From: Keir Fraser <keir.xen@gmail.com>
To: Santosh Jodh <Santosh.Jodh@citrix.com>,
Sander Eikelenboom <linux@eikelenboom.it>
Cc: "wei.wang2@amd.com" <wei.wang2@amd.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: Using debug-key 'o: Dump IOMMU p2m table, locks up machine
Date: Sun, 02 Sep 2012 08:13:21 +0100 [thread overview]
Message-ID: <CC68C5A1.3D97A%keir.xen@gmail.com> (raw)
In-Reply-To: <7914B38A4445B34AA16EB9F1352942F1012F0F6F4BA7@SJCPMAILBOX01.citrite.net>
On 02/09/2012 03:08, "Santosh Jodh" <Santosh.Jodh@citrix.com> wrote:
>>>> It might schedule softirqs but that won't include scheduling or
>>>> running any guest vcpus. The vcpu that happens to be running on that
>>>> cpu at the time the debug dump starts, will be stuck unrunnable until the
>> dump completes.
>>>
>>> Why does'nt that vCPU get scheduled on some other pCPU? Is there a
>>> way to yield the CPU from the key handler?
>>
>> It can't be descheduled from this pCPU without running through the
>> scheduler. You could try running the handler in a tasklet -- a tasklet causes
>> other vCPUs to be descheduled from that pCPU, before it starts running.
>>
>> So you'd register a keyhandler which does a tasklet_schedule(), and do your
>> logging work in the tasklet handler.
>>
>> Worth a shot maybe?
>
> Yes - certainly. Is there a reason why all key handlers should not be
> tasklets?
Some keys you want to print immediately (stack trace), or you are using them
when the system is in a bad way, and deferring the tracing may cause you to
get no tracing at all. There may be a few informational keys, for irqs and
the like, that could be moved to tasklet context though, yes. It's just the
tasklet-in-hypervisor-thread mechanism is newer than the key handlers. ;-)
-- Keir
next prev parent reply other threads:[~2012-09-02 7:13 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-31 21:45 Using debug-key 'o: Dump IOMMU p2m table, locks up machine Sander Eikelenboom
2012-08-31 22:24 ` Santosh Jodh
2012-08-31 22:42 ` Sander Eikelenboom
2012-08-31 22:57 ` Santosh Jodh
2012-08-31 23:16 ` Sander Eikelenboom
2012-08-31 23:58 ` Santosh Jodh
2012-09-01 0:42 ` Santosh Jodh
2012-09-03 8:14 ` Jan Beulich
2012-09-01 2:01 ` Keir Fraser
2012-09-01 17:03 ` Santosh Jodh
2012-09-01 19:13 ` Keir Fraser
2012-09-02 2:08 ` Santosh Jodh
2012-09-02 7:13 ` Keir Fraser [this message]
2012-09-02 7:19 ` Keir Fraser
2012-09-02 8:43 ` Sander Eikelenboom
2012-09-02 14:58 ` Keir Fraser
2012-09-02 15:14 ` Sander Eikelenboom
2012-09-03 15:20 ` Wei Wang
2012-09-04 8:21 ` Sander Eikelenboom
2012-09-04 16:43 ` Sander Eikelenboom
2012-09-05 10:14 ` Jan Beulich
2012-09-05 10:25 ` Sander Eikelenboom
2012-09-05 10:40 ` Jan Beulich
2012-09-05 10:48 ` Sander Eikelenboom
2012-09-05 11:41 ` Jan Beulich
2012-09-05 12:11 ` Sander Eikelenboom
2012-09-05 14:15 ` Wei Wang
2012-09-05 15:05 ` Jan Beulich
2012-09-05 12:48 ` Wei Wang
2012-09-05 12:30 ` Wei Wang
2012-09-03 8:21 ` Jan Beulich
2012-09-03 8:33 ` Sander Eikelenboom
2012-09-03 9:05 ` Jan Beulich
2012-09-04 7:08 ` Sander Eikelenboom
2012-09-04 7:46 ` Jan Beulich
2012-09-04 8:13 ` Sander Eikelenboom
2012-09-04 9:26 ` Jan Beulich
2012-10-02 20:09 ` Konrad Rzeszutek Wilk
2012-10-03 13:12 ` Jan Beulich
2012-10-02 20:54 ` Matt Wilson
2012-09-20 8:08 ` Jan Beulich
2012-09-28 14:08 ` Sander Eikelenboom
2012-09-28 21:26 ` Jeremy Fitzhardinge
2012-10-02 20:08 ` Konrad Rzeszutek Wilk
2012-09-02 7:42 ` Keir Fraser
2012-09-04 6:35 ` Jan Beulich
2012-09-04 6:52 ` Sander Eikelenboom
2012-09-04 7:01 ` Keir Fraser
2012-09-04 6:59 ` Keir Fraser
2012-09-04 7:55 ` Jan Beulich
2012-09-04 8:04 ` Keir Fraser
2012-09-04 8:11 ` Keir Fraser
2012-09-04 8:20 ` Sander Eikelenboom
2012-09-04 8:38 ` Jan Beulich
2012-09-04 8:54 ` Keir Fraser
2012-09-04 9:40 ` Jan Beulich
2012-09-04 13:29 ` Andrew Cooper
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CC68C5A1.3D97A%keir.xen@gmail.com \
--to=keir.xen@gmail.com \
--cc=Santosh.Jodh@citrix.com \
--cc=linux@eikelenboom.it \
--cc=wei.wang2@amd.com \
--cc=xen-devel@lists.xen.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).