On Sun, Nov 27, 2022 at 08:03:37PM -0800, Ira Weiny wrote:
> From: Ira Weiny <ira.weiny@xxxxxxxxx>
>
> pci_doe_flush_mb() does not work and is currently unused.
>
> It does not work because each struct doe_mb is managed as part of the
> PCI device. They can't go away as long as the PCI device exists.
> pci_doe_flush_mb() was set up to flush the workqueue and prevent any
> further submissions to the mailboxes when the PCI device goes away.
> Unfortunately, this was fundamentally flawed. There was no guarantee
> that a struct doe_mb remained after pci_doe_flush_mb() returned.
> Therefore, the doe_mb state could be invalid when those threads waiting
> on the workqueue were flushed.
>
> Fortunately the current code is safe because all callers make a
> synchronous call to pci_doe_submit_task() and maintain a reference on
> the PCI device. Therefore pci_doe_flush_mb() is effectively unused.
>
> Rather than attempt to fix pci_doe_flush_mb() just remove the dead code
> around pci_doe_flush_mb().
The commit message says "Remove ...." and the commit log only
talks about removing code, yet an msleep() is added.
Can those be clearer?
>
> Cc: Lukas Wunner <lukas@xxxxxxxxx>
> Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
>
> ---
> Changes from V2:
> Lukas
> Clarify commit message.
> Jonathan
> Add comment for changed poll interval.
> ---
> drivers/pci/doe.c | 49 +++++------------------------------------------
> 1 file changed, 5 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
> index e402f05068a5..685e7d26c7eb 100644
> --- a/drivers/pci/doe.c
> +++ b/drivers/pci/doe.c
> @@ -24,10 +24,10 @@
>
> /* Timeout of 1 second from 6.30.2 Operation, PCI Spec r6.0 */
> #define PCI_DOE_TIMEOUT HZ
> -#define PCI_DOE_POLL_INTERVAL (PCI_DOE_TIMEOUT / 128)
> +/* Interval to poll mailbox status */
> +#define PCI_DOE_POLL_INTERVAL_MSECS 8
>
> -#define PCI_DOE_FLAG_CANCEL 0
> -#define PCI_DOE_FLAG_DEAD 1
> +#define PCI_DOE_FLAG_DEAD 0
>
> /**
> * struct pci_doe_mb - State for a single DOE mailbox
> @@ -53,15 +53,6 @@ struct pci_doe_mb {
> unsigned long flags;
> };
>
> -static int pci_doe_wait(struct pci_doe_mb *doe_mb, unsigned long timeout)
> -{
> - if (wait_event_timeout(doe_mb->wq,
> - test_bit(PCI_DOE_FLAG_CANCEL, &doe_mb->flags),
> - timeout))
> - return -EIO;
> - return 0;
> -}
> -
> static void pci_doe_write_ctrl(struct pci_doe_mb *doe_mb, u32 val)
> {
> struct pci_dev *pdev = doe_mb->pdev;
> @@ -82,12 +73,9 @@ static int pci_doe_abort(struct pci_doe_mb *doe_mb)
> pci_doe_write_ctrl(doe_mb, PCI_DOE_CTRL_ABORT);
>
> do {
> - int rc;
> u32 val;
>
> - rc = pci_doe_wait(doe_mb, PCI_DOE_POLL_INTERVAL);
> - if (rc)
> - return rc;
> + msleep_interruptible(PCI_DOE_POLL_INTERVAL_MSECS);
> pci_read_config_dword(pdev, offset + PCI_DOE_STATUS, &val);
>
> /* Abort success! */
> @@ -278,11 +266,7 @@ static void doe_statemachine_work(struct work_struct *work)
> signal_task_abort(task, -EIO);
> return;
> }
> - rc = pci_doe_wait(doe_mb, PCI_DOE_POLL_INTERVAL);
> - if (rc) {
> - signal_task_abort(task, rc);
> - return;
> - }
> + msleep_interruptible(PCI_DOE_POLL_INTERVAL_MSECS);
> goto retry_resp;
> }
>
> @@ -383,21 +367,6 @@ static void pci_doe_destroy_workqueue(void *mb)
> destroy_workqueue(doe_mb->work_queue);
> }
>
> -static void pci_doe_flush_mb(void *mb)
> -{
> - struct pci_doe_mb *doe_mb = mb;
> -
> - /* Stop all pending work items from starting */
> - set_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags);
> -
> - /* Cancel an in progress work item, if necessary */
> - set_bit(PCI_DOE_FLAG_CANCEL, &doe_mb->flags);
> - wake_up(&doe_mb->wq);
> -
> - /* Flush all work items */
> - flush_workqueue(doe_mb->work_queue);
> -}
> -
> /**
> * pcim_doe_create_mb() - Create a DOE mailbox object
> *
> @@ -450,14 +419,6 @@ struct pci_doe_mb *pcim_doe_create_mb(struct pci_dev *pdev, u16 cap_offset)
> return ERR_PTR(rc);
> }
>
> - /*
> - * The state machine and the mailbox should be in sync now;
> - * Set up mailbox flush prior to using the mailbox to query protocols.
> - */
> - rc = devm_add_action_or_reset(dev, pci_doe_flush_mb, doe_mb);
> - if (rc)
> - return ERR_PTR(rc);
> -
> rc = pci_doe_cache_protocols(doe_mb);
> if (rc) {
> pci_err(pdev, "[%x] failed to cache protocols : %d\n",
> --
> 2.37.2
>
