On Wed, Sep 06, 2023 at 11:09:41AM -0700, Stephen Boyd wrote:
> It's possible for the polling loop in busy_loop() to get scheduled away
> for a long time.
>
> status = ipc_read_status(scu); // status = IPC_STATUS_BUSY
> <long time scheduled away>
> if (!(status & IPC_STATUS_BUSY))
>
> If this happens, then the status bit could change while the task is
> scheduled away and this function would never read the status again after
> timing out. Instead, the function will return -ETIMEDOUT when it's
> possible that scheduling didn't work out and the status bit was cleared.
> Bit polling code should always check the bit being polled one more time
> after the timeout in case this happens.
>
> Fix this by reading the status once more after the while loop breaks.
...
> static inline int busy_loop(struct intel_scu_ipc_dev *scu)
> {
> unsigned long end = jiffies + IPC_TIMEOUT;
> + u32 status;
>
> do {
> - u32 status;
> -
> status = ipc_read_status(scu);
> if (!(status & IPC_STATUS_BUSY))
> - return (status & IPC_STATUS_ERR) ? -EIO : 0;
> + goto not_busy;
Wouldn't simple 'break' suffice here?
> usleep_range(50, 100);
> } while (time_before(jiffies, end));
>
> - return -ETIMEDOUT;
> + status = ipc_read_status(scu);
> + if (status & IPC_STATUS_BUSY)
> + return -ETIMEDOUT;
> +not_busy:
> + return (status & IPC_STATUS_ERR) ? -EIO : 0;
> }
--
With Best Regards,
Andy Shevchenko
