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Date: Mon, 28 Nov 2022 11:47:37 -0800
From: Ira Weiny <ira.weiny@...el.com>
To: Alison Schofield <alison.schofield@...el.com>
CC: Dan Williams <dan.j.williams@...el.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Gregory Price <gregory.price@...verge.com>,
"Jonathan Cameron" <Jonathan.Cameron@...wei.com>,
"Li, Ming" <ming4.li@...el.com>, Lukas Wunner <lukas@...ner.de>,
Vishal Verma <vishal.l.verma@...el.com>,
<linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-cxl@...r.kernel.org>
Subject: Re: [PATCH V3 2/2] PCI/DOE: Remove asynchronous task support
On Mon, Nov 28, 2022 at 09:58:11AM -0800, Alison Schofield wrote:
> On Sun, Nov 27, 2022 at 08:03:38PM -0800, Ira Weiny wrote:
> > From: Ira Weiny <ira.weiny@...el.com>
> >
> > Gregory Price and Jonathan Cameron reported a bug within
> > pci_doe_submit_task().[1] The issue was that work item initialization
> > needs to be done with either INIT_WORK_ONSTACK() or INIT_WORK()
> > depending on how the work item is allocated.
> >
> > Initially, it was anticipated that DOE tasks were going to need to be
> > submitted asynchronously and the code was designed thusly. Many
> > alternatives were discussed to fix the work initialization issue.[2]
> >
> > However, all current users submit tasks synchronously and this has
> > therefore become an unneeded maintenance burden. Remove the extra
> > maintenance burden by replacing asynchronous task submission with
> > a synchronous wait function.[3]
>
> Commit msg: Please look at replacing this:
> PCI/DOE: Remove asynchronous task support
> with something like this:
> PCI/DOE: Replace async task submission with sync wait function
Ok yes this makes sense.
Thanks for looking!
Ira
> to more accurately reflect what this patch does. It is not
> only removing code.
>
> Like the first patch, I'm unfamiliar w the details, and am
> just expecting that a patch that says 'Remove' doesn't add
> anything.
>
> >
> > [1] https://lore.kernel.org/linux-cxl/20221014151045.24781-1-Jonathan.Cameron@huawei.com/T/#m88a7f50dcce52f30c8bf5c3dcc06fa9843b54a2d
> > [2] https://lore.kernel.org/linux-cxl/Y3kSDQDur+IUDs2O@iweiny-mobl/T/#m0f057773d9c75432fcfcc54a2604483fe82abe92
> > [3] https://lore.kernel.org/linux-cxl/Y3kSDQDur+IUDs2O@iweiny-mobl/T/#m32d3f9b208ef7486bc148d94a326b26b2d3e69ff
> >
> > Reported-by: Gregory Price <gregory.price@...verge.com>
> > Reported-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> > Suggested-by: Dan Williams <dan.j.williams@...el.com>
> > Suggested-by: "Li, Ming" <ming4.li@...el.com>
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> >
> > ---
> > Changes from V2:
> > Jonathan
> > Fix comment on struct pci_doe_mb
> > Remove signal_task_complete()
> >
> > Changes from V1:
> > Dan Williams:
> > Use mutex_lock_interruptible()
> > Adjust comment to lock the doe_mb structure not the
> > code
> > Adjust the locking based on the new series which eliminated
> > PCI_DOE_FLAG_CANCEL.
> >
> > Thanks to Dan for the bulk of the patch.
> > Thanks to Ming for pointing out the need for a lock to prevent more
> > than 1 task from being processed at a time.
> > ---
> > drivers/cxl/core/pci.c | 16 ++------
> > drivers/pci/doe.c | 86 +++++++++++++----------------------------
> > include/linux/pci-doe.h | 11 +-----
> > 3 files changed, 31 insertions(+), 82 deletions(-)
> >
> > diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> > index 9240df53ed87..58977e0712b6 100644
> > --- a/drivers/cxl/core/pci.c
> > +++ b/drivers/cxl/core/pci.c
> > @@ -490,21 +490,14 @@ static struct pci_doe_mb *find_cdat_doe(struct device *uport)
> > CXL_DOE_TABLE_ACCESS_TABLE_TYPE_CDATA) | \
> > FIELD_PREP(CXL_DOE_TABLE_ACCESS_ENTRY_HANDLE, (entry_handle)))
> >
> > -static void cxl_doe_task_complete(struct pci_doe_task *task)
> > -{
> > - complete(task->private);
> > -}
> > -
> > struct cdat_doe_task {
> > u32 request_pl;
> > u32 response_pl[32];
> > - struct completion c;
> > struct pci_doe_task task;
> > };
> >
> > #define DECLARE_CDAT_DOE_TASK(req, cdt) \
> > struct cdat_doe_task cdt = { \
> > - .c = COMPLETION_INITIALIZER_ONSTACK(cdt.c), \
> > .request_pl = req, \
> > .task = { \
> > .prot.vid = PCI_DVSEC_VENDOR_ID_CXL, \
> > @@ -513,8 +506,6 @@ struct cdat_doe_task cdt = { \
> > .request_pl_sz = sizeof(cdt.request_pl), \
> > .response_pl = cdt.response_pl, \
> > .response_pl_sz = sizeof(cdt.response_pl), \
> > - .complete = cxl_doe_task_complete, \
> > - .private = &cdt.c, \
> > } \
> > }
> >
> > @@ -525,12 +516,12 @@ static int cxl_cdat_get_length(struct device *dev,
> > DECLARE_CDAT_DOE_TASK(CDAT_DOE_REQ(0), t);
> > int rc;
> >
> > - rc = pci_doe_submit_task(cdat_doe, &t.task);
> > + rc = pci_doe_submit_task_wait(cdat_doe, &t.task);
> > if (rc < 0) {
> > dev_err(dev, "DOE submit failed: %d", rc);
> > return rc;
> > }
> > - wait_for_completion(&t.c);
> > +
> > if (t.task.rv < sizeof(u32))
> > return -EIO;
> >
> > @@ -554,12 +545,11 @@ static int cxl_cdat_read_table(struct device *dev,
> > u32 *entry;
> > int rc;
> >
> > - rc = pci_doe_submit_task(cdat_doe, &t.task);
> > + rc = pci_doe_submit_task_wait(cdat_doe, &t.task);
> > if (rc < 0) {
> > dev_err(dev, "DOE submit failed: %d", rc);
> > return rc;
> > }
> > - wait_for_completion(&t.c);
> > /* 1 DW header + 1 DW data min */
> > if (t.task.rv < (2 * sizeof(u32)))
> > return -EIO;
> > diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
> > index 685e7d26c7eb..b399f0f4fb5d 100644
> > --- a/drivers/pci/doe.c
> > +++ b/drivers/pci/doe.c
> > @@ -18,7 +18,6 @@
> > #include <linux/mutex.h>
> > #include <linux/pci.h>
> > #include <linux/pci-doe.h>
> > -#include <linux/workqueue.h>
> >
> > #define PCI_DOE_PROTOCOL_DISCOVERY 0
> >
> > @@ -40,7 +39,7 @@
> > * @cap_offset: Capability offset
> > * @prots: Array of protocols supported (encoded as long values)
> > * @wq: Wait queue for work item
> > - * @work_queue: Queue of pci_doe_work items
> > + * @lock: Lock state of doe_mb during task processing
> > * @flags: Bit array of PCI_DOE_FLAG_* flags
> > */
> > struct pci_doe_mb {
> > @@ -49,7 +48,7 @@ struct pci_doe_mb {
> > struct xarray prots;
> >
> > wait_queue_head_t wq;
> > - struct workqueue_struct *work_queue;
> > + struct mutex lock;
> > unsigned long flags;
> > };
> >
> > @@ -196,12 +195,6 @@ static int pci_doe_recv_resp(struct pci_doe_mb *doe_mb, struct pci_doe_task *tas
> > return min(length, task->response_pl_sz / sizeof(u32)) * sizeof(u32);
> > }
> >
> > -static void signal_task_complete(struct pci_doe_task *task, int rv)
> > -{
> > - task->rv = rv;
> > - task->complete(task);
> > -}
> > -
> > static void signal_task_abort(struct pci_doe_task *task, int rv)
> > {
> > struct pci_doe_mb *doe_mb = task->doe_mb;
> > @@ -216,13 +209,11 @@ static void signal_task_abort(struct pci_doe_task *task, int rv)
> > doe_mb->cap_offset);
> > set_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags);
> > }
> > - signal_task_complete(task, rv);
> > + task->rv = rv;
> > }
> >
> > -static void doe_statemachine_work(struct work_struct *work)
> > +static void exec_task(struct pci_doe_task *task)
> > {
> > - struct pci_doe_task *task = container_of(work, struct pci_doe_task,
> > - work);
> > struct pci_doe_mb *doe_mb = task->doe_mb;
> > struct pci_dev *pdev = doe_mb->pdev;
> > int offset = doe_mb->cap_offset;
> > @@ -231,7 +222,7 @@ static void doe_statemachine_work(struct work_struct *work)
> > int rc;
> >
> > if (test_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags)) {
> > - signal_task_complete(task, -EIO);
> > + task->rv = -EIO;
> > return;
> > }
> >
> > @@ -276,12 +267,7 @@ static void doe_statemachine_work(struct work_struct *work)
> > return;
> > }
> >
> > - signal_task_complete(task, rc);
> > -}
> > -
> > -static void pci_doe_task_complete(struct pci_doe_task *task)
> > -{
> > - complete(task->private);
> > + task->rv = rc;
> > }
> >
> > static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 *index, u16 *vid,
> > @@ -290,7 +276,6 @@ static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 *index, u16 *vid,
> > u32 request_pl = FIELD_PREP(PCI_DOE_DATA_OBJECT_DISC_REQ_3_INDEX,
> > *index);
> > u32 response_pl;
> > - DECLARE_COMPLETION_ONSTACK(c);
> > struct pci_doe_task task = {
> > .prot.vid = PCI_VENDOR_ID_PCI_SIG,
> > .prot.type = PCI_DOE_PROTOCOL_DISCOVERY,
> > @@ -298,17 +283,13 @@ static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 *index, u16 *vid,
> > .request_pl_sz = sizeof(request_pl),
> > .response_pl = &response_pl,
> > .response_pl_sz = sizeof(response_pl),
> > - .complete = pci_doe_task_complete,
> > - .private = &c,
> > };
> > int rc;
> >
> > - rc = pci_doe_submit_task(doe_mb, &task);
> > + rc = pci_doe_submit_task_wait(doe_mb, &task);
> > if (rc < 0)
> > return rc;
> >
> > - wait_for_completion(&c);
> > -
> > if (task.rv != sizeof(response_pl))
> > return -EIO;
> >
> > @@ -360,13 +341,6 @@ static void pci_doe_xa_destroy(void *mb)
> > xa_destroy(&doe_mb->prots);
> > }
> >
> > -static void pci_doe_destroy_workqueue(void *mb)
> > -{
> > - struct pci_doe_mb *doe_mb = mb;
> > -
> > - destroy_workqueue(doe_mb->work_queue);
> > -}
> > -
> > /**
> > * pcim_doe_create_mb() - Create a DOE mailbox object
> > *
> > @@ -392,25 +366,13 @@ struct pci_doe_mb *pcim_doe_create_mb(struct pci_dev *pdev, u16 cap_offset)
> > doe_mb->pdev = pdev;
> > doe_mb->cap_offset = cap_offset;
> > init_waitqueue_head(&doe_mb->wq);
> > + mutex_init(&doe_mb->lock);
> >
> > xa_init(&doe_mb->prots);
> > rc = devm_add_action(dev, pci_doe_xa_destroy, doe_mb);
> > if (rc)
> > return ERR_PTR(rc);
> >
> > - doe_mb->work_queue = alloc_ordered_workqueue("%s %s DOE [%x]", 0,
> > - dev_driver_string(&pdev->dev),
> > - pci_name(pdev),
> > - doe_mb->cap_offset);
> > - if (!doe_mb->work_queue) {
> > - pci_err(pdev, "[%x] failed to allocate work queue\n",
> > - doe_mb->cap_offset);
> > - return ERR_PTR(-ENOMEM);
> > - }
> > - rc = devm_add_action_or_reset(dev, pci_doe_destroy_workqueue, doe_mb);
> > - if (rc)
> > - return ERR_PTR(rc);
> > -
> > /* Reset the mailbox by issuing an abort */
> > rc = pci_doe_abort(doe_mb);
> > if (rc) {
> > @@ -457,24 +419,25 @@ bool pci_doe_supports_prot(struct pci_doe_mb *doe_mb, u16 vid, u8 type)
> > EXPORT_SYMBOL_GPL(pci_doe_supports_prot);
> >
> > /**
> > - * pci_doe_submit_task() - Submit a task to be processed by the state machine
> > + * pci_doe_submit_task_wait() - Submit and execute a task
> > *
> > * @doe_mb: DOE mailbox capability to submit to
> > - * @task: task to be queued
> > - *
> > - * Submit a DOE task (request/response) to the DOE mailbox to be processed.
> > - * Returns upon queueing the task object. If the queue is full this function
> > - * will sleep until there is room in the queue.
> > + * @task: task to be run
> > *
> > - * task->complete will be called when the state machine is done processing this
> > - * task.
> > + * Submit and run DOE task (request/response) to the DOE mailbox to be
> > + * processed.
> > *
> > * Excess data will be discarded.
> > *
> > - * RETURNS: 0 when task has been successfully queued, -ERRNO on error
> > + * Context: non-interrupt
> > + *
> > + * RETURNS: 0 when task was executed, the @task->rv holds the status
> > + * result of the executed opertion, -ERRNO on failure to submit.
> > */
> > -int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> > +int pci_doe_submit_task_wait(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> > {
> > + int rc;
> > +
> > if (!pci_doe_supports_prot(doe_mb, task->prot.vid, task->prot.type))
> > return -EINVAL;
> >
> > @@ -490,8 +453,13 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> > return -EIO;
> >
> > task->doe_mb = doe_mb;
> > - INIT_WORK(&task->work, doe_statemachine_work);
> > - queue_work(doe_mb->work_queue, &task->work);
> > +
> > + rc = mutex_lock_interruptible(&doe_mb->lock);
> > + if (rc)
> > + return rc;
> > + exec_task(task);
> > + mutex_unlock(&doe_mb->lock);
> > +
> > return 0;
> > }
> > -EXPORT_SYMBOL_GPL(pci_doe_submit_task);
> > +EXPORT_SYMBOL_GPL(pci_doe_submit_task_wait);
> > diff --git a/include/linux/pci-doe.h b/include/linux/pci-doe.h
> > index ed9b4df792b8..55e6e45b87f3 100644
> > --- a/include/linux/pci-doe.h
> > +++ b/include/linux/pci-doe.h
> > @@ -29,9 +29,6 @@ struct pci_doe_mb;
> > * @response_pl: The response payload
> > * @response_pl_sz: Size of the response payload (bytes)
> > * @rv: Return value. Length of received response or error (bytes)
> > - * @complete: Called when task is complete
> > - * @private: Private data for the consumer
> > - * @work: Used internally by the mailbox
> > * @doe_mb: Used internally by the mailbox
> > *
> > * The payload sizes and rv are specified in bytes with the following
> > @@ -50,11 +47,6 @@ struct pci_doe_task {
> > u32 *response_pl;
> > size_t response_pl_sz;
> > int rv;
> > - void (*complete)(struct pci_doe_task *task);
> > - void *private;
> > -
> > - /* No need for the user to initialize these fields */
> > - struct work_struct work;
> > struct pci_doe_mb *doe_mb;
> > };
> >
> > @@ -72,6 +64,5 @@ struct pci_doe_task {
> >
> > struct pci_doe_mb *pcim_doe_create_mb(struct pci_dev *pdev, u16 cap_offset);
> > bool pci_doe_supports_prot(struct pci_doe_mb *doe_mb, u16 vid, u8 type);
> > -int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task);
> > -
> > +int pci_doe_submit_task_wait(struct pci_doe_mb *doe_mb, struct pci_doe_task *task);
> > #endif
> > --
> > 2.37.2
> >
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