Re: [PATCH V2 1/2] PCI/DOE: Remove the pci_doe_flush_mb() call

Jonathan Cameron
2022-11-22T16:34:38Z

On Tue, 22 Nov 2022 07:53:23 -0800
ira.weiny@intel.com wrote:

> From: Ira Weiny <ira.weiny@intel.com>
>
> 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.
>
> For these reasons, pci_doe_flush_mb() will never be called while tasks
> are being processed and there is no use for it.
>
> Remove the dead code around pci_doe_flush_mb().
>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>

Looks fine I think, though one question inline.

> ---
> drivers/pci/doe.c | 48 ++++-------------------------------------------
> 1 file changed, 4 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
> index e402f05068a5..260313e9052e 100644
> --- a/drivers/pci/doe.c
> +++ b/drivers/pci/doe.c
> @@ -24,10 +24,9 @@
>
> /* 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)
> +#define PCI_DOE_POLL_INTERVAL 8

Why this change?

>
> -#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 +52,6 @@ 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 +72,9 @@ 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);
> pci_read_config_dword(pdev, offset + PCI_DOE_STATUS, &val);
>
> /* Abort success! */
> @@ -278,11 +265,7 @@ 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);
> goto retry_resp;
> }
>
> @@ -383,21 +366,6 @@ 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 +418,6 @@ 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",