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>
diff --git a/arch/sparc64/kernel/Makefile b/arch/sparc64/kernel/Makefile
index 1bf5b18..459462e 100644
--- a/arch/sparc64/kernel/Makefile
+++ b/arch/sparc64/kernel/Makefile
@@ -10,7 +10,7 @@
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 9974a68..0000000
--- 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 51fa773..051b8d9 100644
--- a/arch/sparc64/kernel/sparc64_ksyms.c
+++ b/arch/sparc64/kernel/sparc64_ksyms.c
@@ -130,12 +130,6 @@
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);