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powerpc/spufs: Explain conditional decrement of aff_sched_count 

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>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
This commit is contained in:
Andre Detsch 2008-10-21 11:16:09 +11:00 committed by Jeremy Kerr
parent 10baa26c8c
commit 34318c253b
1 changed files with 5 additions and 0 deletions
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arch/powerpc/platforms/cell/spufs/sched.c
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@ -444,6 +444,11 @@ static void spu_unbind_context(struct spu *spu, struct spu_context *ctx)
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);