linux-kernel - Re: [PATCH] habanalabs: print to kernel log when reset is finished

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Message-ID: <CAFCwf10FHK-qWbXcMF0mTCD+xTJkXaTzOjsZwpBwQNuc6T_QXA@mail.gmail.com>
Date:   Sun, 11 Aug 2019 10:40:21 +0300
From:   Oded Gabbay <oded.gabbay@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
        Omer Shpigelman <oshpigelman@...ana.ai>,
        Tomer Tayar <ttayar@...ana.ai>
Subject: Re: [PATCH] habanalabs: print to kernel log when reset is finished

On Sun, Aug 11, 2019 at 10:38 AM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Sat, Aug 10, 2019 at 08:45:54PM +0300, Oded Gabbay wrote:
> > On Sat, Aug 10, 2019 at 8:23 PM Greg KH <gregkh@...uxfoundation.org> wrote:
> > >
> > > On Sat, Aug 10, 2019 at 06:29:16PM +0300, Oded Gabbay wrote:
> > > > On Sat, Aug 10, 2019 at 3:53 PM Greg KH <gregkh@...uxfoundation.org> wrote:
> > > > >
> > > > > On Sat, Aug 10, 2019 at 03:38:08PM +0300, Oded Gabbay wrote:
> > > > > > Now that we don't print the queue testing messages, we need to print when
> > > > > > the reset is finished so whoever looks at the kernel log will know the
> > > > > > reset process was finished successfully and the driver is not stuck.
> > > > > >
> > > > > > Signed-off-by: Oded Gabbay <oded.gabbay@...il.com>
> > > > > > ---
> > > > > >  drivers/misc/habanalabs/device.c | 2 ++
> > > > > >  1 file changed, 2 insertions(+)
> > > > > >
> > > > > > diff --git a/drivers/misc/habanalabs/device.c b/drivers/misc/habanalabs/device.c
> > > > > > index 9a5926888b99..1fac808c2546 100644
> > > > > > --- a/drivers/misc/habanalabs/device.c
> > > > > > +++ b/drivers/misc/habanalabs/device.c
> > > > > > @@ -907,6 +907,8 @@ int hl_device_reset(struct hl_device *hdev, bool hard_reset,
> > > > > >       else
> > > > > >               hdev->soft_reset_cnt++;
> > > > > >
> > > > > > +     dev_info(hdev->dev, "Successfully finished resetting the device\n");
> > > > >
> > > > > Really?  For doing things "properly" there is no need to spam the kernel
> > > > > log.  Only spit stuff out if an error happens.
> > > > >
> > > > > thanks,
> > > > >
> > > > > greg k-h
> > > >
> > > > I beg to differ for two reasons:
> > > > 1. Reset happens very rarely, if at all. So this message (that get
> > > > printed after reset is done) will definitely not spam the kernel log.
> > > > 2. When a reset starts we print an appropriate error message. I think
> > > > it is expected by the user that we will also print if and when the
> > > > reset has finished successfully. I really believe that lack of this
> > > > printing might be deceiving for users.
> > >
> > > How is anyone going to parse the kernel log for anything to know if
> > > something happens?
> >
> > Actually our jenkins server parse the kernel log and look for bad
> > messages from the driver...
> > But the main reason for this, IMO, is for developers (in userspace)
> > that run with a terminal open on the kernel log to see if something
> > bad happens while they run their applications.
> >
> > >
> > > How do you trigger a reset?  Is it done by userspace?  If so, just
> > > notify them then.
> >
> > Reset can be triggered by two main reasons, but a userspace
> > application is *not* one of them.
> > It can be due to a command submission not finishing in time or from a
> > major error in the device (e.g. double ECC error).
> > That's why I think it is important to tell them the reset +
> > re-initialization flow was finished successfully.
> > Of course all this information, let's call it operational status, can
> > be acquired by the INFO IOCTL the driver provides, but it is *really*
> > convenient, IMHO, to see these type of messages in the kernel log
> > while they happen.
>
> Ah, yes, if this is something that userspace can not trigger then it's
> ok.  But you should then make it a 'dev_warn' to match up with the
> message level when the reset starts.
>
> thanks,
>
> greg k-h

Sure, np.
Thanks,
Oded