[PATCH linux dev-4.10] drivers/hwmon/occ: Switch to non-blocking for occ reads

[Jeremy Kerr]

Hi Eddie,

> It's possible for the sbefifo ops to hang entirely if the system goes
> down (checkstop, etc), meaning that the occ and occ-hwmon drivers may
> hang during remove().

How does this address that though? Your comment implies that a thread is
stuck in occ_drv_read, is that correct?

I see that you're now opening in non-blocking mode, but:

> -	rc = occ_drv_read(client, (char *)resp, sizeof(*resp));
> -	if (rc < 0)
> -		goto err;
> +	do {
> +		rc = occ_drv_read(client, (char *)resp, sizeof(*resp));
> +		if (rc != -EAGAIN)
> +			break;
> +
> +		set_current_state(TASK_INTERRUPTIBLE);
> +		schedule_timeout(msecs_to_jiffies(OCC_CMD_INCOMPLETE_MS));
> +	} while (!p9_sbe_occ->cancel);

- the only way that you hit the !p9_sbe_occ->cancel condition is if
we've run the ->remove callback, in which case we *definitely* shouldn't
have threads still referencing the device. There seems to be nothing
preventing p9_sbe_occ from being free()ed underneath you.

If this patch works, it suggests that there's either a
reference-counting issue, or a memory leak.

Regards,


Jeremy