[Feature] Break up long walk of wait queue during wake up

[Alice Liu]

Description

In Fujitsu's acceptance test of 8 socket SKX systems, they found that NMI watchdog timer got triggered in wake_up_page_bit function. The cause is the long hold time of the wait queue lock to do the wake ups and traversal of the wait queue. (see LCK-4265)

We created a patch series to break up the long traversal of the wait queue in wake_up_page_bit. We bookmark the position in the wait queue after reaching a threshold of wake ups, and release the wait queue lock to allow other tasks blocked a chance to run (e.g. async wake up to remove itself from wake queue in finish_wait). Then we resume from the bookmarked location. This fixes the long spin lock hold time which triggered the watchdog timer.

Target Kernel: 4.14
Target Release: 18.04

[Alice Liu (dxliu)]

Merged in kernel v4.14-rc1.
These are commit ids:
11a19c7b099f96d00a8dec52bfbb8475e89b6745
2554db916586b228ce93e6f74a12fd7fe430a004

[Leann Ogasawara (leannogasawara)]

4.15 is now available in Bionic. Marking this Fix Released.