linux-kernel - Re: [PATCH V11 3/8] PCI: Create PCI library functions in support of DOE mailboxes.

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Date:   Tue, 14 Jun 2022 21:18:34 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     "Li, Ming" <ming4.li@...el.com>
CC:     Dan Williams <dan.j.williams@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        "Alison Schofield" <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        <linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
        <linux-pci@...r.kernel.org>
Subject: Re: [PATCH V11 3/8] PCI: Create PCI library functions in support of
 DOE mailboxes.

On Tue, Jun 14, 2022 at 11:53:29AM +0800, Li, Ming wrote:
> 
> 
> On 6/11/2022 4:22 AM, ira.weiny@...el.com wrote:
> > From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> > 

[snip]

> > +
> > +/**
> > + * pci_doe_submit_task() - Submit a task to be processed by the state machine
> > + *
> > + * @doe_mb: DOE mailbox capability to submit to
> > + * @task: task to be queued
> > + *
> > + * Submit a DOE task (request/response) to the DOE mailbox to be processed.
> > + * Returns upon queueing the task object.  If the queue is full this function
> > + * will sleep until there is room in the queue.
> > + *
> > + * task->complete will be called when the state machine is done processing this
> > + * task.
> > + *
> > + * Excess data will be discarded.
> > + *
> > + * RETURNS: 0 when task has been successful queued, -ERRNO on error
> > + */
> > +int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> > +{
> > +	if (!pci_doe_supports_prot(doe_mb, task->prot.vid, task->prot.type))
> > +		return -EINVAL;
> > +
> > +	/* DOE requests must be a whole number of DW */
> > +	if (task->request_pl_sz % sizeof(u32))
> > +		return -EINVAL;
> > +
> > +again:
> > +	spin_lock(&doe_mb->task_lock);
> > +	if (doe_mb->cur_task) {
> > +		spin_unlock(&doe_mb->task_lock);
> > +		wait_event_interruptible(doe_mb->wq, doe_mb->cur_task == NULL);
> Hi,
> do we need to check the returned value of wait_event_interruptible() here? if the returned value is -ERESTARTSYS, I think we should not try it again, just return.
> 

I'm not 100% sure it is necessary.  However, I don't think there is a point in
trying to continue if a system thread is interrupted.  So yea I think this is
a good idea.

Ira