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[PATCH] spufs: fix locking in spu_acquire_runnable

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We need to check for validity of owner under down_write,
down_read is not enough.

Noticed by Al Viro.

Signed-off-by: Arnd Bergmann <arndb@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Arnd Bergmann 2006-01-04 20:31:21 +01:00 committed by Paul Mackerras
parent c902be71dc
commit 762cf6dac2
1 changed files with 6 additions and 4 deletions
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10
arch/powerpc/platforms/cell/spufs/context.c
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@ -120,27 +120,29 @@ int spu_acquire_runnable(struct spu_context *ctx)
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;
goto out;
}
up_read(&ctx->state_sema);
down_write(&ctx->state_sema);
if (ctx->state == SPU_STATE_SAVED) {
ret = spu_activate(ctx, 0);
ctx->state = SPU_STATE_RUNNABLE;
}
downgrade_write(&ctx->state_sema);
if (ret)
goto out;
downgrade_write(&ctx->state_sema);
/* On success, we return holding the lock */
return ret;
out:
/* Release here, to simplify calling code. */
up_read(&ctx->state_sema);
up_write(&ctx->state_sema);
return ret;
}