[POWERPC] spufs: simplify state_mutex

The r/w semaphore to lock the spus was overkill and can be replaced
with a mutex to make it faster, simpler and easier to debug.  It also
helps to allow making most spufs interruptible in future patches.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>

3 files changed, 17 insertions, 30 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/context.c b/arch/powerpc/platforms/cell/spufs/context.c
index ccffc449763b..c9aab9b1cd8a 100644
--- a/arch/powerpc/platforms/cell/spufs/context.c
+++ b/arch/powerpc/platforms/cell/spufs/context.c
@@ -42,7 +42,7 @@ struct spu_context *alloc_spu_context(struct spu_gang *gang)
         }
         spin_lock_init(&ctx->mmio_lock);
         kref_init(&ctx->kref);
-        init_rwsem(&ctx->state_sema);
+        mutex_init(&ctx->state_mutex);
         init_MUTEX(&ctx->run_sema);
         init_waitqueue_head(&ctx->ibox_wq);
         init_waitqueue_head(&ctx->wbox_wq);
@@ -65,9 +65,9 @@ void destroy_spu_context(struct kref *kref)
 {
         struct spu_context *ctx;
         ctx = container_of(kref, struct spu_context, kref);
-        down_write(&ctx->state_sema);
+        mutex_lock(&ctx->state_mutex);
         spu_deactivate(ctx);
-        up_write(&ctx->state_sema);
+        mutex_unlock(&ctx->state_mutex);
         spu_fini_csa(&ctx->csa);
         if (ctx->gang)
                 spu_gang_remove_ctx(ctx->gang, ctx);
@@ -98,12 +98,12 @@ void spu_forget(struct spu_context *ctx)
 
 void spu_acquire(struct spu_context *ctx)
 {
-        down_read(&ctx->state_sema);
+        mutex_lock(&ctx->state_mutex);
 }
 
 void spu_release(struct spu_context *ctx)
 {
-        up_read(&ctx->state_sema);
+        mutex_unlock(&ctx->state_mutex);
 }
 
 void spu_unmap_mappings(struct spu_context *ctx)
@@ -128,7 +128,7 @@ int spu_acquire_exclusive(struct spu_context *ctx)
 {
         int ret = 0;
 
-        down_write(&ctx->state_sema);
+        mutex_lock(&ctx->state_mutex);
         /* ctx is about to be freed, can't acquire any more */
         if (!ctx->owner) {
                 ret = -EINVAL;
@@ -146,7 +146,7 @@ int spu_acquire_exclusive(struct spu_context *ctx)
 
 out:
         if (ret)
-                up_write(&ctx->state_sema);
+                mutex_unlock(&ctx->state_mutex);
         return ret;
 }
 
@@ -154,14 +154,12 @@ int spu_acquire_runnable(struct spu_context *ctx)
 {
         int ret = 0;
 
-        down_read(&ctx->state_sema);
+        mutex_lock(&ctx->state_mutex);
         if (ctx->state == SPU_STATE_RUNNABLE) {
                 ctx->spu->prio = current->prio;
                 return 0;
         }
-        up_read(&ctx->state_sema);
 
-        down_write(&ctx->state_sema);
         /* ctx is about to be freed, can't acquire any more */
         if (!ctx->owner) {
                 ret = -EINVAL;
@@ -174,29 +172,18 @@ int spu_acquire_runnable(struct spu_context *ctx)
                         goto out;
         }
 
-        downgrade_write(&ctx->state_sema);
         /* On success, we return holding the lock */
-
         return ret;
 out:
         /* Release here, to simplify calling code. */
-        up_write(&ctx->state_sema);
+        mutex_unlock(&ctx->state_mutex);
 
         return ret;
 }
 
 void spu_acquire_saved(struct spu_context *ctx)
 {
-        down_read(&ctx->state_sema);
-
-        if (ctx->state == SPU_STATE_SAVED)
-                return;
-
-        up_read(&ctx->state_sema);
-        down_write(&ctx->state_sema);
-
+        mutex_lock(&ctx->state_mutex);
         if (ctx->state == SPU_STATE_RUNNABLE)
                 spu_deactivate(ctx);
-
-        downgrade_write(&ctx->state_sema);
 }
diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index 1d330f67f5ae..c61a34b14083 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -233,11 +233,11 @@ static void spu_prio_wait(struct spu_context *ctx, u64 flags)
         spu_add_wq(wq, &wait, prio);
 
         if (!signal_pending(current)) {
-                up_write(&ctx->state_sema);
+                mutex_unlock(&ctx->state_mutex);
                 pr_debug("%s: pid=%d prio=%d\n", __FUNCTION__,
                          current->pid, current->prio);
                 schedule();
-                down_write(&ctx->state_sema);
+                mutex_lock(&ctx->state_mutex);
         }
 
         spu_del_wq(wq, &wait, prio);
@@ -334,7 +334,7 @@ void spu_yield(struct spu_context *ctx)
         struct spu *spu;
         int need_yield = 0;
 
-        if (down_write_trylock(&ctx->state_sema)) {
+        if (mutex_trylock(&ctx->state_mutex)) {
                 if ((spu = ctx->spu) != NULL) {
                         int best = sched_find_first_bit(spu_prio->bitmap);
                         if (best < MAX_PRIO) {
@@ -346,7 +346,7 @@ void spu_yield(struct spu_context *ctx)
                                 spu->prio = MAX_PRIO;
                         }
                 }
-                up_write(&ctx->state_sema);
+                mutex_unlock(&ctx->state_mutex);
         }
         if (unlikely(need_yield))
                 yield();
diff --git a/arch/powerpc/platforms/cell/spufs/spufs.h b/arch/powerpc/platforms/cell/spufs/spufs.h
index 9b44abe921cc..de2401afb226 100644
--- a/arch/powerpc/platforms/cell/spufs/spufs.h
+++ b/arch/powerpc/platforms/cell/spufs/spufs.h
@@ -23,7 +23,7 @@
 #define SPUFS_H
 
 #include <linux/kref.h>
-#include <linux/rwsem.h>
+#include <linux/mutex.h>
 #include <linux/spinlock.h>
 #include <linux/fs.h>
 
@@ -53,7 +53,7 @@ struct spu_context {
         u64 object_id;             /* user space pointer for oprofile */
 
         enum { SPU_STATE_RUNNABLE, SPU_STATE_SAVED } state;
-        struct rw_semaphore state_sema;
+        struct mutex state_mutex;
         struct semaphore run_sema;
 
         struct mm_struct *owner;
@@ -173,7 +173,7 @@ int spu_acquire_exclusive(struct spu_context *ctx);
 
 static inline void spu_release_exclusive(struct spu_context *ctx)
 {
-        up_write(&ctx->state_sema);
+        mutex_unlock(&ctx->state_mutex);
 }
 
 int spu_activate(struct spu_context *ctx, u64 flags);