[POWERPC] spufs: rework class 0 and 1 interrupt handling

Based on original patches from
 Arnd Bergmann <arnd.bergman@de.ibm.com>; and
 Luke Browning <lukebr@linux.vnet.ibm.com>

Currently, spu contexts need to be loaded to the SPU in order to take
class 0 and class 1 exceptions.

This change makes the actual interrupt-handlers much simpler (ie,
set the exception information in the context save area), and defers the
handling code to the spufs_handle_class[01] functions, called from
spufs_run_spu.

This should improve the concurrency of the spu scheduling leading to
greater SPU utilization when SPUs are overcommited.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 34 insertions, 16 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/run.c b/arch/powerpc/platforms/cell/spufs/run.c
index b3cc1dd72185..3b3de6c7ee5b 100644
--- a/arch/powerpc/platforms/cell/spufs/run.c
+++ b/arch/powerpc/platforms/cell/spufs/run.c
@@ -15,7 +15,30 @@ void spufs_stop_callback(struct spu *spu)
 {
         struct spu_context *ctx = spu->ctx;
 
-        wake_up_all(&ctx->stop_wq);
+        /*
+         * It should be impossible to preempt a context while an exception
+         * is being processed, since the context switch code is specially
+         * coded to deal with interrupts ... But, just in case, sanity check
+         * the context pointer.  It is OK to return doing nothing since
+         * the exception will be regenerated when the context is resumed.
+         */
+        if (ctx) {
+                /* Copy exception arguments into module specific structure */
+                ctx->csa.class_0_pending = spu->class_0_pending;
+                ctx->csa.dsisr = spu->dsisr;
+                ctx->csa.dar = spu->dar;
+
+                /* ensure that the exception status has hit memory before a
+                 * thread waiting on the context's stop queue is woken */
+                smp_wmb();
+
+                wake_up_all(&ctx->stop_wq);
+        }
+
+        /* Clear callback arguments from spu structure */
+        spu->class_0_pending = 0;
+        spu->dsisr = 0;
+        spu->dar = 0;
 }
 
 static inline int spu_stopped(struct spu_context *ctx, u32 *stat)
@@ -29,9 +52,9 @@ static inline int spu_stopped(struct spu_context *ctx, u32 *stat)
         if (ctx->state != SPU_STATE_RUNNABLE ||
             test_bit(SPU_SCHED_NOTIFY_ACTIVE, &ctx->sched_flags))
                 return 1;
-        pte_fault = spu->dsisr &
+        pte_fault = ctx->csa.dsisr &
             (MFC_DSISR_PTE_NOT_FOUND | MFC_DSISR_ACCESS_DENIED);
-        return (!(*stat & SPU_STATUS_RUNNING) || pte_fault || spu->class_0_pending) ?
+        return (!(*stat & SPU_STATUS_RUNNING) || pte_fault || ctx->csa.class_0_pending) ?
                 1 : 0;
 }
 
@@ -287,18 +310,6 @@ static int spu_process_callback(struct spu_context *ctx)
         return ret;
 }
 
-static inline int spu_process_events(struct spu_context *ctx)
-{
-        struct spu *spu = ctx->spu;
-        int ret = 0;
-
-        if (spu->class_0_pending)
-                ret = spu_irq_class_0_bottom(spu);
-        if (!ret && signal_pending(current))
-                ret = -ERESTARTSYS;
-        return ret;
-}
-
 long spufs_run_spu(struct spu_context *ctx, u32 *npc, u32 *event)
 {
         int ret;
@@ -364,13 +375,20 @@ long spufs_run_spu(struct spu_context *ctx, u32 *npc, u32 *event)
                 if (ret)
                         break;
 
+                ret = spufs_handle_class0(ctx);
+                if (ret)
+                        break;
+
                 if (unlikely(ctx->state != SPU_STATE_RUNNABLE)) {
                         ret = spu_reacquire_runnable(ctx, npc, &status);
                         if (ret)
                                 goto out2;
                         continue;
                 }
-                ret = spu_process_events(ctx);
+
+                if (signal_pending(current))
+                        ret = -ERESTARTSYS;
+
 
         } while (!ret && !(status & (SPU_STATUS_STOPPED_BY_STOP |
                                       SPU_STATUS_STOPPED_BY_HALT |