Re: [PATCH v3 03/17] powerpc: Add PFO support to the VIO bus

From: Benjamin Herrenschmidt
Date: Mon Apr 30 2012 - 23:09:21 EST


Hrm... I don't like that much:

> + if (op->timeout)
> + deadline = jiffies + msecs_to_jiffies(op->timeout);
> +
> + while (true) {
> + hret = plpar_hcall_norets(H_COP, op->flags,
> + vdev->resource_id,
> + op->in, op->inlen, op->out,
> + op->outlen, op->csbcpb);
> +
> + if (hret == H_SUCCESS ||
> + (hret != H_NOT_ENOUGH_RESOURCES &&
> + hret != H_BUSY && hret != H_RESOURCE) ||
> + (op->timeout && time_after(deadline, jiffies)))
> + break;
> +
> + dev_dbg(dev, "%s: hcall ret(%ld), retrying.\n", __func__, hret);
> + }
> +

Is this meant to be called in atomic context ? If not, maybe it should
at the very least do a cond_resched() ?

Else, what about ceding the processor ? Or at the very least reducing
the thread priority for a bit ?

Shouldn't we also enforce to always have a timeout ? IE. Something like
30s or so if nothing specified to avoid having the kernel just hard
lock...

In general I don't like that sort of synchronous code, I'd rather return
the busy status up the chain which gives a chance to the caller to take
more appropriate measures depending on what it's doing, but that really
depends what you use that synchronous call for. I suppose if it's for
configuration type operations, it's ok...

Cheers,
Ben.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/