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xen-devel
[Xen-devel] Re: [RFC PATCH 27/33] Add the Xen virtual console driver.
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To: |
Arjan van de Ven <arjan@xxxxxxxxxxxxx> |
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Subject: |
[Xen-devel] Re: [RFC PATCH 27/33] Add the Xen virtual console driver. |
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From: |
Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> |
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Date: |
Tue, 18 Jul 2006 11:31:42 +0100 |
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Cc: |
Andrew Morton <akpm@xxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Ian Pratt <ian.pratt@xxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Chris Wright <chrisw@xxxxxxxxxxxx>, virtualization@xxxxxxxxxxxxxx |
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Tue, 18 Jul 2006 03:32:19 -0700 |
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On 18 Jul 2006, at 11:24, Arjan van de Ven wrote:
hmm somehow I find this code scary; we had similar code recently
elsewhere where this turned out to be a real issue; you now sleep for
"1" time, so you sleep for a fixed time if you aren't getting wakeups,
but if you are getting wakeups your code is upside down, I would expect
it to look like
+ set_current_state(TASK_INTERRUPTIBLE);
+ while (DRV(tty->driver)->chars_in_buffer(tty))
+ schedule_timeout(1);
+ if (signal_pending(current))
+ break;
+ if (timeout && time_after(jiffies, orig_jiffies + timeout))
+ break;
+ set_current_state(TASK_INTERRUPTIBLE);
+ }
instead, so that you don't have the wakeup race..
There's no wakeup signal, so no possibility of a wakeup race. That's
why we schedule_timeout() instead of wait_event() or similar. This code
is only used to flush the console when the kernel crashes, so we can
get the full oops, so waiting a little bit too long is acceptable.
Your suggested change is perhaps more idiomatic though, and less
jarring for reviewers. :-)
Thanks for your comments by the way. Reviewing lots of patches isn't
much fun.
-- Keir
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