2023-06-01 15:12:29

by Manivannan Sadhasivam

Subject: [PATCH v5 4/9] PCI: endpoint: Warn and return if EPC is started/stopped multiple times

When the EPC is started or stopped multiple times from configfs, just emit
a once time warning and return. There is no need to call the EPC start/stop
functions in those cases.

Reviewed-by: Kishon Vijay Abraham I <[email protected]>
Signed-off-by: Manivannan Sadhasivam <[email protected]>
---
drivers/pci/endpoint/pci-ep-cfs.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/pci/endpoint/pci-ep-cfs.c b/drivers/pci/endpoint/pci-ep-cfs.c
index 4b8ac0ac84d5..62c8e09c59f4 100644
--- a/drivers/pci/endpoint/pci-ep-cfs.c
+++ b/drivers/pci/endpoint/pci-ep-cfs.c
@@ -178,6 +178,9 @@ static ssize_t pci_epc_start_store(struct config_item *item, const char *page,
if (kstrtobool(page, &start) < 0)
return -EINVAL;

+ if (WARN_ON_ONCE(start == epc_group->start))
+ return 0;
+
if (!start) {
pci_epc_stop(epc);
epc_group->start = 0;
--
2.25.1

2023-06-01 23:31:00

by Damien Le Moal

Subject: Re: [PATCH v5 4/9] PCI: endpoint: Warn and return if EPC is started/stopped multiple times

On 6/1/23 23:57, Manivannan Sadhasivam wrote:
> When the EPC is started or stopped multiple times from configfs, just emit
> a once time warning and return. There is no need to call the EPC start/stop
> functions in those cases.
>
> Reviewed-by: Kishon Vijay Abraham I <[email protected]>
> Signed-off-by: Manivannan Sadhasivam <[email protected]>
> ---
> drivers/pci/endpoint/pci-ep-cfs.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/pci/endpoint/pci-ep-cfs.c b/drivers/pci/endpoint/pci-ep-cfs.c
> index 4b8ac0ac84d5..62c8e09c59f4 100644
> --- a/drivers/pci/endpoint/pci-ep-cfs.c
> +++ b/drivers/pci/endpoint/pci-ep-cfs.c
> @@ -178,6 +178,9 @@ static ssize_t pci_epc_start_store(struct config_item *item, const char *page,
> if (kstrtobool(page, &start) < 0)
> return -EINVAL;
>
> + if (WARN_ON_ONCE(start == epc_group->start))
> + return 0;

WARN will dump a backtrace which is fairly scary for the user. This case is
simply a bad user manipulation of the device, so why not simply add a pr_err()
(optional) and return -EALREADY ?

> +
> if (!start) {
> pci_epc_stop(epc);
> epc_group->start = 0;

--
Damien Le Moal
Western Digital Research

2023-06-02 03:53:42

by Manivannan Sadhasivam

Subject: Re: [PATCH v5 4/9] PCI: endpoint: Warn and return if EPC is started/stopped multiple times

On Fri, Jun 02, 2023 at 08:18:58AM +0900, Damien Le Moal wrote:
> On 6/1/23 23:57, Manivannan Sadhasivam wrote:
> > When the EPC is started or stopped multiple times from configfs, just emit
> > a once time warning and return. There is no need to call the EPC start/stop
> > functions in those cases.
> >
> > Reviewed-by: Kishon Vijay Abraham I <[email protected]>
> > Signed-off-by: Manivannan Sadhasivam <[email protected]>
> > ---
> > drivers/pci/endpoint/pci-ep-cfs.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/pci/endpoint/pci-ep-cfs.c b/drivers/pci/endpoint/pci-ep-cfs.c
> > index 4b8ac0ac84d5..62c8e09c59f4 100644
> > --- a/drivers/pci/endpoint/pci-ep-cfs.c
> > +++ b/drivers/pci/endpoint/pci-ep-cfs.c
> > @@ -178,6 +178,9 @@ static ssize_t pci_epc_start_store(struct config_item *item, const char *page,
> > if (kstrtobool(page, &start) < 0)
> > return -EINVAL;
> >
> > + if (WARN_ON_ONCE(start == epc_group->start))
> > + return 0;
>
> WARN will dump a backtrace which is fairly scary for the user. This case is
> simply a bad user manipulation of the device, so why not simply add a pr_err()
> (optional) and return -EALREADY ?
>

There EPF core uses WARN_ON_ONCE in other similar places, so thought of sticking
to that pattern. But I agree, WARN_ON_ONCE is not strictly required here. Will
add a error log and return the appropriate error no.

Moreover, will push a patch later to change other instances as well.

- Mani

> > +
> > if (!start) {
> > pci_epc_stop(epc);
> > epc_group->start = 0;
>
> --
> Damien Le Moal
> Western Digital Research
>

--
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