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Re: [Qemu-devel] chardev's and fd's in monitors
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-devel] chardev's and fd's in monitors |
Date: |
Wed, 19 Oct 2016 13:21:58 +0100 |
User-agent: |
Mutt/1.7.0 (2016-08-17) |
On Wed, Oct 19, 2016 at 02:16:05PM +0200, Markus Armbruster wrote:
> "Daniel P. Berrange" <address@hidden> writes:
>
> > On Wed, Oct 19, 2016 at 11:05:53AM +0100, Dr. David Alan Gilbert wrote:
> >>
> >> We need a way to be able to report an error without plumbing error_setg
> >> up the stack; if you're saying error_report isn't suitable then we
> >> should just recommend we switch everything in migration back to
> >> fprintf(stderr,
>
> In the cases where error_report() isn't suitable, fprintf() is just as
> unsuitable for the exact same reasons.
>
> > Well both error_report() + fprintf are broken from POV of anything
> > using QMP. error_report() is slightly less broken for HMP,
>
> error_report() is not broken at all for HMP code. The trouble is code
> that can't know whether it's running in a context where error_report()
> is suitable.
>
> > but doesn't
> > help QMP.
>
> Correct.
>
> > In the short term we should just make error_report be threadsafe in
> > its usage of the monitor.
>
> Any problems left once cur_mon is thread-local (which it should be
> anyway)?
If we make cur_mon a thread-local, then error_report() is equivalent
to fprintf(stderr) for the migration code, since the migration
code runs in a different thread thread, and so would always see
cur_mon == NULL.
> > Beyond the short term we have no choice but
> > to plumb in error_setg throughout, otherwise QMP will continue to
> > have useless error reporting in this area of code.
>
> Actually, no choice but propagate errors up the stack until they reach a
> spot that knows how to report them. error_setg() is *one* way to do
> that. Its prime advantage is ability to carry an error message. Its
> disadvantage is boilerplate. Use it as needed. Just don't convert back
> and forth between Error and other representations while propagating up
> the stack.
Regards,
Daniel
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- Re: [Qemu-devel] chardev's and fd's in monitors, (continued)
- Re: [Qemu-devel] chardev's and fd's in monitors, Markus Armbruster, 2016/10/19
- Re: [Qemu-devel] chardev's and fd's in monitors, Dr. David Alan Gilbert, 2016/10/19
- Re: [Qemu-devel] chardev's and fd's in monitors, Daniel P. Berrange, 2016/10/19
- Re: [Qemu-devel] chardev's and fd's in monitors, Markus Armbruster, 2016/10/19
- Re: [Qemu-devel] chardev's and fd's in monitors, Dr. David Alan Gilbert, 2016/10/19
- Re: [Qemu-devel] chardev's and fd's in monitors, Daniel P. Berrange, 2016/10/19
- Re: [Qemu-devel] chardev's and fd's in monitors, Markus Armbruster, 2016/10/19
- Re: [Qemu-devel] chardev's and fd's in monitors,
Daniel P. Berrange <=
- Re: [Qemu-devel] chardev's and fd's in monitors, Dr. David Alan Gilbert, 2016/10/19
- Re: [Qemu-devel] chardev's and fd's in monitors, Daniel P. Berrange, 2016/10/20
- Re: [Qemu-devel] chardev's and fd's in monitors, Marc-André Lureau, 2016/10/20
- Re: [Qemu-devel] chardev's and fd's in monitors, Markus Armbruster, 2016/10/20
- Re: [Qemu-devel] chardev's and fd's in monitors, Paolo Bonzini, 2016/10/20
- Re: [Qemu-devel] chardev's and fd's in monitors, Markus Armbruster, 2016/10/21
- Re: [Qemu-devel] chardev's and fd's in monitors, Paolo Bonzini, 2016/10/21
- Re: [Qemu-devel] chardev's and fd's in monitors, Markus Armbruster, 2016/10/24
- Re: [Qemu-devel] chardev's and fd's in monitors, Daniel P. Berrange, 2016/10/21
- Re: [Qemu-devel] chardev's and fd's in monitors, Dr. David Alan Gilbert, 2016/10/20