Hi
I am currently using 4.14.6-rt7 on an De0-Nano-Soc (intel/altera arm v7 dual core)
board. I have added a small driver which adds some functionality like iio. As soon
as i have some realtime load on one core i see messages like:
Showing busy workqueues and worker pools:
workqueue events_freezable: flags=0x4
pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=1/256
pending: mmc_rescan
workqueue events_power_efficient: flags=0x80
pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=2/256
pending: phy_state_machine, neigh_periodic_work
workqueue mm_percpu_wq: flags=0x8
pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256
pending: vmstat_update
BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 68s!
Showing busy workqueues and worker pools:
workqueue mm_percpu_wq: flags=0x8
pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256
pending: vmstat_update
BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 98s!
Showing busy workqueues and worker pools:
workqueue mm_percpu_wq: flags=0x8
pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256
pending: vmstat_update
In other occasions i have seen complete system lockups where the only message i get is:
INFO: task systemd:1 blocked for more than 120 seconds.
Tainted: G O 4.14.6-rt7 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
systemd D 0 1 0 0x00001000
[<80793c70>] (__schedule) from [<80793f30>] (schedule+0x64/0xfc)
[<80793f30>] (schedule) from [<80796940>] (__write_rt_lock+0x13c/0x214)
[<80796940>] (__write_rt_lock) from [<80798464>] (rt_write_lock+0x24/0x28)
[<80798464>] (rt_write_lock) from [<8011f4b4>] (copy_process.part.5+0xfc4/0x17d8)
[<8011f4b4>] (copy_process.part.5) from [<8011fe58>] (_do_fork+0xc8/0x474)
[<8011fe58>] (_do_fork) from [<80120320>] (SyS_clone+0x30/0x38)
[<80120320>] (SyS_clone) from [<80107e60>] (ret_fast_syscall+0x0/0x28)
INFO: task systemd:1 blocked for more than 120 seconds.
I know that i am really using up all realtime budget on this system for one core
but i would expect that rt-throttling kicks in and gets some time for these
starving processes?
Best regards
Tim
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