Hello, I've been trying to trace down a hang issue for ages now, can't seem to get to the root of the problem. I'm wondering if anyone else has seen anything similar or has any suggestions. I am testing on a bmips chip on kernel version 4.1.20. I don't see the problem on ARM, so I have a suspicion there might be an issue with the smp mips specific code, but I cannot put my finger on it. The hang occurs when stress testing suspend and resume. Everyone once in a while it hangs when going into suspend and I see the following. 1. CPU 0 brings down other CPUs for suspend and attempts to parks smp threads. It waits for each thread to be parked before moving on. kernel/power/suspend.c: disable_nonboot_cpus() kernel/cpu.c: _cpu_down() then smpboot_park_threads() 2. CPU X(nonboot cpu) parks all smpboot threads except the last one. Then it hangs here. Under further inspection I see the following... The thread that needs to be parked is never scheduled instead it is waiting in the wake_list within the cpu runqueue(The cpu that should be parking the thread). The CPU (with its wait_list populated) is staying in the idle task loop. It never schedules the next task in the wait_list. I've tried pulling in potential fixes from upstream, but everything i tried so far has failed to fix the hang. I am running out of ideas on how to debug this. So any pointers on how to get deeper into the issue would be much appreciated. Thanks! Justin .
