Re: [PATCH v5 5/9] IB/isert: Replace semaphore sem with completion

From: Sagi Grimberg
Date: Mon Nov 21 2016 - 07:33:13 EST



diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c
index 6dd43f6..de80f56 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.c
+++ b/drivers/infiniband/ulp/isert/ib_isert.c
@@ -619,7 +619,7 @@
mutex_unlock(&isert_np->mutex);

isert_info("np %p: Allow accept_np to continue\n", isert_np);
- up(&isert_np->sem);
+ complete(&isert_np->comp);
}

static void
@@ -2311,7 +2311,7 @@ struct rdma_cm_id *
isert_err("Unable to allocate struct isert_np\n");
return -ENOMEM;
}
- sema_init(&isert_np->sem, 0);
+ init_completion(&isert_np->comp);

This is still racy, a connect event can complete just before we
init the completion and *will* get lost...

This code started off with a waitqueue which exposes the same
problem, see:
531b7bf4bd79 Target/iser: Fix iscsit_accept_np and rdma_cm racy flow

So, still NAK from me...

I don't see what you mean here. The code using a waitqueue had no
counter but the completion does.

The problem here is that init_completion sets the counter to zero
and between this thread wakes up and until it initializes comp->done
we might have another connect event completing it and I fail to
see how this is handled correctly.