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powerpc/spufs: explain conditional decrement of aff_sched_count

Message ID 200810201327.07179.adetsch@br.ibm.com
State Accepted
Headers show

Commit Message

Andre Detsch Oct. 20, 2008, 3:27 p.m. UTC 
This patch adds a comment to clarify why atomic_dec_if_positive is being used
to decrement gang's aff_sched_count on SPU context unbind.

Signed-off-by: Andre Detsch <adetsch@br.ibm.com>
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Patch

Index: spufs/arch/powerpc/platforms/cell/spufs/sched.c
===================================================================
--- spufs.orig/arch/powerpc/platforms/cell/spufs/sched.c
+++ spufs/arch/powerpc/platforms/cell/spufs/sched.c
@@ -437,6 +437,11 @@  static void spu_unbind_context(struct sp
 		atomic_dec(&cbe_spu_info[spu->node].reserved_spus);

 	if (ctx->gang)
+		/*
+		 * If ctx->gang->aff_sched_count is positive, SPU affinity is
+		 * being considered in this gang. Using atomic_dec_if_positive
+		 * allow us to skip an explicit check for affinity in this gang
+		 */
 		atomic_dec_if_positive(&ctx->gang->aff_sched_count);

 	spu_switch_notify(spu, NULL);