| Message ID | 1618933459-10585-1-git-send-email-mikelley@microsoft.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | [1/1] video: hyperv_fb: Add ratelimit on error message | expand |
On Tue, Apr 20, 2021 at 08:44:19AM -0700, Michael Kelley wrote: > Due to a full ring buffer, the driver may be unable to send updates to > the Hyper-V host. But outputing the error message can make the problem > worse because console output is also typically written to the frame > buffer. As a result, in some circumstances the error message is output > continuously. > > Break the cycle by rate limiting the error message. Also output > the error code for additional diagnosability. > > Signed-off-by: Michael Kelley <mikelley@microsoft.com> Applied to hyperv-next. Thanks. > --- > drivers/video/fbdev/hyperv_fb.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c > index 4dc9077..a7e6eea 100644 > --- a/drivers/video/fbdev/hyperv_fb.c > +++ b/drivers/video/fbdev/hyperv_fb.c > @@ -308,7 +308,7 @@ static inline int synthvid_send(struct hv_device *hdev, > VM_PKT_DATA_INBAND, 0); > > if (ret) > - pr_err("Unable to send packet via vmbus\n"); > + pr_err_ratelimited("Unable to send packet via vmbus; error %d\n", ret); > > return ret; > } > -- > 1.8.3.1 >
On Tue, 2021-04-20 at 08:44 -0700, Michael Kelley wrote: > Due to a full ring buffer, the driver may be unable to send updates to > the Hyper-V host. But outputing the error message can make the problem > worse because console output is also typically written to the frame > buffer. As a result, in some circumstances the error message is output > continuously. > > Break the cycle by rate limiting the error message. Also output > the error code for additional diagnosability. > > Signed-off-by: Michael Kelley <mikelley@microsoft.com> None of the callers of this function ever check the return status. Why is important/useful to emit this message at all? > --- > drivers/video/fbdev/hyperv_fb.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c > index 4dc9077..a7e6eea 100644 > --- a/drivers/video/fbdev/hyperv_fb.c > +++ b/drivers/video/fbdev/hyperv_fb.c > @@ -308,7 +308,7 @@ static inline int synthvid_send(struct hv_device *hdev, > VM_PKT_DATA_INBAND, 0); > > > if (ret) > - pr_err("Unable to send packet via vmbus\n"); > + pr_err_ratelimited("Unable to send packet via vmbus; error %d\n", ret); > > > return ret; > }
From: Joe Perches <joe@perches.com> Sent: Tuesday, April 20, 2021 12:59 PM > > On Tue, 2021-04-20 at 08:44 -0700, Michael Kelley wrote: > > Due to a full ring buffer, the driver may be unable to send updates to > > the Hyper-V host. But outputing the error message can make the problem > > worse because console output is also typically written to the frame > > buffer. As a result, in some circumstances the error message is output > > continuously. > > > > Break the cycle by rate limiting the error message. Also output > > the error code for additional diagnosability. > > > > Signed-off-by: Michael Kelley <mikelley@microsoft.com> > > None of the callers of this function ever check the return status. > Why is important/useful to emit this message at all? > Except during device initialization, the messages tell Hyper-V about updates to the frame buffer contents. The fbdev framework functions (such as fillrect) that eventually call synthvid_send() are void functions. So the message is the only alert that something has gone wrong in the communication with Hyper-V, which makes it useful for diagnostic purposes. Michael > > --- > > drivers/video/fbdev/hyperv_fb.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c > > index 4dc9077..a7e6eea 100644 > > --- a/drivers/video/fbdev/hyperv_fb.c > > +++ b/drivers/video/fbdev/hyperv_fb.c > > @@ -308,7 +308,7 @@ static inline int synthvid_send(struct hv_device *hdev, > > VM_PKT_DATA_INBAND, 0); > > > > > > if (ret) > > - pr_err("Unable to send packet via vmbus\n"); > > + pr_err_ratelimited("Unable to send packet via vmbus; error %d\n", ret); > > > > > > return ret; > > } >
diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c index 4dc9077..a7e6eea 100644 --- a/drivers/video/fbdev/hyperv_fb.c +++ b/drivers/video/fbdev/hyperv_fb.c @@ -308,7 +308,7 @@ static inline int synthvid_send(struct hv_device *hdev, VM_PKT_DATA_INBAND, 0); if (ret) - pr_err("Unable to send packet via vmbus\n"); + pr_err_ratelimited("Unable to send packet via vmbus; error %d\n", ret); return ret; }
Due to a full ring buffer, the driver may be unable to send updates to the Hyper-V host. But outputing the error message can make the problem worse because console output is also typically written to the frame buffer. As a result, in some circumstances the error message is output continuously. Break the cycle by rate limiting the error message. Also output the error code for additional diagnosability. Signed-off-by: Michael Kelley <mikelley@microsoft.com> --- drivers/video/fbdev/hyperv_fb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)