2021-01-08 23:41:18

by Asmaa Mnebhi

Subject: ipmi_msghandler.c question

Hi Corey,

I have a question for you related to the following function in ipmi_msghandler.c

static void __get_guid(struct ipmi_smi *intf)
{
int rv;
struct bmc_device *bmc = intf->bmc;

bmc->dyn_guid_set = 2;
intf->null_user_handler = guid_handler;
rv = send_guid_cmd(intf, 0);
if (rv)
/* Send failed, no GUID available. */
bmc->dyn_guid_set = 0;
else
wait_event(intf->waitq, bmc->dyn_guid_set != 2);

/* dyn_guid_set makes the guid data available. */
smp_rmb();

intf->null_user_handler = NULL;
}

Why is wait_event used as opposed to wait_event_timeout? In the context where the dyn_guid_set value doesn't change from 2, this would run forever. Wouldn't we want to timeout after a certain amount of time?

Thanks.
Asmaa

2021-01-09 02:32:32

by Corey Minyard

Subject: Re: ipmi_msghandler.c question

On Fri, Jan 08, 2021 at 11:37:04PM +0000, Asmaa Mnebhi wrote:
> Hi Corey,
>
> I have a question for you related to the following function in ipmi_msghandler.c
>
> static void __get_guid(struct ipmi_smi *intf)
> {
> int rv;
> struct bmc_device *bmc = intf->bmc;
>
> bmc->dyn_guid_set = 2;
> intf->null_user_handler = guid_handler;
> rv = send_guid_cmd(intf, 0);
> if (rv)
> /* Send failed, no GUID available. */
> bmc->dyn_guid_set = 0;
> else
> wait_event(intf->waitq, bmc->dyn_guid_set != 2);
>
> /* dyn_guid_set makes the guid data available. */
> smp_rmb();
>
> intf->null_user_handler = NULL;
> }
>
> Why is wait_event used as opposed to wait_event_timeout? In the context where the dyn_guid_set value doesn't change from 2, this would run forever. Wouldn't we want to timeout after a certain amount of time?
>

The low-level IPMI driver is guarateed to return a response to a
message, though if something goes wrong with the BMC it can take a few
seconds to return the failure message. So it shouldn't be an issue.

-corey

> Thanks.
> Asmaa