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, 116 deletions

diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile
index 4d3e38392cb1..ce144b67f060 100644
--- a/arch/s390/kernel/Makefile
+++ b/arch/s390/kernel/Makefile
@@ -11,7 +11,7 @@ CFLAGS_smp.o	:= -Wno-nonnull
 
 obj-y	:=  bitmap.o traps.o time.o process.o base.o early.o \
             setup.o sys_s390.o ptrace.o signal.o cpcmd.o ebcdic.o \
-	    semaphore.o s390_ext.o debug.o irq.o ipl.o dis.o diag.o
+	    s390_ext.o debug.o irq.o ipl.o dis.o diag.o
 
 obj-y	+= $(if $(CONFIG_64BIT),entry64.o,entry.o)
 obj-y	+= $(if $(CONFIG_64BIT),reipl64.o,reipl.o)
diff --git a/arch/s390/kernel/s390_ksyms.c b/arch/s390/kernel/s390_ksyms.c
index 7234c737f825..48238a114ce9 100644
--- a/arch/s390/kernel/s390_ksyms.c
+++ b/arch/s390/kernel/s390_ksyms.c
@@ -27,13 +27,6 @@ EXPORT_SYMBOL(_zb_findmap);
 EXPORT_SYMBOL(_sb_findmap);
 
 /*
- * semaphore ops
- */
-EXPORT_SYMBOL(__up);
-EXPORT_SYMBOL(__down);
-EXPORT_SYMBOL(__down_interruptible);
-
-/*
  * binfmt_elf loader 
  */
 extern int dump_fpu (struct pt_regs * regs, s390_fp_regs *fpregs);
diff --git a/arch/s390/kernel/semaphore.c b/arch/s390/kernel/semaphore.c
deleted file mode 100644
index 191303f6c1d8..000000000000
--- a/arch/s390/kernel/semaphore.c
+++ /dev/null
@@ -1,108 +0,0 @@
-/*
- *  linux/arch/s390/kernel/semaphore.c
- *
- *  S390 version
- *    Copyright (C) 1998-2000 IBM Corporation
- *    Author(s): Martin Schwidefsky
- *
- *  Derived from "linux/arch/i386/kernel/semaphore.c
- *    Copyright (C) 1999, Linus Torvalds
- *
- */
-#include <linux/sched.h>
-#include <linux/errno.h>
-#include <linux/init.h>
-
-#include <asm/semaphore.h>
-
-/*
- * Atomically update sem->count. Equivalent to:
- *   old_val = sem->count.counter;
- *   new_val = ((old_val >= 0) ? old_val : 0) + incr;
- *   sem->count.counter = new_val;
- *   return old_val;
- */
-static inline int __sem_update_count(struct semaphore *sem, int incr)
-{
-	int old_val, new_val;
-
-	asm volatile(
-		"	l	%0,0(%3)\n"
-		"0:	ltr	%1,%0\n"
-		"	jhe	1f\n"
-		"	lhi	%1,0\n"
-		"1:	ar	%1,%4\n"
-		"	cs	%0,%1,0(%3)\n"
-		"	jl	0b\n"
-		: "=&d" (old_val), "=&d" (new_val), "=m" (sem->count)
-		: "a" (&sem->count), "d" (incr), "m" (sem->count)
-		: "cc");
-	return old_val;
-}
-
-/*
- * The inline function up() incremented count but the result
- * was <= 0. This indicates that some process is waiting on
- * the semaphore. The semaphore is free and we'll wake the
- * first sleeping process, so we set count to 1 unless some
- * other cpu has called up in the meantime in which case
- * we just increment count by 1.
- */
-void __up(struct semaphore *sem)
-{
-	__sem_update_count(sem, 1);
-	wake_up(&sem->wait);
-}
-
-/*
- * The inline function down() decremented count and the result
- * was < 0. The wait loop will atomically test and update the
- * semaphore counter following the rules:
- *   count > 0: decrement count, wake up queue and exit.
- *   count <= 0: set count to -1, go to sleep.
- */
-void __sched __down(struct semaphore * sem)
-{
-	struct task_struct *tsk = current;
-	DECLARE_WAITQUEUE(wait, tsk);
-
-	__set_task_state(tsk, TASK_UNINTERRUPTIBLE);
-	add_wait_queue_exclusive(&sem->wait, &wait);
-	while (__sem_update_count(sem, -1) <= 0) {
-		schedule();
-		set_task_state(tsk, TASK_UNINTERRUPTIBLE);
-	}
-	remove_wait_queue(&sem->wait, &wait);
-	__set_task_state(tsk, TASK_RUNNING);
-	wake_up(&sem->wait);
-}
-
-/*
- * Same as __down() with an additional test for signals.
- * If a signal is pending the count is updated as follows:
- *   count > 0: wake up queue and exit.
- *   count <= 0: set count to 0, wake up queue and exit.
- */
-int __sched __down_interruptible(struct semaphore * sem)
-{
-	int retval = 0;
-	struct task_struct *tsk = current;
-	DECLARE_WAITQUEUE(wait, tsk);
-
-	__set_task_state(tsk, 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();
-		set_task_state(tsk, TASK_INTERRUPTIBLE);
-	}
-	remove_wait_queue(&sem->wait, &wait);
-	__set_task_state(tsk, TASK_RUNNING);
-	wake_up(&sem->wait);
-	return retval;
-}
-