Re: [Xen-devel] [PATCH 1/1] xen/gnttab: print log at level XENLOG_ERR before panic

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.04.19 at 18:00, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 23/04/2019 12:47, George Dunlap wrote:
>> On 4/23/19 11:37 AM, Andrew Cooper wrote:
>>> On 22/04/2019 13:39, Dongli Zhang wrote:
>>>> Print log at level XENLOG_ERR (instead XENLOG_INFO) as domain_crash()
>>>> indicates there is fatal error.
>>>>
>>>> Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
>>>> ---
>>>>  xen/common/grant_table.c | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
>>>> index 80728ea..725c618 100644
>>>> --- a/xen/common/grant_table.c
>>>> +++ b/xen/common/grant_table.c
>>>> @@ -1282,7 +1282,7 @@ unmap_common(
>>>>      if ( unlikely((rd = rcu_lock_domain_by_id(dom)) == NULL) )
>>>>      {
>>>>          /* This can happen when a grant is implicitly unmapped. */
>>>> -        gdprintk(XENLOG_INFO, "Could not find domain %d\n", dom);
>>>> +        gdprintk(XENLOG_ERR, "Could not find domain %d\n", dom);
>>> While I agree with the change in principle, what does this actually do? 
>>> The entire printk() is compiled out in release builds, and debug builds
>>> log all messages.
>> ...by default; but presumably you can turn that down, right?
> 
> Yes you can, but a) noone does, because these are debug builds and b)
> that isn't the point.  If we care about this message being printed, it
> mustn’t be a gdprintk().
> 
> It either wants to turn into a gprintk() at XENLOG_INFO, or wants
> deleting entirely, but simply shuffling the exact level for a gdprintk()
> is tantamount to useless.

FWIW I agree, and I think there are quite a few more candidates of
debug messages that would better go away, and should probably
have been stripped off before the original commit introducing them.

The one reason not to drop the message here, but to switch to
gprintk(), is the adjacent domain_crash(). This, however, then is
a reason to give it a log level above INFO.

Jan


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