Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 29 Sep 2022 16:28:53 +0000
From:   Wei Liu <wei.liu@kernel.org>
To:     Saurabh Singh Sengar <ssengar@linux.microsoft.com>
Cc:     Thomas Zimmermann <tzimmermann@suse.de>, ssengar@microsoft.com,
        drawat.floss@gmail.com, airlied@linux.ie, daniel@ffwll.ch,
        linux-hyperv@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org, mikelley@microsoft.com,
        Wei Liu <wei.liu@kernel.org>
Subject: Re: [PATCH] drm/hyperv: Add ratelimit on error message
Message-ID: <YzXHxf/5WaiIrqMi@liuwe-devbox-debian-v2>
References: <1662736193-31379-1-git-send-email-ssengar@linux.microsoft.com>
 <88fab56a-f6e5-bae0-5ed7-1e01c070d136@suse.de>
 <20220911161142.GA7754@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220911161142.GA7754@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
Precedence: bulk

On Sun, Sep 11, 2022 at 09:11:42AM -0700, Saurabh Singh Sengar wrote:
> On Sat, Sep 10, 2022 at 08:06:05PM +0200, Thomas Zimmermann wrote:
> > Hi
> > 
> > Am 09.09.22 um 17:09 schrieb Saurabh Sengar:
> > >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.
> > >Rate limiting the error message, also output the error code for additional
> > >diagnosability.
> > >
> > >Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
> > >---
> > >  drivers/gpu/drm/hyperv/hyperv_drm_proto.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > >diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > >index 76a182a..013a782 100644
> > >--- a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > >+++ b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > >@@ -208,7 +208,7 @@ static inline int hyperv_sendpacket(struct hv_device *hdev, struct synthvid_msg
> > >  			       VM_PKT_DATA_INBAND, 0);
> > >  	if (ret)
> > >-		drm_err(&hv->dev, "Unable to send packet via vmbus\n");
> > >+		drm_err_ratelimited(&hv->dev, "Unable to send packet via vmbus; error %d\n", ret);
> > 
> > I better option would probably be drm_err_once(). Then you'd get the
> > first error message and skip all others.
> 
> Thanks for your comment however the intention here is to limit the printk messages and break the chain
> rather then printing only once. There can be cases where at different point of time we again get a
> ring buffer full condition and we don't want to miss that. We should get the message for each of these
> errror which are widely-separated in time not just the first time.

Applied to hyperv-next. Thanks.