linux-kernel - Re: [PATCH v16 07/34] gunyah: rsc_mgr: Add resource manager RPC core

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Date: Wed, 10 Jan 2024 19:41:01 +0800
From: Hillf Danton <hdanton@...a.com>
To: Elliot Berman <quic_eberman@...cinc.com>
Cc: Will Deacon <will@...nel.org>,
	Sean Christopherson <seanjc@...gle.com>,
	linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v16 07/34] gunyah: rsc_mgr: Add resource manager RPC core

On Tue, 9 Jan 2024 11:37:45 -0800 Elliot Berman <quic_eberman@...cinc.com>
> +
> +static irqreturn_t gunyah_rm_tx(int irq, void *data)
> +{
> +	struct gunyah_rm *rm = data;
> +
> +	complete_all(&rm->send_ready);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int gunyah_rm_msgq_send(struct gunyah_rm *rm, size_t size, bool push)
> +	__must_hold(&rm->send_lock)
> +{
> +	const u64 tx_flags = push ? GUNYAH_HYPERCALL_MSGQ_TX_FLAGS_PUSH : 0;
> +	enum gunyah_error gunyah_error;
> +	void *data = &rm->send_msg[0];
> +	bool ready;

	lockdep_assert_held(&rm->send_lock); instead of __must_hold
> +
> +again:
> +	wait_for_completion(&rm->send_ready);
> +	/* reinit completion before hypercall. As soon as hypercall returns, we could get the
> +	 * ready interrupt. This might be before we have time to reinit the completion
> +	 */
> +	reinit_completion(&rm->send_ready);

Given wait_for_completion(&rm->send_ready) with rm->send_lock held,
complete(&rm->send_ready) works for you with the bonus of cutting this
reinit off.

> +	gunyah_error = gunyah_hypercall_msgq_send(rm->tx_ghrsc.capid, size,
> +						  data, tx_flags, &ready);
> +
> +	/* Should never happen because Linux properly tracks the ready-state of the msgq */
> +	if (WARN_ON(gunyah_error == GUNYAH_ERROR_MSGQUEUE_FULL))
> +		goto again;
> +
> +	if (ready)
> +		complete_all(&rm->send_ready);
> +
> +	return gunyah_error_remap(gunyah_error);
> +}