This commit ensures that workqueue rescuer threads are affined to the
platform CPUs specified by the "kthread_cpus" kernel argument. Prior
to this commit, rescuer threads could be bound to any CPU. Rescuer
threads are described in "kernel/workqueue.c" as follows:
"Regular work processing on a pool may block trying to create a new
worker which uses GFP_KERNEL allocation which has slight chance of
developing into deadlock if some works currently on the same queue
need to be processed to satisfy the GFP_KERNEL allocation. This is
the problem rescuer solves.
When such condition is possible, the pool summons rescuers of all
workqueues which have works queued on the pool and let them process
those works so that forward progress can be guaranteed."
This commit also affines unbound workqueues to the platform CPUs instead
of the housekeeping CPUs, because the latter can be a superset of the
former.
Verification:
Compared the affinity of workqueue thread between before and after the
fix, the affinity was 0xff before this commit that mean the thread
could be bound to cpu0-7, the affinity was 0x3 after the fix with
"kthread_cpus=0, 1", which only could be bound to cpu0, 1. Also checked
unbound workqueue such as "writeback" whose affinity also was 0x3 with
"kthread_cpus=0, 1". We did not find the commit break anything else.
Closes-Bug: #1948639
Signed-off-by: M. Vefa Bicakci <vefa.bicakci@windriver.com>
Signed-off-by: Jiping Ma <jiping.ma2@windriver.com>
Change-Id: I8afd56c8d0d0526d523accf3ea45ee02635b1602
cfe452afa5