Remote draining of pages was removed from 5.6-rt. Unfortunately its necessary for use-cases which have a busy spinning SCHED_FIFO thread on isolated CPU: [ 7475.821066] INFO: task ld:274531 blocked for more than 600 seconds. [ 7475.822157] Not tainted 4.18.0-208.rt5.20.el8.x86_64 #1 [ 7475.823094] echo 0 /proc/sys/kernel/hung_task_timeout_secs disables this message. [ 7475.824392] ld D 0 274531 274530 0x00084080 [ 7475.825307] Call Trace: [ 7475.825761] __schedule+0x342/0x850 [ 7475.826377] schedule+0x39/0xd0 [ 7475.826923] schedule_timeout+0x20e/0x410 [ 7475.827610] ? __schedule+0x34a/0x850 [ 7475.828247] ? ___preempt_schedule+0x16/0x18 [ 7475.828953] wait_for_completion+0x85/0xe0 [ 7475.829653] flush_work+0x11a/0x1c0 [ 7475.830313] ? flush_workqueue_prep_pwqs+0x130/0x130 [ 7475.831148] drain_all_pages+0x140/0x190 [ 7475.831803] __alloc_pages_slowpath+0x3f8/0xe20 [ 7475.832571] ? mem_cgroup_commit_charge+0xcb/0x510 [ 7475.833371] __alloc_pages_nodemask+0x1ca/0x2b0 [ 7475.834134] pagecache_get_page+0xb5/0x2d0 [ 7475.834814] ? account_page_dirtied+0x11a/0x220 [ 7475.835579] grab_cache_page_write_begin+0x1f/0x40 [ 7475.836379] iomap_write_begin.constprop.44+0x1c1/0x370 [ 7475.837241] ? iomap_write_end+0x91/0x290 [ 7475.837911] iomap_write_actor+0x92/0x170 See individual patches for details.
