On 09/28/2018 06:10 PM, Steve Muckle wrote:
On 09/27/2018 05:43 PM, Wanpeng Li wrote:
On your CPU4:
scheduler_ipi()
-> sched_ttwu_pending()
-> ttwu_do_activate() => p->sched_remote_wakeup should be
false, so ENQUEUE_WAKEUP is set, ENQUEUE_MIGRATED is not
-> ttwu_activate()
-> activate_task()
-> enqueue_task()
-> enqueue_task_fair()
-> enqueue_entity()
bool renorm = !(flags &
ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATE)
so renorm is false in enqueue_entity(), why you mentioned that the
cfs_rq->min_vruntime is still added to the se->vruntime in
enqueue_task_fair()?
Maybe this is a misunderstanding on my side but didn't you asked me to
'... Could you point out when the fair rq's min_vruntime is added to the
task's vruntime in your *later* scenario? ...'
Yeah, if the calltrace above and my analysis is correct, then the fair
rq's min_vruntime will not be added to the task's vruntime in your
*later* scenario, which means that your patch is not necessary.
In the scenario I observed, the task is not waking - it is running and
being deboosted from priority inheritance, transitioning from RT to CFS.
Dietmar and I both were able to reproduce the issue with the testcase I
posted earlier in this thread.
Correct, and with the same testcase I got this call stack in this scenario:
[ 35.588509] CPU: 1 PID: 2926 Comm: fair_task Not tainted
4.18.0-rc6-00052-g11b7dafa2edb-dirty #5
[ 35.597217] Hardware name: ARM Juno development board (r0) (DT)
[ 35.603080] Call trace:
[ 35.605509] dump_backtrace+0x0/0x168
[ 35.609138] show_stack+0x24/0x30
[ 35.612424] dump_stack+0xac/0xe4
[ 35.615710] enqueue_task_fair+0xae0/0x11c0
[ 35.619854] rt_mutex_setprio+0x5a0/0x628
[ 35.623827] mark_wakeup_next_waiter+0x7c/0xc8
[ 35.628228] __rt_mutex_futex_unlock+0x30/0x50
[ 35.632630] do_futex+0x74c/0xb28
[ 35.635912] sys_futex+0x118/0x198
[ 35.639280] el0_svc_naked+0x30/0x34
[...]
