RE: [PATCH] PCI: hv: Warn when wait_for_response() waits indefinitely

[Michael Kelley]

From: Long Li <longli@xxxxxxxxxxxxx> Sent: Tuesday, August 25, 2026 10:01 AM

[snip]

> >
> > Basically something like this:
> >
> > #define PCI_RESPONSE_WARN_TIMEOUT_SEC 300
> >
> > static int wait_for_response(struct hv_device *hdev,
> >                   struct completion *comp) {
> >      unsigned long warn_at =
> >          jiffies + secs_to_jiffies(PCI_RESPONSE_WARN_TIMEOUT_SEC);
> >      bool warned = false;
> >
> >      while (true) {
> >          if (hdev->channel->rescind) {
> >              dev_warn_once(&hdev->device, "The device is gone.\n");
> >              return -ENODEV;
> >          }
> >
> >          if (wait_for_completion_timeout(comp, HZ / 10)) {
> >              if (warned || time_after_eq(jiffies, warn_at))
> >                  dev_warn(&hdev->device,
> >                       "PCI response received after prolonged wait.\n");
> >              return 0;
> >          }
> >
> >          if (!warned && time_after_eq(jiffies, warn_at)) {
> >              dev_warn(&hdev->device,
> >                   "PCI still waiting for response.\n");
> >              warned = true;
> >          }
> >      }
> > }
> >
> > Regards,
> > Naman
> 
> This looks better.
> 

I like getting the "response received" message if the response
eventually does come in. It's a judgment call, but I would be OK
with outputting the "still waiting" message after each wait interval
rather than doing it only once. And I would make the interval smaller
than 300 seconds. Five minutes is a long time to wait and wonder
what's going on when things are hung. 60 or 120 seconds would
be OK -- a line in dmesg every 1 or 2 minutes doesn't seem like
spamming to me when something is fundamentally broken.
And probably don't expect a VM in this broken state to keep running
for hours -- the sysadmin or automatic monitoring software will
reboot it to get it working again.

Just my $.02. Outputting the "still waiting" message only once is
also OK. Your call.

Michael