Generic semaphore implementation

Semaphores are no longer performance-critical, so a generic C
implementation is better for maintainability, debuggability and
extensibility.  Thanks to Peter Zijlstra for fixing the lockdep
warning.  Thanks to Harvey Harrison for pointing out that the
unlikely() was unnecessary.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 1 insertions, 261 deletions

diff --git a/arch/sparc64/kernel/Makefile b/arch/sparc64/kernel/Makefile
index 1bf5b187de4..459462e80a1 100644
--- a/arch/sparc64/kernel/Makefile
+++ b/arch/sparc64/kernel/Makefile
@@ -10,7 +10,7 @@ extra-y		:= head.o init_task.o vmlinux.lds
 obj-y		:= process.o setup.o cpu.o idprom.o \
 		   traps.o auxio.o una_asm.o sysfs.o iommu.o \
 		   irq.o ptrace.o time.o sys_sparc.o signal.o \
-		   unaligned.o central.o pci.o starfire.o semaphore.o \
+		   unaligned.o central.o pci.o starfire.o \
 		   power.o sbus.o sparc64_ksyms.o chmc.o \
 		   visemul.o prom.o of_device.o hvapi.o sstate.o mdesc.o
 
diff --git a/arch/sparc64/kernel/semaphore.c b/arch/sparc64/kernel/semaphore.c
deleted file mode 100644
index 9974a689955..00000000000
--- a/arch/sparc64/kernel/semaphore.c
+++ /dev/null
@@ -1,254 +0,0 @@
-/* semaphore.c: Sparc64 semaphore implementation.
- *
- * This is basically the PPC semaphore scheme ported to use
- * the sparc64 atomic instructions, so see the PPC code for
- * credits.
- */
-
-#include <linux/sched.h>
-#include <linux/errno.h>
-#include <linux/init.h>
-
-/*
- * Atomically update sem->count.
- * This does the equivalent of the following:
- *
- *	old_count = sem->count;
- *	tmp = MAX(old_count, 0) + incr;
- *	sem->count = tmp;
- *	return old_count;
- */
-static inline int __sem_update_count(struct semaphore *sem, int incr)
-{
-	int old_count, tmp;
-
-	__asm__ __volatile__("\n"
-"	! __sem_update_count old_count(%0) tmp(%1) incr(%4) &sem->count(%3)\n"
-"1:	ldsw	[%3], %0\n"
-"	mov	%0, %1\n"
-"	cmp	%0, 0\n"
-"	movl	%%icc, 0, %1\n"
-"	add	%1, %4, %1\n"
-"	cas	[%3], %0, %1\n"
-"	cmp	%0, %1\n"
-"	membar	#StoreLoad | #StoreStore\n"
-"	bne,pn	%%icc, 1b\n"
-"	 nop\n"
-	: "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
-	: "r" (&sem->count), "r" (incr), "m" (sem->count)
-	: "cc");
-
-	return old_count;
-}
-
-static void __up(struct semaphore *sem)
-{
-	__sem_update_count(sem, 1);
-	wake_up(&sem->wait);
-}
-
-void up(struct semaphore *sem)
-{
-	/* This atomically does:
-	 * 	old_val = sem->count;
-	 *	new_val = sem->count + 1;
-	 *	sem->count = new_val;
-	 *	if (old_val < 0)
-	 *		__up(sem);
-	 *
-	 * The (old_val < 0) test is equivalent to
-	 * the more straightforward (new_val <= 0),
-	 * but it is easier to test the former because
-	 * of how the CAS instruction works.
-	 */
-
-	__asm__ __volatile__("\n"
-"	! up sem(%0)\n"
-"	membar	#StoreLoad | #LoadLoad\n"
-"1:	lduw	[%0], %%g1\n"
-"	add	%%g1, 1, %%g7\n"
-"	cas	[%0], %%g1, %%g7\n"
-"	cmp	%%g1, %%g7\n"
-"	bne,pn	%%icc, 1b\n"
-"	 addcc	%%g7, 1, %%g0\n"
-"	membar	#StoreLoad | #StoreStore\n"
-"	ble,pn	%%icc, 3f\n"
-"	 nop\n"
-"2:\n"
-"	.subsection 2\n"
-"3:	mov	%0, %%g1\n"
-"	save	%%sp, -160, %%sp\n"
-"	call	%1\n"
-"	 mov	%%g1, %%o0\n"
-"	ba,pt	%%xcc, 2b\n"
-"	 restore\n"
-"	.previous\n"
-	: : "r" (sem), "i" (__up)
-	: "g1", "g2", "g3", "g7", "memory", "cc");
-}
-
-static void __sched __down(struct semaphore * sem)
-{
-	struct task_struct *tsk = current;
-	DECLARE_WAITQUEUE(wait, tsk);
-
-	tsk->state = TASK_UNINTERRUPTIBLE;
-	add_wait_queue_exclusive(&sem->wait, &wait);
-
-	while (__sem_update_count(sem, -1) <= 0) {
-		schedule();
-		tsk->state = TASK_UNINTERRUPTIBLE;
-	}
-	remove_wait_queue(&sem->wait, &wait);
-	tsk->state = TASK_RUNNING;
-
-	wake_up(&sem->wait);
-}
-
-void __sched down(struct semaphore *sem)
-{
-	might_sleep();
-	/* This atomically does:
-	 * 	old_val = sem->count;
-	 *	new_val = sem->count - 1;
-	 *	sem->count = new_val;
-	 *	if (old_val < 1)
-	 *		__down(sem);
-	 *
-	 * The (old_val < 1) test is equivalent to
-	 * the more straightforward (new_val < 0),
-	 * but it is easier to test the former because
-	 * of how the CAS instruction works.
-	 */
-
-	__asm__ __volatile__("\n"
-"	! down sem(%0)\n"
-"1:	lduw	[%0], %%g1\n"
-"	sub	%%g1, 1, %%g7\n"
-"	cas	[%0], %%g1, %%g7\n"
-"	cmp	%%g1, %%g7\n"
-"	bne,pn	%%icc, 1b\n"
-"	 cmp	%%g7, 1\n"
-"	membar	#StoreLoad | #StoreStore\n"
-"	bl,pn	%%icc, 3f\n"
-"	 nop\n"
-"2:\n"
-"	.subsection 2\n"
-"3:	mov	%0, %%g1\n"
-"	save	%%sp, -160, %%sp\n"
-"	call	%1\n"
-"	 mov	%%g1, %%o0\n"
-"	ba,pt	%%xcc, 2b\n"
-"	 restore\n"
-"	.previous\n"
-	: : "r" (sem), "i" (__down)
-	: "g1", "g2", "g3", "g7", "memory", "cc");
-}
-
-int down_trylock(struct semaphore *sem)
-{
-	int ret;
-
-	/* This atomically does:
-	 * 	old_val = sem->count;
-	 *	new_val = sem->count - 1;
-	 *	if (old_val < 1) {
-	 *		ret = 1;
-	 *	} else {
-	 *		sem->count = new_val;
-	 *		ret = 0;
-	 *	}
-	 *
-	 * The (old_val < 1) test is equivalent to
-	 * the more straightforward (new_val < 0),
-	 * but it is easier to test the former because
-	 * of how the CAS instruction works.
-	 */
-
-	__asm__ __volatile__("\n"
-"	! down_trylock sem(%1) ret(%0)\n"
-"1:	lduw	[%1], %%g1\n"
-"	sub	%%g1, 1, %%g7\n"
-"	cmp	%%g1, 1\n"
-"	bl,pn	%%icc, 2f\n"
-"	 mov	1, %0\n"
-"	cas	[%1], %%g1, %%g7\n"
-"	cmp	%%g1, %%g7\n"
-"	bne,pn	%%icc, 1b\n"
-"	 mov	0, %0\n"
-"	membar	#StoreLoad | #StoreStore\n"
-"2:\n"
-	: "=&r" (ret)
-	: "r" (sem)
-	: "g1", "g7", "memory", "cc");
-
-	return ret;
-}
-
-static int __sched __down_interruptible(struct semaphore * sem)
-{
-	int retval = 0;
-	struct task_struct *tsk = current;
-	DECLARE_WAITQUEUE(wait, tsk);
-
-	tsk->state = TASK_INTERRUPTIBLE;
-	add_wait_queue_exclusive(&sem->wait, &wait);
-
-	while (__sem_update_count(sem, -1) <= 0) {
-		if (signal_pending(current)) {
-			__sem_update_count(sem, 0);
-			retval = -EINTR;
-			break;
-		}
-		schedule();
-		tsk->state = TASK_INTERRUPTIBLE;
-	}
-	tsk->state = TASK_RUNNING;
-	remove_wait_queue(&sem->wait, &wait);
-	wake_up(&sem->wait);
-	return retval;
-}
-
-int __sched down_interruptible(struct semaphore *sem)
-{
-	int ret = 0;
-	
-	might_sleep();
-	/* This atomically does:
-	 * 	old_val = sem->count;
-	 *	new_val = sem->count - 1;
-	 *	sem->count = new_val;
-	 *	if (old_val < 1)
-	 *		ret = __down_interruptible(sem);
-	 *
-	 * The (old_val < 1) test is equivalent to
-	 * the more straightforward (new_val < 0),
-	 * but it is easier to test the former because
-	 * of how the CAS instruction works.
-	 */
-
-	__asm__ __volatile__("\n"
-"	! down_interruptible sem(%2) ret(%0)\n"
-"1:	lduw	[%2], %%g1\n"
-"	sub	%%g1, 1, %%g7\n"
-"	cas	[%2], %%g1, %%g7\n"
-"	cmp	%%g1, %%g7\n"
-"	bne,pn	%%icc, 1b\n"
-"	 cmp	%%g7, 1\n"
-"	membar	#StoreLoad | #StoreStore\n"
-"	bl,pn	%%icc, 3f\n"
-"	 nop\n"
-"2:\n"
-"	.subsection 2\n"
-"3:	mov	%2, %%g1\n"
-"	save	%%sp, -160, %%sp\n"
-"	call	%3\n"
-"	 mov	%%g1, %%o0\n"
-"	ba,pt	%%xcc, 2b\n"
-"	 restore\n"
-"	.previous\n"
-	: "=r" (ret)
-	: "0" (ret), "r" (sem), "i" (__down_interruptible)
-	: "g1", "g2", "g3", "g7", "memory", "cc");
-	return ret;
-}
diff --git a/arch/sparc64/kernel/sparc64_ksyms.c b/arch/sparc64/kernel/sparc64_ksyms.c
index 51fa773f38c..051b8d9cb98 100644
--- a/arch/sparc64/kernel/sparc64_ksyms.c
+++ b/arch/sparc64/kernel/sparc64_ksyms.c
@@ -130,12 +130,6 @@ EXPORT_SYMBOL(_mcount);
 
 EXPORT_SYMBOL(sparc64_get_clock_tick);
 
-/* semaphores */
-EXPORT_SYMBOL(down);
-EXPORT_SYMBOL(down_trylock);
-EXPORT_SYMBOL(down_interruptible);
-EXPORT_SYMBOL(up);
-
 /* RW semaphores */
 EXPORT_SYMBOL(__down_read);
 EXPORT_SYMBOL(__down_read_trylock);