINUX_PREEMPT_H
#define __LINUX_PREEMPT_H

+/*
+ * include/linux/preempt.h - macros for accessing and manipulating
+ * preempt_count (used for kernel preemption, interrupt count, etc.)
+ */
+
#include <linux/config.h>

-#define preempt_count() (current_thread_info()->preempt_count)
+#define preempt_count() (current_thread_info()->preempt_count)

#ifdef CONFIG_PREEMPT

@@ -21,23 +26,22 @@
barrier(); \
} while (0)

-#define preempt_enable() \
+#define preempt_check_resched() \
do { \
- preempt_enable_no_resched(); \
if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
preempt_schedule(); \
} while (0)

-#define preempt_check_resched() \
+#define preempt_enable() \
do { \
- if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
- preempt_schedule(); \
+ preempt_enable_no_resched(); \
+ preempt_check_resched(); \
} while (0)

#else

#define preempt_disable() do { } while (0)
-#define preempt_enable_no_resched() do {} while(0)
+#define preempt_enable_no_resched() do { } while (0)
#define preempt_enable() do { } while (0)
#define preempt_check_resched() do { } while (0)

diff -urN linux-2.5.30/include/linux/spinlock.h linux/include/linux/spinlock.h
--- linux-2.5.30/include/linux/spinlock.h Thu Aug 1 14:16:25 2002
+++ linux/include/linux/spinlock.h Thu Aug 1 15:06:28 2002
@@ -1,52 +1,23 @@
#ifndef __LINUX_SPINLOCK_H
#define __LINUX_SPINLOCK_H

+/*
+ * include/linux/spinlock.h - generic locking declarations
+ */
+
#include <linux/config.h>
#include <linux/preempt.h>
#include <linux/linkage.h>
#include <linux/compiler.h>
#include <linux/thread_info.h>
#include <linux/kernel.h>
+#include <linux/stringify.h>

#include <asm/system.h>

/*
- * These are the generic versions of the spinlocks and read-write
- * locks..
+ * Must define these before including other files, inline functions need them
*/
-#define spin_lock_irqsave(lock, flags) do { local_irq_save(flags); spin_lock(lock); } while (0)
-#define spin_lock_irq(lock) do { local_irq_disable(); spin_lock(lock); } while (0)
-#define spin_lock_bh(lock) do { local_bh_disable(); spin_lock(lock); } while (0)
-
-#define read_lock_irqsave(lock, flags) do { local_irq_save(flags); read_lock(lock); } while (0)
-#define read_lock_irq(lock) do { local_irq_disable(); read_lock(lock); } while (0)
-#define read_lock_bh(lock) do { local_bh_disable(); read_lock(lock); } while (0)
-
-#define write_lock_irqsave(lock, flags) do { local_irq_save(flags); write_lock(lock); } while (0)
-#define write_lock_irq(lock) do { local_irq_disable(); write_lock(lock); } while (0)
-#define write_lock_bh(lock) do { local_bh_disable(); write_lock(lock); } while (0)
-
-#define spin_unlock_irqrestore(lock, flags) do { _raw_spin_unlock(lock); local_irq_restore(flags); preempt_enable(); } while (0)
-#define _raw_spin_unlock_irqrestore(lock, flags) do { _raw_spin_unlock(lock); local_irq_restore(flags); } while (0)
-#define spin_unlock_irq(lock) do { _raw_spin_unlock(lock); local_irq_enable(); preempt_enable(); } while (0)
-#define spin_unlock_bh(lock) do { spin_unlock(lock); local_bh_enable(); } while (0)
-
-#define read_unlock_irqrestore(lock, flags) do { _raw_read_unlock(lock); local_irq_restore(flags); preempt_enable(); } while (0)
-#define read_unlock_irq(lock) do { _raw_read_unlock(lock); local_irq_enable(); preempt_enable(); } while (0)
-#define read_unlock_bh(lock) do { read_unlock(lock); local_bh_enable(); } while (0)
-
-#define write_unlock_irqrestore(lock, flags) do { _raw_write_unlock(lock); local_irq_restore(flags); preempt_enable(); } while (0)
-#define write_unlock_irq(lock) do { _raw_write_unlock(lock); local_irq_enable(); preempt_enable(); } while (0)
-#define write_unlock_bh(lock) do { write_unlock(lock); local_bh_enable(); } while (0)
-#define spin_trylock_bh(lock) ({ int __r; local_bh_disable();\
- __r = spin_trylock(lock); \
- if (!__r) local_bh_enable(); \
- __r; })
-
-/* Must define these before including other files, inline functions need them */
-
-#include <linux/stringify.h>
-
#define LOCK_SECTION_NAME \
".text.lock." __stringify(KBUILD_BASENAME)

@@ -60,11 +31,17 @@
#define LOCK_SECTION_END \
".previous\n\t"

+/*
+ * If CONFIG_SMP is set, pull in the _raw_* definitions
+ */
#ifdef CONFIG_SMP
#include <asm/spinlock.h>

-#elif !defined(spin_lock_init) /* !SMP and spin_lock_init not previously
- defined (e.g. by including asm/spinlock.h */
+/*
+ * !CONFIG_SMP and spin_lock_init not previously defined
+ * (e.g. by including include/asm/spinlock.h)
+ */
+#elif !defined(spin_lock_init)

#ifndef CONFIG_PREEMPT
# define atomic_dec_and_lock(atomic,lock) atomic_dec_and_test(atomic)
@@ -72,55 +49,42 @@
#endif

/*
- * Your basic spinlocks, allowing only a single CPU anywhere
- *
- * Most gcc versions have a nasty bug with empty initializers.
+ * gcc versions before ~2.95 have a nasty bug with empty initializers.
*/
#if (__GNUC__ > 2)
typedef struct { } spinlock_t;
-# define SPIN_LOCK_UNLOCKED (spinlock_t) { }
+ typedef struct { } rwlock_t;
+ #define SPIN_LOCK_UNLOCKED (spinlock_t) { }
+ #define RW_LOCK_UNLOCKED (rwlock_t) { }
#else
typedef struct { int gcc_is_buggy; } spinlock_t;
-# define SPIN_LOCK_UNLOCKED (spinlock_t) { 0 }
+ typedef struct { int gcc_is_buggy; } rwlock_t;
+ #define SPIN_LOCK_UNLOCKED (spinlock_t) { 0 }
+ #define RW_LOCK_UNLOCKED (rwlock_t) { 0 }
#endif

+/*
+ * If CONFIG_SMP is unset, declare the _raw_* definitions as nops
+ */
#define spin_lock_init(lock) do { (void)(lock); } while(0)
-#define _raw_spin_lock(lock) (void)(lock) /* Not "unused variable". */
+#define _raw_spin_lock(lock) (void)(lock)
#define spin_is_locked(lock) ((void)(lock), 0)
#define _raw_spin_trylock(lock) ((void)(lock), 1)
#define spin_unlock_wait(lock) do { (void)(lock); } while(0)
#define _raw_spin_unlock(lock) do { (void)(lock); } while(0)
-
-/*
- * Read-write spinlocks, allowing multiple readers
- * but only one writer.
- *
- * NOTE! it is quite common to have readers in interrupts
- * but no interrupt writers. For those circumstances we
- * can "mix" irq-safe locks - any writer needs to get a
- * irq-safe write-lock, but readers can get non-irqsafe
- * read-locks.
- *
- * Most gcc versions have a nasty bug with empty initializers.
- */
-#if (__GNUC__ > 2)
- typedef struct { } rwlock_t;
- #define RW_LOCK_UNLOCKED (rwlock_t) { }
-#else
- typedef struct { int gcc_is_buggy; } rwlock_t;
- #define RW_LOCK_UNLOCKED (rwlock_t) { 0 }
-#endif
-
#define rwlock_init(lock) do { } while(0)
-#define _raw_read_lock(lock) (void)(lock) /* Not "unused variable". */
+#define _raw_read_lock(lock) (void)(lock)
#define _raw_read_unlock(lock) do { } while(0)
-#define _raw_write_lock(lock) (void)(lock) /* Not "unused variable". */
+#define _raw_write_lock(lock) (void)(lock)
#define _raw_write_unlock(lock) do { } while(0)

#endif /* !SMP */

-#ifdef CONFIG_PREEMPT
-
+/*
+ * Define the various spin_lock and rw_lock methods. Note we define these
+ * regardless of whether CONFIG_SMP or CONFIG_PREEMPT are set. The various
+ * methods are defined as nops in the case they are not required.
+ */
#define spin_lock(lock) \
do { \
preempt_disable(); \
@@ -129,31 +93,175 @@

#define spin_trylock(lock) ({preempt_disable(); _raw_spin_trylock(lock) ? \
1 : ({preempt_enable(); 0;});})
+
#define spin_unlock(lock) \
do { \
_raw_spin_unlock(lock); \
preempt_enable(); \
} while (0)

-#define read_lock(lock) ({preempt_disable(); _raw_read_lock(lock);})
-#define read_unlock(lock) ({_raw_read_unlock(lock); preempt_enable();})
-#define write_lock(lock) ({preempt_disable(); _raw_write_lock(lock);})
-#define write_unlock(lock) ({_raw_write_unlock(lock); preempt_enable();})
+#define read_lock(lock) \
+do { \
+ preempt_disable(); \
+ _raw_read_lock(lock); \
+} while(0)
+
+#define read_unlock(lock) \
+do { \
+ _raw_read_unlock(lock); \
+ preempt_enable(); \
+} while(0)
+
+#define write_lock(lock) \
+do { \
+ preempt_disable(); \
+ _raw_write_lock(lock); \
+} while(0)
+
+#define write_unlock(lock) \
+do { \
+ _raw_write_unlock(lock); \
+ preempt_enable(); \
+} while(0)
+
#define write_trylock(lock) ({preempt_disable();_raw_write_trylock(lock) ? \
1 : ({preempt_enable(); 0;});})

-#else
+#define spin_lock_irqsave(lock, flags) \
+do { \
+ local_irq_save(flags); \
+ preempt_disable(); \
+ _raw_spin_lock(lock); \
+} while (0)

-#define spin_lock(lock) _raw_spin_lock(lock)
-#define spin_trylock(lock) _raw_spin_trylock(lock)
-#define spin_unlock(lock) _raw_spin_unlock(lock)
-
-#define read_lock(lock) _raw_read_lock(lock)
-#define read_unlock(lock) _raw_read_unlock(lock)
-#define write_lock(lock) _raw_write_lock(lock)
-#define write_unlock(lock) _raw_write_unlock(lock)
-#define write_trylock(lock) _raw_write_trylock(lock)
-#endif
+#define spin_lock_irq(lock) \
+do { \
+ local_irq_disable(); \
+ preempt_disable(); \
+ _raw_spin_lock(lock); \
+} while (0)
+
+#define spin_lock_bh(lock) \
+do { \
+ local_bh_disable(); \
+ preempt_disable(); \
+ _raw_spin_lock(lock); \
+} while (0)
+
+#define read_lock_irqsave(lock, flags) \
+do { \
+ local_irq_save(flags); \
+ preempt_disable(); \
+ _raw_read_lock(lock); \
+} while (0)
+
+#define read_lock_irq(lock) \
+do { \
+ local_irq_disable(); \
+ preempt_disable(); \
+ _raw_read_lock(lock); \
+} while (0)
+
+#define read_lock_bh(lock) \
+do { \
+ local_bh_disable(); \
+ preempt_disable(); \
+ _raw_read_lock(lock); \
+} while (0)
+
+#define write_lock_irqsave(lock, flags) \
+do { \
+ local_irq_save(flags); \
+ preempt_disable(); \
+ _raw_write_lock(lock); \
+} while (0)
+
+#define write_lock_irq(lock) \
+do { \
+ local_irq_disable(); \
+ preempt_disable(); \
+ _raw_write_lock(lock); \
+} while (0)
+
+#define write_lock_bh(lock) \
+do { \
+ local_bh_disable(); \
+ preempt_disable(); \
+ _raw_write_lock(lock); \
+} while (0)
+
+#define spin_unlock_irqrestore(lock, flags) \
+do { \
+ _raw_spin_unlock(lock); \
+ local_irq_restore(flags); \
+ preempt_enable(); \
+} while (0)
+
+#define _raw_spin_unlock_irqrestore(lock, flags) \
+do { \
+ _raw_spin_unlock(lock); \
+ local_irq_restore(flags); \
+} while (0)
+
+#define spin_unlock_irq(lock) \
+do { \
+ _raw_spin_unlock(lock); \
+ local_irq_enable(); \
+ preempt_enable(); \
+} while (0)
+
+#define spin_unlock_bh(lock) \
+do { \
+ _raw_spin_unlock(lock); \
+ preempt_enable(); \
+ local_bh_enable(); \
+} while (0)
+
+#define read_unlock_irqrestore(lock, flags) \
+do { \
+ _raw_read_unlock(lock); \
+ local_irq_restore(flags); \
+ preempt_enable(); \
+} while (0)
+
+#define read_unlock_irq(lock) \
+do { \
+ _raw_read_unlock(lock); \
+ local_irq_enable(); \
+ preempt_enable(); \
+} while (0)
+
+#define read_unlock_bh(lock) \
+do { \
+ _raw_read_unlock(lock); \
+ preempt_enable(); \
+ local_bh_enable(); \
+} while (0)
+
+#define write_unlock_irqrestore(lock, flags) \
+do { \
+ _raw_write_unlock(lock); \
+ local_irq_restore(flags); \
+ preempt_enable(); \
+} while (0)
+
+#define write_unlock_irq(lock) \
+do { \
+ _raw_write_unlock(lock); \
+ local_irq_enable(); \
+ preempt_enable(); \
+} while (0)
+
+#define write_unlock_bh(lock) \
+do { \
+ _raw_write_unlock(lock); \
+ preempt_enable(); \
+ local_bh_enable(); \
+} while (0)
+
+#define spin_trylock_bh(lock) ({ local_bh_disable(); preempt_disable(); \
+ _raw_spin_trylock(lock) ? 1 : \
+ ({preempt_enable(); local_bh_enable(); 0;});})

/* "lock on reference count zero" */
#ifndef ATOMIC_DEC_AND_LOCK
-
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