flicker-free suspend/resume on Intel [LWN.net]

flicker-free suspend/resume on Intel

Posted Mar 8, 2013 0:56 UTC (Fri) by mgedmin (subscriber, #34497)
In reply to: flicker-free suspend/resume on Intel by raven667
Parent article: The conclusion of the 3.9 merge window

Somewhat tangentially there's a very interesting article about DHCP tricks that MacOS X does to reconnect faster.

I'd love to see Network Manager pick up something from that.

Instead, currently when I suspend a laptop via ssh -t foo sudo pm-suspend, I get to enjoy a lapsed DHCP lease on resume, for a few hours. According to strace that's because dhcpd expiration timer (i.e. select() with a timeout) simply stops while the laptop is suspended. Connection still works, but the wifi router doesn't resolve the laptop's hostname until dhcpd finally wakes up.

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flicker-free suspend/resume on Intel

Posted Mar 8, 2013 9:07 UTC (Fri) by johill (subscriber, #25196) [Link]

This would be easier in connman as it has DHCP built into it rather than calling out to dhclient (running as a daemon)

flicker-free suspend/resume on Intel

Posted Mar 8, 2013 15:35 UTC (Fri) by njwhite (subscriber, #51848) [Link]

Ah, I've run into this with wpa_supplicant on Debian. Have you found a solution to it? Is there a straightforward way to get dhclient to wake up when the computer resumes?

flicker-free suspend/resume on Intel

Posted Mar 14, 2013 0:46 UTC (Thu) by kevinm (guest, #69913) [Link]

If CLOCK_MONOTONIC in Linux actually worked according to POSIX spec, then a timer based on this clock could be used to fix this problem.

(POSIX says that CLOCK_MONOTONIC measures time elapsed since "an unspecified point in the past", and further "This point does not change after system start-up time.". On Linux however, CLOCK_MONOTONIC stops while the system is suspended, which is clearly nonconforming).