Re: [PATCH V10 3/9] PCI: Create PCI library functions in support of DOE mailboxes.

[Ira Weiny]

On Mon, Jun 20, 2022 at 01:39:45AM -0700, Zhuo, Qiuxu wrote:
> > From: ira.weiny@xxxxxxxxx <ira.weiny@xxxxxxxxx>
> > Sent: Sunday, June 5, 2022 8:51 AM
> > ...
> > +static void retire_cur_task(struct pci_doe_mb *doe_mb) {
> > +	spin_lock(&doe_mb->task_lock);
> > +	doe_mb->cur_task = NULL;
> > +	spin_unlock(&doe_mb->task_lock);
> > +	wake_up_interruptible(&doe_mb->wq);
> > +}
> > +
> > +static void doe_statemachine_work(struct work_struct *work) {
> > +	struct delayed_work *w = to_delayed_work(work);
> > +	struct pci_doe_mb *doe_mb = container_of(w, struct pci_doe_mb,
> > +						 statemachine);
> > +	struct pci_dev *pdev = doe_mb->pdev;
> > +	int offset = doe_mb->cap_offset;
> > +	enum pci_doe_state prev_state;
> > +	struct pci_doe_task *task;
> > +	u32 val;
> > +	int rc;
> > +
> > +	spin_lock(&doe_mb->task_lock);
> > +	task = doe_mb->cur_task;
> > +	spin_unlock(&doe_mb->task_lock);
> 
>               I don't think it needs the lock protection here. 
>               No matter "task" is !NULL or NULL, it is checked before it's used within this function.

No it does not.

However, Dan has suggested reworking the workqueue and I think it will
eliminate this.  I kept the lock more as a marker of where cur_task was being
used even though it was not required.  The fact that the rest of the function
goes on to use a local alias was suspicious but was covered by the workqueue
operation.  I tried to explain that in the commit message but reworking as Dan
has suggested is better overall.

Thanks for the review!

Ira