From: Ira Weiny <[email protected]>
The callers of pci_doe_submit_task() allocate the pci_doe_task on the
stack. This causes the work structure to be allocated on the stack
without pci_doe_submit_task() knowing. Work item initialization needs
to be done with either INIT_WORK_ONSTACK() or INIT_WORK() depending on
how the work item is allocated.
Jonathan suggested creating doe task allocation macros such as
DECLARE_CDAT_DOE_TASK_ONSTACK().[1] The issue with this is the work
function is not known to the callers and must be initialized correctly.
A follow up suggestion was to have an internal 'pci_doe_work' item
allocated by pci_doe_submit_task().[2] This requires an allocation which
could restrict the context where tasks are used.
Compromise with an intermediate step to initialize the task struct with
a new call pci_doe_init_task() which must be called prior to submit
task.
[1] https://lore.kernel.org/linux-cxl/[email protected]/T/#m88a7f50dcce52f30c8bf5c3dcc06fa9843b54a2d
[2] https://lore.kernel.org/linux-cxl/[email protected]/T/#m63c636c5135f304480370924f4d03c00357be667
Cc: Bjorn Helgaas <[email protected]>
Reported-by: Gregory Price <[email protected]>
Reported-by: Jonathan Cameron <[email protected]>
Suggested-by: Dan Williams <[email protected]>
Signed-off-by: Ira Weiny <[email protected]>
---
drivers/cxl/core/pci.c | 2 ++
drivers/pci/doe.c | 14 ++++++++++++--
include/linux/pci-doe.h | 8 +++++---
3 files changed, 19 insertions(+), 5 deletions(-)
diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
index 9240df53ed87..a19c1fa0e2f4 100644
--- a/drivers/cxl/core/pci.c
+++ b/drivers/cxl/core/pci.c
@@ -525,6 +525,7 @@ static int cxl_cdat_get_length(struct device *dev,
DECLARE_CDAT_DOE_TASK(CDAT_DOE_REQ(0), t);
int rc;
+ pci_doe_init_task(cdat_doe, &t.task, true);
rc = pci_doe_submit_task(cdat_doe, &t.task);
if (rc < 0) {
dev_err(dev, "DOE submit failed: %d", rc);
@@ -554,6 +555,7 @@ static int cxl_cdat_read_table(struct device *dev,
u32 *entry;
int rc;
+ pci_doe_init_task(cdat_doe, &t.task, true);
rc = pci_doe_submit_task(cdat_doe, &t.task);
if (rc < 0) {
dev_err(dev, "DOE submit failed: %d", rc);
diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
index e402f05068a5..cabeae4ae955 100644
--- a/drivers/pci/doe.c
+++ b/drivers/pci/doe.c
@@ -319,6 +319,7 @@ static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 *index, u16 *vid,
};
int rc;
+ pci_doe_init_task(doe_mb, &task, true);
rc = pci_doe_submit_task(doe_mb, &task);
if (rc < 0)
return rc;
@@ -495,6 +496,14 @@ bool pci_doe_supports_prot(struct pci_doe_mb *doe_mb, u16 vid, u8 type)
}
EXPORT_SYMBOL_GPL(pci_doe_supports_prot);
+void pci_doe_init_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task,
+ bool onstack)
+{
+ task->doe_mb = doe_mb;
+ __INIT_WORK(&task->work, doe_statemachine_work, onstack);
+}
+EXPORT_SYMBOL_GPL(pci_doe_init_task);
+
/**
* pci_doe_submit_task() - Submit a task to be processed by the state machine
*
@@ -517,6 +526,9 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
if (!pci_doe_supports_prot(doe_mb, task->prot.vid, task->prot.type))
return -EINVAL;
+ if (WARN_ON_ONCE(task->work.func != doe_statemachine_work))
+ return -EINVAL;
+
/*
* DOE requests must be a whole number of DW and the response needs to
* be big enough for at least 1 DW
@@ -528,8 +540,6 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
if (test_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags))
return -EIO;
- task->doe_mb = doe_mb;
- INIT_WORK(&task->work, doe_statemachine_work);
queue_work(doe_mb->work_queue, &task->work);
return 0;
}
diff --git a/include/linux/pci-doe.h b/include/linux/pci-doe.h
index ed9b4df792b8..457fc0e53d64 100644
--- a/include/linux/pci-doe.h
+++ b/include/linux/pci-doe.h
@@ -31,8 +31,8 @@ struct pci_doe_mb;
* @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
+ * @work: Used internally by the mailbox [see pci_doe_init_task()]
+ * @doe_mb: Used internally by the mailbox [see pci_doe_init_task()]
*
* The payload sizes and rv are specified in bytes with the following
* restrictions concerning the protocol.
@@ -53,7 +53,7 @@ struct pci_doe_task {
void (*complete)(struct pci_doe_task *task);
void *private;
- /* No need for the user to initialize these fields */
+ /* Call pci_doe_init_task() for these */
struct work_struct work;
struct pci_doe_mb *doe_mb;
};
@@ -72,6 +72,8 @@ 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);
+void pci_doe_init_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task,
+ bool onstack);
int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task);
#endif
base-commit: 30a0b95b1335e12efef89dd78518ed3e4a71a763
--
2.37.2
On Mon, 14 Nov 2022 17:19:43 -0800
[email protected] wrote:
> From: Ira Weiny <[email protected]>
>
> The callers of pci_doe_submit_task() allocate the pci_doe_task on the
> stack. This causes the work structure to be allocated on the stack
> without pci_doe_submit_task() knowing. Work item initialization needs
> to be done with either INIT_WORK_ONSTACK() or INIT_WORK() depending on
> how the work item is allocated.
>
> Jonathan suggested creating doe task allocation macros such as
> DECLARE_CDAT_DOE_TASK_ONSTACK().[1] The issue with this is the work
> function is not known to the callers and must be initialized correctly.
>
> A follow up suggestion was to have an internal 'pci_doe_work' item
> allocated by pci_doe_submit_task().[2] This requires an allocation which
> could restrict the context where tasks are used.
>
> Compromise with an intermediate step to initialize the task struct with
> a new call pci_doe_init_task() which must be called prior to submit
> task.
>
> [1] https://lore.kernel.org/linux-cxl/[email protected]/T/#m88a7f50dcce52f30c8bf5c3dcc06fa9843b54a2d
> [2] https://lore.kernel.org/linux-cxl/[email protected]/T/#m63c636c5135f304480370924f4d03c00357be667
>
> Cc: Bjorn Helgaas <[email protected]>
> Reported-by: Gregory Price <[email protected]>
> Reported-by: Jonathan Cameron <[email protected]>
> Suggested-by: Dan Williams <[email protected]>
> Signed-off-by: Ira Weiny <[email protected]>
Looks like a good solution to me.
Reviewed-by: Jonathan Cameron <[email protected]>
> ---
> drivers/cxl/core/pci.c | 2 ++
> drivers/pci/doe.c | 14 ++++++++++++--
> include/linux/pci-doe.h | 8 +++++---
> 3 files changed, 19 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index 9240df53ed87..a19c1fa0e2f4 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -525,6 +525,7 @@ static int cxl_cdat_get_length(struct device *dev,
> DECLARE_CDAT_DOE_TASK(CDAT_DOE_REQ(0), t);
> int rc;
>
> + pci_doe_init_task(cdat_doe, &t.task, true);
> rc = pci_doe_submit_task(cdat_doe, &t.task);
> if (rc < 0) {
> dev_err(dev, "DOE submit failed: %d", rc);
> @@ -554,6 +555,7 @@ static int cxl_cdat_read_table(struct device *dev,
> u32 *entry;
> int rc;
>
> + pci_doe_init_task(cdat_doe, &t.task, true);
> rc = pci_doe_submit_task(cdat_doe, &t.task);
> if (rc < 0) {
> dev_err(dev, "DOE submit failed: %d", rc);
> diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
> index e402f05068a5..cabeae4ae955 100644
> --- a/drivers/pci/doe.c
> +++ b/drivers/pci/doe.c
> @@ -319,6 +319,7 @@ static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 *index, u16 *vid,
> };
> int rc;
>
> + pci_doe_init_task(doe_mb, &task, true);
> rc = pci_doe_submit_task(doe_mb, &task);
> if (rc < 0)
> return rc;
> @@ -495,6 +496,14 @@ bool pci_doe_supports_prot(struct pci_doe_mb *doe_mb, u16 vid, u8 type)
> }
> EXPORT_SYMBOL_GPL(pci_doe_supports_prot);
>
> +void pci_doe_init_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task,
> + bool onstack)
> +{
> + task->doe_mb = doe_mb;
> + __INIT_WORK(&task->work, doe_statemachine_work, onstack);
> +}
> +EXPORT_SYMBOL_GPL(pci_doe_init_task);
> +
> /**
> * pci_doe_submit_task() - Submit a task to be processed by the state machine
> *
> @@ -517,6 +526,9 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> if (!pci_doe_supports_prot(doe_mb, task->prot.vid, task->prot.type))
> return -EINVAL;
>
> + if (WARN_ON_ONCE(task->work.func != doe_statemachine_work))
> + return -EINVAL;
> +
> /*
> * DOE requests must be a whole number of DW and the response needs to
> * be big enough for at least 1 DW
> @@ -528,8 +540,6 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> if (test_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags))
> return -EIO;
>
> - task->doe_mb = doe_mb;
> - INIT_WORK(&task->work, doe_statemachine_work);
> queue_work(doe_mb->work_queue, &task->work);
> return 0;
> }
> diff --git a/include/linux/pci-doe.h b/include/linux/pci-doe.h
> index ed9b4df792b8..457fc0e53d64 100644
> --- a/include/linux/pci-doe.h
> +++ b/include/linux/pci-doe.h
> @@ -31,8 +31,8 @@ struct pci_doe_mb;
> * @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
> + * @work: Used internally by the mailbox [see pci_doe_init_task()]
> + * @doe_mb: Used internally by the mailbox [see pci_doe_init_task()]
> *
> * The payload sizes and rv are specified in bytes with the following
> * restrictions concerning the protocol.
> @@ -53,7 +53,7 @@ struct pci_doe_task {
> void (*complete)(struct pci_doe_task *task);
> void *private;
>
> - /* No need for the user to initialize these fields */
> + /* Call pci_doe_init_task() for these */
> struct work_struct work;
> struct pci_doe_mb *doe_mb;
> };
> @@ -72,6 +72,8 @@ 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);
> +void pci_doe_init_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task,
> + bool onstack);
> int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task);
>
> #endif
>
> base-commit: 30a0b95b1335e12efef89dd78518ed3e4a71a763
Hi Ira,
Can you fix the subject to follow capitalization convention (use "git
log --oneline") and say something more specific than "fix struct"?
On Mon, Nov 14, 2022 at 05:19:43PM -0800, [email protected] wrote:
> From: Ira Weiny <[email protected]>
>
> The callers of pci_doe_submit_task() allocate the pci_doe_task on the
> stack. This causes the work structure to be allocated on the stack
> without pci_doe_submit_task() knowing. Work item initialization needs
> to be done with either INIT_WORK_ONSTACK() or INIT_WORK() depending on
> how the work item is allocated.
>
> Jonathan suggested creating doe task allocation macros such as
> DECLARE_CDAT_DOE_TASK_ONSTACK().[1] The issue with this is the work
> function is not known to the callers and must be initialized correctly.
>
> A follow up suggestion was to have an internal 'pci_doe_work' item
> allocated by pci_doe_submit_task().[2] This requires an allocation which
> could restrict the context where tasks are used.
>
> Compromise with an intermediate step to initialize the task struct with
> a new call pci_doe_init_task() which must be called prior to submit
> task.
I'm not really a fan of passing a parameter to say "this struct is on
the stack" because that seems kind of error-prone and I don't know
what the consequence of getting it wrong would be. Sounds like it
*could* be some memory corruption or reading garbage data that would
be hard to debug.
Do we have cases today where pci_doe_submit_task() can't do the
kzalloc() as in your patch at [3]? If the current use cases allow a
kzalloc(), why not do that now and defer this until it becomes an
issue?
Bjorn
> [1] https://lore.kernel.org/linux-cxl/[email protected]/T/#m88a7f50dcce52f30c8bf5c3dcc06fa9843b54a2d
> [2] https://lore.kernel.org/linux-cxl/[email protected]/T/#m63c636c5135f304480370924f4d03c00357be667
[3] https://lore.kernel.org/linux-cxl/Y2AnKB88ALYm9c5L@iweiny-desk3/
> Cc: Bjorn Helgaas <[email protected]>
> Reported-by: Gregory Price <[email protected]>
> Reported-by: Jonathan Cameron <[email protected]>
> Suggested-by: Dan Williams <[email protected]>
> Signed-off-by: Ira Weiny <[email protected]>
> ---
> drivers/cxl/core/pci.c | 2 ++
> drivers/pci/doe.c | 14 ++++++++++++--
> include/linux/pci-doe.h | 8 +++++---
> 3 files changed, 19 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index 9240df53ed87..a19c1fa0e2f4 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -525,6 +525,7 @@ static int cxl_cdat_get_length(struct device *dev,
> DECLARE_CDAT_DOE_TASK(CDAT_DOE_REQ(0), t);
> int rc;
>
> + pci_doe_init_task(cdat_doe, &t.task, true);
> rc = pci_doe_submit_task(cdat_doe, &t.task);
> if (rc < 0) {
> dev_err(dev, "DOE submit failed: %d", rc);
> @@ -554,6 +555,7 @@ static int cxl_cdat_read_table(struct device *dev,
> u32 *entry;
> int rc;
>
> + pci_doe_init_task(cdat_doe, &t.task, true);
> rc = pci_doe_submit_task(cdat_doe, &t.task);
> if (rc < 0) {
> dev_err(dev, "DOE submit failed: %d", rc);
> diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
> index e402f05068a5..cabeae4ae955 100644
> --- a/drivers/pci/doe.c
> +++ b/drivers/pci/doe.c
> @@ -319,6 +319,7 @@ static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 *index, u16 *vid,
> };
> int rc;
>
> + pci_doe_init_task(doe_mb, &task, true);
> rc = pci_doe_submit_task(doe_mb, &task);
> if (rc < 0)
> return rc;
> @@ -495,6 +496,14 @@ bool pci_doe_supports_prot(struct pci_doe_mb *doe_mb, u16 vid, u8 type)
> }
> EXPORT_SYMBOL_GPL(pci_doe_supports_prot);
>
> +void pci_doe_init_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task,
> + bool onstack)
> +{
> + task->doe_mb = doe_mb;
> + __INIT_WORK(&task->work, doe_statemachine_work, onstack);
> +}
> +EXPORT_SYMBOL_GPL(pci_doe_init_task);
> +
> /**
> * pci_doe_submit_task() - Submit a task to be processed by the state machine
> *
> @@ -517,6 +526,9 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> if (!pci_doe_supports_prot(doe_mb, task->prot.vid, task->prot.type))
> return -EINVAL;
>
> + if (WARN_ON_ONCE(task->work.func != doe_statemachine_work))
> + return -EINVAL;
> +
> /*
> * DOE requests must be a whole number of DW and the response needs to
> * be big enough for at least 1 DW
> @@ -528,8 +540,6 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> if (test_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags))
> return -EIO;
>
> - task->doe_mb = doe_mb;
> - INIT_WORK(&task->work, doe_statemachine_work);
> queue_work(doe_mb->work_queue, &task->work);
> return 0;
> }
> diff --git a/include/linux/pci-doe.h b/include/linux/pci-doe.h
> index ed9b4df792b8..457fc0e53d64 100644
> --- a/include/linux/pci-doe.h
> +++ b/include/linux/pci-doe.h
> @@ -31,8 +31,8 @@ struct pci_doe_mb;
> * @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
> + * @work: Used internally by the mailbox [see pci_doe_init_task()]
> + * @doe_mb: Used internally by the mailbox [see pci_doe_init_task()]
> *
> * The payload sizes and rv are specified in bytes with the following
> * restrictions concerning the protocol.
> @@ -53,7 +53,7 @@ struct pci_doe_task {
> void (*complete)(struct pci_doe_task *task);
> void *private;
>
> - /* No need for the user to initialize these fields */
> + /* Call pci_doe_init_task() for these */
> struct work_struct work;
> struct pci_doe_mb *doe_mb;
> };
> @@ -72,6 +72,8 @@ 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);
> +void pci_doe_init_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task,
> + bool onstack);
> int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task);
>
> #endif
>
> base-commit: 30a0b95b1335e12efef89dd78518ed3e4a71a763
> --
> 2.37.2
>
On Tue, Nov 15, 2022 at 01:44:24PM -0600, Bjorn Helgaas wrote:
> Hi Ira,
>
> Can you fix the subject to follow capitalization convention (use "git
> log --oneline")
>
My apologies. I should have capitalized DOE.
>
> and say something more specific than "fix struct"?
How about?
PCI/DOE: Fix initialization of work struct in pci_doe_task
Thanks for the review,
Ira
>
> On Mon, Nov 14, 2022 at 05:19:43PM -0800, [email protected] wrote:
> > From: Ira Weiny <[email protected]>
> >
> > The callers of pci_doe_submit_task() allocate the pci_doe_task on the
> > stack. This causes the work structure to be allocated on the stack
> > without pci_doe_submit_task() knowing. Work item initialization needs
> > to be done with either INIT_WORK_ONSTACK() or INIT_WORK() depending on
> > how the work item is allocated.
> >
> > Jonathan suggested creating doe task allocation macros such as
> > DECLARE_CDAT_DOE_TASK_ONSTACK().[1] The issue with this is the work
> > function is not known to the callers and must be initialized correctly.
> >
> > A follow up suggestion was to have an internal 'pci_doe_work' item
> > allocated by pci_doe_submit_task().[2] This requires an allocation which
> > could restrict the context where tasks are used.
> >
> > Compromise with an intermediate step to initialize the task struct with
> > a new call pci_doe_init_task() which must be called prior to submit
> > task.
>
> I'm not really a fan of passing a parameter to say "this struct is on
> the stack" because that seems kind of error-prone and I don't know
> what the consequence of getting it wrong would be. Sounds like it
> *could* be some memory corruption or reading garbage data that would
> be hard to debug.
>
> Do we have cases today where pci_doe_submit_task() can't do the
> kzalloc() as in your patch at [3]? If the current use cases allow a
> kzalloc(), why not do that now and defer this until it becomes an
> issue?
>
> Bjorn
>
> > [1] https://lore.kernel.org/linux-cxl/[email protected]/T/#m88a7f50dcce52f30c8bf5c3dcc06fa9843b54a2d
> > [2] https://lore.kernel.org/linux-cxl/[email protected]/T/#m63c636c5135f304480370924f4d03c00357be667
>
> [3] https://lore.kernel.org/linux-cxl/Y2AnKB88ALYm9c5L@iweiny-desk3/
>
> > Cc: Bjorn Helgaas <[email protected]>
> > Reported-by: Gregory Price <[email protected]>
> > Reported-by: Jonathan Cameron <[email protected]>
> > Suggested-by: Dan Williams <[email protected]>
> > Signed-off-by: Ira Weiny <[email protected]>
> > ---
> > drivers/cxl/core/pci.c | 2 ++
> > drivers/pci/doe.c | 14 ++++++++++++--
> > include/linux/pci-doe.h | 8 +++++---
> > 3 files changed, 19 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> > index 9240df53ed87..a19c1fa0e2f4 100644
> > --- a/drivers/cxl/core/pci.c
> > +++ b/drivers/cxl/core/pci.c
> > @@ -525,6 +525,7 @@ static int cxl_cdat_get_length(struct device *dev,
> > DECLARE_CDAT_DOE_TASK(CDAT_DOE_REQ(0), t);
> > int rc;
> >
> > + pci_doe_init_task(cdat_doe, &t.task, true);
> > rc = pci_doe_submit_task(cdat_doe, &t.task);
> > if (rc < 0) {
> > dev_err(dev, "DOE submit failed: %d", rc);
> > @@ -554,6 +555,7 @@ static int cxl_cdat_read_table(struct device *dev,
> > u32 *entry;
> > int rc;
> >
> > + pci_doe_init_task(cdat_doe, &t.task, true);
> > rc = pci_doe_submit_task(cdat_doe, &t.task);
> > if (rc < 0) {
> > dev_err(dev, "DOE submit failed: %d", rc);
> > diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
> > index e402f05068a5..cabeae4ae955 100644
> > --- a/drivers/pci/doe.c
> > +++ b/drivers/pci/doe.c
> > @@ -319,6 +319,7 @@ static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 *index, u16 *vid,
> > };
> > int rc;
> >
> > + pci_doe_init_task(doe_mb, &task, true);
> > rc = pci_doe_submit_task(doe_mb, &task);
> > if (rc < 0)
> > return rc;
> > @@ -495,6 +496,14 @@ bool pci_doe_supports_prot(struct pci_doe_mb *doe_mb, u16 vid, u8 type)
> > }
> > EXPORT_SYMBOL_GPL(pci_doe_supports_prot);
> >
> > +void pci_doe_init_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task,
> > + bool onstack)
> > +{
> > + task->doe_mb = doe_mb;
> > + __INIT_WORK(&task->work, doe_statemachine_work, onstack);
> > +}
> > +EXPORT_SYMBOL_GPL(pci_doe_init_task);
> > +
> > /**
> > * pci_doe_submit_task() - Submit a task to be processed by the state machine
> > *
> > @@ -517,6 +526,9 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> > if (!pci_doe_supports_prot(doe_mb, task->prot.vid, task->prot.type))
> > return -EINVAL;
> >
> > + if (WARN_ON_ONCE(task->work.func != doe_statemachine_work))
> > + return -EINVAL;
> > +
> > /*
> > * DOE requests must be a whole number of DW and the response needs to
> > * be big enough for at least 1 DW
> > @@ -528,8 +540,6 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> > if (test_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags))
> > return -EIO;
> >
> > - task->doe_mb = doe_mb;
> > - INIT_WORK(&task->work, doe_statemachine_work);
> > queue_work(doe_mb->work_queue, &task->work);
> > return 0;
> > }
> > diff --git a/include/linux/pci-doe.h b/include/linux/pci-doe.h
> > index ed9b4df792b8..457fc0e53d64 100644
> > --- a/include/linux/pci-doe.h
> > +++ b/include/linux/pci-doe.h
> > @@ -31,8 +31,8 @@ struct pci_doe_mb;
> > * @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
> > + * @work: Used internally by the mailbox [see pci_doe_init_task()]
> > + * @doe_mb: Used internally by the mailbox [see pci_doe_init_task()]
> > *
> > * The payload sizes and rv are specified in bytes with the following
> > * restrictions concerning the protocol.
> > @@ -53,7 +53,7 @@ struct pci_doe_task {
> > void (*complete)(struct pci_doe_task *task);
> > void *private;
> >
> > - /* No need for the user to initialize these fields */
> > + /* Call pci_doe_init_task() for these */
> > struct work_struct work;
> > struct pci_doe_mb *doe_mb;
> > };
> > @@ -72,6 +72,8 @@ 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);
> > +void pci_doe_init_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task,
> > + bool onstack);
> > int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task);
> >
> > #endif
> >
> > base-commit: 30a0b95b1335e12efef89dd78518ed3e4a71a763
> > --
> > 2.37.2
> >
On Tue, Nov 15, 2022 at 12:18:38PM -0800, Ira Weiny wrote:
> On Tue, Nov 15, 2022 at 01:44:24PM -0600, Bjorn Helgaas wrote:
> > and say something more specific than "fix struct"?
>
> How about?
>
> PCI/DOE: Fix initialization of work struct in pci_doe_task
The importance of this has to do with whether something is on the
stack, so I think something about that would be useful.
I'm afraid this subject line bike-shedding has made you overlook my
other questions below ...
> > On Mon, Nov 14, 2022 at 05:19:43PM -0800, [email protected] wrote:
> > > From: Ira Weiny <[email protected]>
> > >
> > > The callers of pci_doe_submit_task() allocate the pci_doe_task on the
> > > stack. This causes the work structure to be allocated on the stack
> > > without pci_doe_submit_task() knowing. Work item initialization needs
> > > to be done with either INIT_WORK_ONSTACK() or INIT_WORK() depending on
> > > how the work item is allocated.
> > >
> > > Jonathan suggested creating doe task allocation macros such as
> > > DECLARE_CDAT_DOE_TASK_ONSTACK().[1] The issue with this is the work
> > > function is not known to the callers and must be initialized correctly.
> > >
> > > A follow up suggestion was to have an internal 'pci_doe_work' item
> > > allocated by pci_doe_submit_task().[2] This requires an allocation which
> > > could restrict the context where tasks are used.
> > >
> > > Compromise with an intermediate step to initialize the task struct with
> > > a new call pci_doe_init_task() which must be called prior to submit
> > > task.
> >
> > I'm not really a fan of passing a parameter to say "this struct is on
> > the stack" because that seems kind of error-prone and I don't know
> > what the consequence of getting it wrong would be. Sounds like it
> > *could* be some memory corruption or reading garbage data that would
> > be hard to debug.
> >
> > Do we have cases today where pci_doe_submit_task() can't do the
> > kzalloc() as in your patch at [3]? If the current use cases allow a
> > kzalloc(), why not do that now and defer this until it becomes an
> > issue?
> >
> > Bjorn
> >
> > > [1] https://lore.kernel.org/linux-cxl/[email protected]/T/#m88a7f50dcce52f30c8bf5c3dcc06fa9843b54a2d
> > > [2] https://lore.kernel.org/linux-cxl/[email protected]/T/#m63c636c5135f304480370924f4d03c00357be667
> >
> > [3] https://lore.kernel.org/linux-cxl/Y2AnKB88ALYm9c5L@iweiny-desk3/
> >
> > > Cc: Bjorn Helgaas <[email protected]>
> > > Reported-by: Gregory Price <[email protected]>
> > > Reported-by: Jonathan Cameron <[email protected]>
> > > Suggested-by: Dan Williams <[email protected]>
> > > Signed-off-by: Ira Weiny <[email protected]>
> > > ---
> > > drivers/cxl/core/pci.c | 2 ++
> > > drivers/pci/doe.c | 14 ++++++++++++--
> > > include/linux/pci-doe.h | 8 +++++---
> > > 3 files changed, 19 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> > > index 9240df53ed87..a19c1fa0e2f4 100644
> > > --- a/drivers/cxl/core/pci.c
> > > +++ b/drivers/cxl/core/pci.c
> > > @@ -525,6 +525,7 @@ static int cxl_cdat_get_length(struct device *dev,
> > > DECLARE_CDAT_DOE_TASK(CDAT_DOE_REQ(0), t);
> > > int rc;
> > >
> > > + pci_doe_init_task(cdat_doe, &t.task, true);
> > > rc = pci_doe_submit_task(cdat_doe, &t.task);
> > > if (rc < 0) {
> > > dev_err(dev, "DOE submit failed: %d", rc);
> > > @@ -554,6 +555,7 @@ static int cxl_cdat_read_table(struct device *dev,
> > > u32 *entry;
> > > int rc;
> > >
> > > + pci_doe_init_task(cdat_doe, &t.task, true);
> > > rc = pci_doe_submit_task(cdat_doe, &t.task);
> > > if (rc < 0) {
> > > dev_err(dev, "DOE submit failed: %d", rc);
> > > diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
> > > index e402f05068a5..cabeae4ae955 100644
> > > --- a/drivers/pci/doe.c
> > > +++ b/drivers/pci/doe.c
> > > @@ -319,6 +319,7 @@ static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 *index, u16 *vid,
> > > };
> > > int rc;
> > >
> > > + pci_doe_init_task(doe_mb, &task, true);
> > > rc = pci_doe_submit_task(doe_mb, &task);
> > > if (rc < 0)
> > > return rc;
> > > @@ -495,6 +496,14 @@ bool pci_doe_supports_prot(struct pci_doe_mb *doe_mb, u16 vid, u8 type)
> > > }
> > > EXPORT_SYMBOL_GPL(pci_doe_supports_prot);
> > >
> > > +void pci_doe_init_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task,
> > > + bool onstack)
> > > +{
> > > + task->doe_mb = doe_mb;
> > > + __INIT_WORK(&task->work, doe_statemachine_work, onstack);
> > > +}
> > > +EXPORT_SYMBOL_GPL(pci_doe_init_task);
> > > +
> > > /**
> > > * pci_doe_submit_task() - Submit a task to be processed by the state machine
> > > *
> > > @@ -517,6 +526,9 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> > > if (!pci_doe_supports_prot(doe_mb, task->prot.vid, task->prot.type))
> > > return -EINVAL;
> > >
> > > + if (WARN_ON_ONCE(task->work.func != doe_statemachine_work))
> > > + return -EINVAL;
> > > +
> > > /*
> > > * DOE requests must be a whole number of DW and the response needs to
> > > * be big enough for at least 1 DW
> > > @@ -528,8 +540,6 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> > > if (test_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags))
> > > return -EIO;
> > >
> > > - task->doe_mb = doe_mb;
> > > - INIT_WORK(&task->work, doe_statemachine_work);
> > > queue_work(doe_mb->work_queue, &task->work);
> > > return 0;
> > > }
> > > diff --git a/include/linux/pci-doe.h b/include/linux/pci-doe.h
> > > index ed9b4df792b8..457fc0e53d64 100644
> > > --- a/include/linux/pci-doe.h
> > > +++ b/include/linux/pci-doe.h
> > > @@ -31,8 +31,8 @@ struct pci_doe_mb;
> > > * @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
> > > + * @work: Used internally by the mailbox [see pci_doe_init_task()]
> > > + * @doe_mb: Used internally by the mailbox [see pci_doe_init_task()]
> > > *
> > > * The payload sizes and rv are specified in bytes with the following
> > > * restrictions concerning the protocol.
> > > @@ -53,7 +53,7 @@ struct pci_doe_task {
> > > void (*complete)(struct pci_doe_task *task);
> > > void *private;
> > >
> > > - /* No need for the user to initialize these fields */
> > > + /* Call pci_doe_init_task() for these */
> > > struct work_struct work;
> > > struct pci_doe_mb *doe_mb;
> > > };
> > > @@ -72,6 +72,8 @@ 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);
> > > +void pci_doe_init_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task,
> > > + bool onstack);
> > > int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task);
> > >
> > > #endif
> > >
> > > base-commit: 30a0b95b1335e12efef89dd78518ed3e4a71a763
> > > --
> > > 2.37.2
> > >
On Tue, Nov 15, 2022 at 02:41:35PM -0600, Bjorn Helgaas wrote:
> On Tue, Nov 15, 2022 at 12:18:38PM -0800, Ira Weiny wrote:
> > On Tue, Nov 15, 2022 at 01:44:24PM -0600, Bjorn Helgaas wrote:
> > > and say something more specific than "fix struct"?
> >
> > How about?
> >
> > PCI/DOE: Fix initialization of work struct in pci_doe_task
>
> The importance of this has to do with whether something is on the
> stack, so I think something about that would be useful.
>
> I'm afraid this subject line bike-shedding has made you overlook my
> other questions below ...
Oh... I see now.
>
> > > On Mon, Nov 14, 2022 at 05:19:43PM -0800, [email protected] wrote:
> > > > From: Ira Weiny <[email protected]>
> > > >
> > > > The callers of pci_doe_submit_task() allocate the pci_doe_task on the
> > > > stack. This causes the work structure to be allocated on the stack
> > > > without pci_doe_submit_task() knowing. Work item initialization needs
> > > > to be done with either INIT_WORK_ONSTACK() or INIT_WORK() depending on
> > > > how the work item is allocated.
> > > >
> > > > Jonathan suggested creating doe task allocation macros such as
> > > > DECLARE_CDAT_DOE_TASK_ONSTACK().[1] The issue with this is the work
> > > > function is not known to the callers and must be initialized correctly.
> > > >
> > > > A follow up suggestion was to have an internal 'pci_doe_work' item
> > > > allocated by pci_doe_submit_task().[2] This requires an allocation which
> > > > could restrict the context where tasks are used.
> > > >
> > > > Compromise with an intermediate step to initialize the task struct with
> > > > a new call pci_doe_init_task() which must be called prior to submit
> > > > task.
> > >
> > > I'm not really a fan of passing a parameter to say "this struct is on
> > > the stack" because that seems kind of error-prone and I don't know
> > > what the consequence of getting it wrong would be. Sounds like it
> > > *could* be some memory corruption or reading garbage data that would
> > > be hard to debug.
> > >
> > > Do we have cases today where pci_doe_submit_task() can't do the
> > > kzalloc() as in your patch at [3]?
No.
> > > If the current use cases allow a
> > > kzalloc(), why not do that now and defer this until it becomes an
> > > issue?
I do like pci_doe_submit_task() handling this as an internal detail. I'm happy
with that if you are.
I was just concerned about the restriction of context. Dan suggested this
instead of passing a gfp parameter.
If you are happy with my original patch I will submit it instead. (With a
better one liner.)
Thanks again for the review,
Ira
> > >
> > > Bjorn
> > >
> > > > [1] https://lore.kernel.org/linux-cxl/[email protected]/T/#m88a7f50dcce52f30c8bf5c3dcc06fa9843b54a2d
> > > > [2] https://lore.kernel.org/linux-cxl/[email protected]/T/#m63c636c5135f304480370924f4d03c00357be667
> > >
> > > [3] https://lore.kernel.org/linux-cxl/Y2AnKB88ALYm9c5L@iweiny-desk3/
> > >
> > > > Cc: Bjorn Helgaas <[email protected]>
> > > > Reported-by: Gregory Price <[email protected]>
> > > > Reported-by: Jonathan Cameron <[email protected]>
> > > > Suggested-by: Dan Williams <[email protected]>
> > > > Signed-off-by: Ira Weiny <[email protected]>
> > > > ---
> > > > drivers/cxl/core/pci.c | 2 ++
> > > > drivers/pci/doe.c | 14 ++++++++++++--
> > > > include/linux/pci-doe.h | 8 +++++---
> > > > 3 files changed, 19 insertions(+), 5 deletions(-)
> > > >
> > > > diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> > > > index 9240df53ed87..a19c1fa0e2f4 100644
> > > > --- a/drivers/cxl/core/pci.c
> > > > +++ b/drivers/cxl/core/pci.c
> > > > @@ -525,6 +525,7 @@ static int cxl_cdat_get_length(struct device *dev,
> > > > DECLARE_CDAT_DOE_TASK(CDAT_DOE_REQ(0), t);
> > > > int rc;
> > > >
> > > > + pci_doe_init_task(cdat_doe, &t.task, true);
> > > > rc = pci_doe_submit_task(cdat_doe, &t.task);
> > > > if (rc < 0) {
> > > > dev_err(dev, "DOE submit failed: %d", rc);
> > > > @@ -554,6 +555,7 @@ static int cxl_cdat_read_table(struct device *dev,
> > > > u32 *entry;
> > > > int rc;
> > > >
> > > > + pci_doe_init_task(cdat_doe, &t.task, true);
> > > > rc = pci_doe_submit_task(cdat_doe, &t.task);
> > > > if (rc < 0) {
> > > > dev_err(dev, "DOE submit failed: %d", rc);
> > > > diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
> > > > index e402f05068a5..cabeae4ae955 100644
> > > > --- a/drivers/pci/doe.c
> > > > +++ b/drivers/pci/doe.c
> > > > @@ -319,6 +319,7 @@ static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 *index, u16 *vid,
> > > > };
> > > > int rc;
> > > >
> > > > + pci_doe_init_task(doe_mb, &task, true);
> > > > rc = pci_doe_submit_task(doe_mb, &task);
> > > > if (rc < 0)
> > > > return rc;
> > > > @@ -495,6 +496,14 @@ bool pci_doe_supports_prot(struct pci_doe_mb *doe_mb, u16 vid, u8 type)
> > > > }
> > > > EXPORT_SYMBOL_GPL(pci_doe_supports_prot);
> > > >
> > > > +void pci_doe_init_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task,
> > > > + bool onstack)
> > > > +{
> > > > + task->doe_mb = doe_mb;
> > > > + __INIT_WORK(&task->work, doe_statemachine_work, onstack);
> > > > +}
> > > > +EXPORT_SYMBOL_GPL(pci_doe_init_task);
> > > > +
> > > > /**
> > > > * pci_doe_submit_task() - Submit a task to be processed by the state machine
> > > > *
> > > > @@ -517,6 +526,9 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> > > > if (!pci_doe_supports_prot(doe_mb, task->prot.vid, task->prot.type))
> > > > return -EINVAL;
> > > >
> > > > + if (WARN_ON_ONCE(task->work.func != doe_statemachine_work))
> > > > + return -EINVAL;
> > > > +
> > > > /*
> > > > * DOE requests must be a whole number of DW and the response needs to
> > > > * be big enough for at least 1 DW
> > > > @@ -528,8 +540,6 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> > > > if (test_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags))
> > > > return -EIO;
> > > >
> > > > - task->doe_mb = doe_mb;
> > > > - INIT_WORK(&task->work, doe_statemachine_work);
> > > > queue_work(doe_mb->work_queue, &task->work);
> > > > return 0;
> > > > }
> > > > diff --git a/include/linux/pci-doe.h b/include/linux/pci-doe.h
> > > > index ed9b4df792b8..457fc0e53d64 100644
> > > > --- a/include/linux/pci-doe.h
> > > > +++ b/include/linux/pci-doe.h
> > > > @@ -31,8 +31,8 @@ struct pci_doe_mb;
> > > > * @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
> > > > + * @work: Used internally by the mailbox [see pci_doe_init_task()]
> > > > + * @doe_mb: Used internally by the mailbox [see pci_doe_init_task()]
> > > > *
> > > > * The payload sizes and rv are specified in bytes with the following
> > > > * restrictions concerning the protocol.
> > > > @@ -53,7 +53,7 @@ struct pci_doe_task {
> > > > void (*complete)(struct pci_doe_task *task);
> > > > void *private;
> > > >
> > > > - /* No need for the user to initialize these fields */
> > > > + /* Call pci_doe_init_task() for these */
> > > > struct work_struct work;
> > > > struct pci_doe_mb *doe_mb;
> > > > };
> > > > @@ -72,6 +72,8 @@ 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);
> > > > +void pci_doe_init_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task,
> > > > + bool onstack);
> > > > int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task);
> > > >
> > > > #endif
> > > >
> > > > base-commit: 30a0b95b1335e12efef89dd78518ed3e4a71a763
> > > > --
> > > > 2.37.2
> > > >
On Tue, Nov 15, 2022 at 12:54:39PM -0800, Ira Weiny wrote:
> On Tue, Nov 15, 2022 at 02:41:35PM -0600, Bjorn Helgaas wrote:
> > On Tue, Nov 15, 2022 at 12:18:38PM -0800, Ira Weiny wrote:
> > > On Tue, Nov 15, 2022 at 01:44:24PM -0600, Bjorn Helgaas wrote:
> > > > On Mon, Nov 14, 2022 at 05:19:43PM -0800, [email protected] wrote:
> > > > > From: Ira Weiny <[email protected]>
> > > > >
> > > > > The callers of pci_doe_submit_task() allocate the
> > > > > pci_doe_task on the stack. This causes the work structure
> > > > > to be allocated on the stack without pci_doe_submit_task()
> > > > > knowing. Work item initialization needs to be done with
> > > > > either INIT_WORK_ONSTACK() or INIT_WORK() depending on how
> > > > > the work item is allocated.
> > > > >
> > > > > Jonathan suggested creating doe task allocation macros such
> > > > > as DECLARE_CDAT_DOE_TASK_ONSTACK().[1] The issue with this
> > > > > is the work function is not known to the callers and must be
> > > > > initialized correctly.
> > > > >
> > > > > A follow up suggestion was to have an internal
> > > > > 'pci_doe_work' item allocated by pci_doe_submit_task().[2]
> > > > > This requires an allocation which could restrict the context
> > > > > where tasks are used.
> > > > >
> > > > > Compromise with an intermediate step to initialize the task
> > > > > struct with a new call pci_doe_init_task() which must be
> > > > > called prior to submit task.
> > > >
> > > > I'm not really a fan of passing a parameter to say "this struct is on
> > > > the stack" because that seems kind of error-prone and I don't know
> > > > what the consequence of getting it wrong would be. Sounds like it
> > > > *could* be some memory corruption or reading garbage data that would
> > > > be hard to debug.
> > > >
> > > > Do we have cases today where pci_doe_submit_task() can't do the
> > > > kzalloc() as in your patch at [3]?
>
> No.
>
> > > > If the current use cases allow a
> > > > kzalloc(), why not do that now and defer this until it becomes an
> > > > issue?
>
> I do like pci_doe_submit_task() handling this as an internal detail.
> I'm happy with that if you are.
>
> I was just concerned about the restriction of context. Dan
> suggested this instead of passing a gfp parameter.
>
> If you are happy with my original patch I will submit it instead.
> (With a better one liner.)
I don't know what's coming as far as pci_doe_submit_task() callers.
If there's some imminent caller that will require atomic context, I
guess we could solve it now. But DOE doesn't really seem like an
atomic context thing to begin with, so maybe we could postpone dealing
with it.
That patch in [3] is more complicated than I expected, but I admit I
haven't looked closely.
Bjorn
> > > > > [1] https://lore.kernel.org/linux-cxl/[email protected]/T/#m88a7f50dcce52f30c8bf5c3dcc06fa9843b54a2d
> > > > > [2] https://lore.kernel.org/linux-cxl/[email protected]/T/#m63c636c5135f304480370924f4d03c00357be667
> > > >
> > > > [3] https://lore.kernel.org/linux-cxl/Y2AnKB88ALYm9c5L@iweiny-desk3/
On Mon, Nov 14, 2022 at 05:19:43PM -0800, [email protected] wrote:
> From: Ira Weiny <[email protected]>
>
> The callers of pci_doe_submit_task() allocate the pci_doe_task on the
> stack. This causes the work structure to be allocated on the stack
> without pci_doe_submit_task() knowing. Work item initialization needs
> to be done with either INIT_WORK_ONSTACK() or INIT_WORK() depending on
> how the work item is allocated.
>
> Jonathan suggested creating doe task allocation macros such as
> DECLARE_CDAT_DOE_TASK_ONSTACK().[1] The issue with this is the work
> function is not known to the callers and must be initialized correctly.
>
> A follow up suggestion was to have an internal 'pci_doe_work' item
> allocated by pci_doe_submit_task().[2] This requires an allocation which
> could restrict the context where tasks are used.
>
> Compromise with an intermediate step to initialize the task struct with
> a new call pci_doe_init_task() which must be called prior to submit
> task.
>
> [1] https://lore.kernel.org/linux-cxl/[email protected]/T/#m88a7f50dcce52f30c8bf5c3dcc06fa9843b54a2d
> [2] https://lore.kernel.org/linux-cxl/[email protected]/T/#m63c636c5135f304480370924f4d03c00357be667
We have object_is_on_stack(), included from <linux/sched/task_stack.h>.
So you could just autosense in pci_doe_submit_task() whether
pci_doe_task is on the stack and call the appropriate INIT_WORK
variant.
Any reason not to do that?
Thanks,
Lukas
On Wed, Nov 16, 2022 at 11:09:39AM +0100, Lukas Wunner wrote:
> On Mon, Nov 14, 2022 at 05:19:43PM -0800, [email protected] wrote:
> > From: Ira Weiny <[email protected]>
> >
> > The callers of pci_doe_submit_task() allocate the pci_doe_task on the
> > stack. This causes the work structure to be allocated on the stack
> > without pci_doe_submit_task() knowing. Work item initialization needs
> > to be done with either INIT_WORK_ONSTACK() or INIT_WORK() depending on
> > how the work item is allocated.
> >
> > Jonathan suggested creating doe task allocation macros such as
> > DECLARE_CDAT_DOE_TASK_ONSTACK().[1] The issue with this is the work
> > function is not known to the callers and must be initialized correctly.
> >
> > A follow up suggestion was to have an internal 'pci_doe_work' item
> > allocated by pci_doe_submit_task().[2] This requires an allocation which
> > could restrict the context where tasks are used.
> >
> > Compromise with an intermediate step to initialize the task struct with
> > a new call pci_doe_init_task() which must be called prior to submit
> > task.
> >
> > [1] https://lore.kernel.org/linux-cxl/[email protected]/T/#m88a7f50dcce52f30c8bf5c3dcc06fa9843b54a2d
> > [2] https://lore.kernel.org/linux-cxl/[email protected]/T/#m63c636c5135f304480370924f4d03c00357be667
>
> We have object_is_on_stack(), included from <linux/sched/task_stack.h>.
>
> So you could just autosense in pci_doe_submit_task() whether
> pci_doe_task is on the stack and call the appropriate INIT_WORK
> variant.
Nifty, I had no idea object_is_on_stack() existed, thank you!
I wonder if there's an opportunity to use object_is_on_stack()
somewhere in the INIT_WORK() path to find usage mistakes.
Adding it in pci_doe_submit_task() would add some complexity, so I'm
not sure whether it's worth adding it unless we actually have uses for
both cases.
Bjorn
Ira Weiny wrote:
> On Wed, Nov 16, 2022 at 12:20:37PM -0600, Bjorn Helgaas wrote:
> > On Wed, Nov 16, 2022 at 11:09:39AM +0100, Lukas Wunner wrote:
> > > On Mon, Nov 14, 2022 at 05:19:43PM -0800, [email protected] wrote:
> > > > From: Ira Weiny <[email protected]>
> > > >
> > > > The callers of pci_doe_submit_task() allocate the pci_doe_task on the
> > > > stack. This causes the work structure to be allocated on the stack
> > > > without pci_doe_submit_task() knowing. Work item initialization needs
> > > > to be done with either INIT_WORK_ONSTACK() or INIT_WORK() depending on
> > > > how the work item is allocated.
> > > >
> > > > Jonathan suggested creating doe task allocation macros such as
> > > > DECLARE_CDAT_DOE_TASK_ONSTACK().[1] The issue with this is the work
> > > > function is not known to the callers and must be initialized correctly.
> > > >
> > > > A follow up suggestion was to have an internal 'pci_doe_work' item
> > > > allocated by pci_doe_submit_task().[2] This requires an allocation which
> > > > could restrict the context where tasks are used.
> > > >
> > > > Compromise with an intermediate step to initialize the task struct with
> > > > a new call pci_doe_init_task() which must be called prior to submit
> > > > task.
> > > >
> > > > [1] https://lore.kernel.org/linux-cxl/[email protected]/T/#m88a7f50dcce52f30c8bf5c3dcc06fa9843b54a2d
> > > > [2] https://lore.kernel.org/linux-cxl/[email protected]/T/#m63c636c5135f304480370924f4d03c00357be667
> > >
> > > We have object_is_on_stack(), included from <linux/sched/task_stack.h>.
> > >
> > > So you could just autosense in pci_doe_submit_task() whether
> > > pci_doe_task is on the stack and call the appropriate INIT_WORK
> > > variant.
> >
> > Nifty, I had no idea object_is_on_stack() existed, thank you!
>
> Indeed! Neither did I! thanks!
>
> >
> > I wonder if there's an opportunity to use object_is_on_stack()
> > somewhere in the INIT_WORK() path to find usage mistakes.
>
> I'm thinking we could make INIT_WORK do the right thing all the time. Not sure
> what the overhead of object_is_on_stack() is.
>
> >
> > Adding it in pci_doe_submit_task() would add some complexity, so I'm
> > not sure whether it's worth adding it unless we actually have uses for
> > both cases.
>
> I think if we don't do something we have to document that
> pci_doe_submit_task() only works with tasks on the stack.
>
> I would rather just make pci_doe_submit_task() correct and not complicate the
> callers. object_is_on_stack() can't be enough overhead to be worried about in
> this call path can it?
>
> Actually after writing all that I wonder if we can't push the use of
> object_is_on_stack() into the debug code? Something like below (completely
> untested)? I think this could be pushed even further down but I'd like to get
> opinions before attempting a change which will have a wider blast radius.
This looks reasonable, but I would do it after and independently of
introducing the autosensing version of pci_doe_submit_task(). Then you
can pursue this line of thinking and come back to simplify
pci_doe_submit_task() if it indeed moves forward.
On Wed, Nov 16, 2022 at 12:20:37PM -0600, Bjorn Helgaas wrote:
> On Wed, Nov 16, 2022 at 11:09:39AM +0100, Lukas Wunner wrote:
> > On Mon, Nov 14, 2022 at 05:19:43PM -0800, [email protected] wrote:
> > > From: Ira Weiny <[email protected]>
> > >
> > > The callers of pci_doe_submit_task() allocate the pci_doe_task on the
> > > stack. This causes the work structure to be allocated on the stack
> > > without pci_doe_submit_task() knowing. Work item initialization needs
> > > to be done with either INIT_WORK_ONSTACK() or INIT_WORK() depending on
> > > how the work item is allocated.
> > >
> > > Jonathan suggested creating doe task allocation macros such as
> > > DECLARE_CDAT_DOE_TASK_ONSTACK().[1] The issue with this is the work
> > > function is not known to the callers and must be initialized correctly.
> > >
> > > A follow up suggestion was to have an internal 'pci_doe_work' item
> > > allocated by pci_doe_submit_task().[2] This requires an allocation which
> > > could restrict the context where tasks are used.
> > >
> > > Compromise with an intermediate step to initialize the task struct with
> > > a new call pci_doe_init_task() which must be called prior to submit
> > > task.
> > >
> > > [1] https://lore.kernel.org/linux-cxl/[email protected]/T/#m88a7f50dcce52f30c8bf5c3dcc06fa9843b54a2d
> > > [2] https://lore.kernel.org/linux-cxl/[email protected]/T/#m63c636c5135f304480370924f4d03c00357be667
> >
> > We have object_is_on_stack(), included from <linux/sched/task_stack.h>.
> >
> > So you could just autosense in pci_doe_submit_task() whether
> > pci_doe_task is on the stack and call the appropriate INIT_WORK
> > variant.
>
> Nifty, I had no idea object_is_on_stack() existed, thank you!
Indeed! Neither did I! thanks!
>
> I wonder if there's an opportunity to use object_is_on_stack()
> somewhere in the INIT_WORK() path to find usage mistakes.
I'm thinking we could make INIT_WORK do the right thing all the time. Not sure
what the overhead of object_is_on_stack() is.
>
> Adding it in pci_doe_submit_task() would add some complexity, so I'm
> not sure whether it's worth adding it unless we actually have uses for
> both cases.
I think if we don't do something we have to document that
pci_doe_submit_task() only works with tasks on the stack.
I would rather just make pci_doe_submit_task() correct and not complicate the
callers. object_is_on_stack() can't be enough overhead to be worried about in
this call path can it?
Actually after writing all that I wonder if we can't push the use of
object_is_on_stack() into the debug code? Something like below (completely
untested)? I think this could be pushed even further down but I'd like to get
opinions before attempting a change which will have a wider blast radius.
Ira
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index a0143dd24430..4cc50b554a29 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -199,7 +199,7 @@ struct execute_work {
struct delayed_work n = __DELAYED_WORK_INITIALIZER(n, f, TIMER_DEFERRABLE)
#ifdef CONFIG_DEBUG_OBJECTS_WORK
-extern void __init_work(struct work_struct *work, int onstack);
+extern void __init_work(struct work_struct *work);
extern void destroy_work_on_stack(struct work_struct *work);
extern void destroy_delayed_work_on_stack(struct delayed_work *work);
static inline unsigned int work_static(struct work_struct *work)
@@ -207,7 +207,7 @@ static inline unsigned int work_static(struct work_struct *work)
return *work_data_bits(work) & WORK_STRUCT_STATIC;
}
#else
-static inline void __init_work(struct work_struct *work, int onstack) { }
+static inline void __init_work(struct work_struct *work) { }
static inline void destroy_work_on_stack(struct work_struct *work) { }
static inline void destroy_delayed_work_on_stack(struct delayed_work *work) { }
static inline unsigned int work_static(struct work_struct *work) { return 0; }
@@ -221,20 +221,20 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; }
* to generate better code.
*/
#ifdef CONFIG_LOCKDEP
-#define __INIT_WORK(_work, _func, _onstack) \
+#define __INIT_WORK(_work, _func) \
do { \
static struct lock_class_key __key; \
\
- __init_work((_work), _onstack); \
+ __init_work(_work); \
(_work)->data = (atomic_long_t) WORK_DATA_INIT(); \
lockdep_init_map(&(_work)->lockdep_map, "(work_completion)"#_work, &__key, 0); \
INIT_LIST_HEAD(&(_work)->entry); \
(_work)->func = (_func); \
} while (0)
#else
-#define __INIT_WORK(_work, _func, _onstack) \
+#define __INIT_WORK(_work, _func) \
do { \
- __init_work((_work), _onstack); \
+ __init_work(_work); \
(_work)->data = (atomic_long_t) WORK_DATA_INIT(); \
INIT_LIST_HEAD(&(_work)->entry); \
(_work)->func = (_func); \
@@ -242,10 +242,10 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; }
#endif
#define INIT_WORK(_work, _func) \
- __INIT_WORK((_work), (_func), 0)
+ __INIT_WORK((_work), (_func))
#define INIT_WORK_ONSTACK(_work, _func) \
- __INIT_WORK((_work), (_func), 1)
+ __INIT_WORK((_work), (_func))
#define __INIT_DELAYED_WORK(_work, _func, _tflags) \
do { \
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 7cd5f5e7e0a1..7d87300cfbc6 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -515,9 +515,9 @@ static inline void debug_work_deactivate(struct work_struct *work)
debug_object_deactivate(work, &work_debug_descr);
}
-void __init_work(struct work_struct *work, int onstack)
+void __init_work(struct work_struct *work)
{
- if (onstack)
+ if (object_is_on_stack(work))
debug_object_init_on_stack(work, &work_debug_descr);
else
debug_object_init(work, &work_debug_descr);