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, 137 deletions

diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index c1baf9d5903f..b9dbfff9afe9 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -12,7 +12,7 @@ CFLAGS_prom_init.o      += -fPIC
 CFLAGS_btext.o          += -fPIC
 endif
 
-obj-y                           := semaphore.o cputable.o ptrace.o syscalls.o \
+obj-y                           := cputable.o ptrace.o syscalls.o \
                                    irq.o align.o signal_32.o pmc.o vdso.o \
                                    init_task.o process.o systbl.o idle.o \
                                    signal.o
diff --git a/arch/powerpc/kernel/ppc_ksyms.c b/arch/powerpc/kernel/ppc_ksyms.c
index 9c98424277a8..65d14e6ddc3c 100644
--- a/arch/powerpc/kernel/ppc_ksyms.c
+++ b/arch/powerpc/kernel/ppc_ksyms.c
@@ -15,7 +15,6 @@
 #include <linux/bitops.h>
 
 #include <asm/page.h>
-#include <asm/semaphore.h>
 #include <asm/processor.h>
 #include <asm/cacheflush.h>
 #include <asm/uaccess.h>
diff --git a/arch/powerpc/kernel/semaphore.c b/arch/powerpc/kernel/semaphore.c
deleted file mode 100644
index 2f8c3c951394..000000000000
--- a/arch/powerpc/kernel/semaphore.c
+++ /dev/null
@@ -1,135 +0,0 @@
-/*
- * PowerPC-specific semaphore code.
- *
- * Copyright (C) 1999 Cort Dougan <cort@cs.nmt.edu>
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version
- * 2 of the License, or (at your option) any later version.
- *
- * April 2001 - Reworked by Paul Mackerras <paulus@samba.org>
- * to eliminate the SMP races in the old version between the updates
- * of `count' and `waking'.  Now we use negative `count' values to
- * indicate that some process(es) are waiting for the semaphore.
- */
-
-#include <linux/sched.h>
-#include <linux/init.h>
-#include <linux/module.h>
-
-#include <asm/atomic.h>
-#include <asm/semaphore.h>
-#include <asm/errno.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"
-"1:     lwarx   %0,0,%3\n"
-"       srawi   %1,%0,31\n"
-"       andc    %1,%0,%1\n"
-"       add     %1,%1,%4\n"
-        PPC405_ERR77(0,%3)
-"       stwcx.  %1,0,%3\n"
-"       bne     1b"
-        : "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
-        : "r" (&sem->count), "r" (incr), "m" (sem->count)
-        : "cc");
-
-        return old_count;
-}
-
-void __up(struct semaphore *sem)
-{
-        /*
-         * Note that we incremented count in up() before we came here,
-         * but that was ineffective since the result was <= 0, and
-         * any negative value of count is equivalent to 0.
-         * This ends up setting count to 1, unless count is now > 0
-         * (i.e. because some other cpu has called up() in the meantime),
-         * in which case we just increment count.
-         */
-        __sem_update_count(sem, 1);
-        wake_up(&sem->wait);
-}
-EXPORT_SYMBOL(__up);
-
-/*
- * Note that when we come in to __down or __down_interruptible,
- * we have already decremented count, but that decrement was
- * ineffective since the result was < 0, and any negative value
- * of count is equivalent to 0.
- * Thus it is only when we decrement count from some value > 0
- * that we have actually got the semaphore.
- */
-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);
-
-        /*
-         * Try to get the semaphore.  If the count is > 0, then we've
-         * got the semaphore; we decrement count and exit the loop.
-         * If the count is 0 or negative, we set it to -1, indicating
-         * that we are asleep, and then sleep.
-         */
-        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);
-
-        /*
-         * If there are any more sleepers, wake one of them up so
-         * that it can either get the semaphore, or set count to -1
-         * indicating that there are still processes sleeping.
-         */
-        wake_up(&sem->wait);
-}
-EXPORT_SYMBOL(__down);
-
-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)) {
-                        /*
-                         * A signal is pending - give up trying.
-                         * Set sem->count to 0 if it is negative,
-                         * since we are no longer sleeping.
-                         */
-                        __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;
-}
-EXPORT_SYMBOL(__down_interruptible);