On Fri, Mar 04, 2022 at 01:29:31PM -0300, Marcelo Tosatti wrote:
>
> On systems that run FIFO:1 applications that busy loop
> on isolated CPUs, executing tasks on such CPUs under
> lower priority is undesired (since that will either
> hang the system, or cause longer interruption to the
> FIFO task due to execution of lower priority task
> with very small sched slices).
>
> Commit d479960e44f27e0e52ba31b21740b703c538027c ("mm: disable LRU
> pagevec during the migration temporarily") relies on
> queueing work items on all online CPUs to ensure visibility
> of lru_disable_count.
>
> However, its possible to use synchronize_rcu which will provide the same
> guarantees (see comment this patch modifies on lru_cache_disable).
>
> Fixes:
>
> [ 1873.243925] INFO: task kworker/u160:0:9 blocked for more than 622 seconds.
> [ 1873.243927] Tainted: G I --------- --- 5.14.0-31.rt21.31.el9.x86_64 #1
> [ 1873.243929] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 1873.243929] task:kworker/u160:0 state:D stack: 0 pid: 9 ppid: 2 flags:0x00004000
> [ 1873.243932] Workqueue: cpuset_migrate_mm cpuset_migrate_mm_workfn
> [ 1873.243936] Call Trace:
> [ 1873.243938] __schedule+0x21b/0x5b0
> [ 1873.243941] schedule+0x43/0xe0
> [ 1873.243943] schedule_timeout+0x14d/0x190
> [ 1873.243946] ? resched_curr+0x20/0xe0
> [ 1873.243953] ? __prepare_to_swait+0x4b/0x70
> [ 1873.243958] wait_for_completion+0x84/0xe0
> [ 1873.243962] __flush_work.isra.0+0x146/0x200
> [ 1873.243966] ? flush_workqueue_prep_pwqs+0x130/0x130
> [ 1873.243971] __lru_add_drain_all+0x158/0x1f0
> [ 1873.243978] do_migrate_pages+0x3d/0x2d0
> [ 1873.243985] ? pick_next_task_fair+0x39/0x3b0
> [ 1873.243989] ? put_prev_task_fair+0x1e/0x30
> [ 1873.243992] ? pick_next_task+0xb30/0xbd0
> [ 1873.243995] ? __tick_nohz_task_switch+0x1e/0x70
> [ 1873.244000] ? raw_spin_rq_unlock+0x18/0x60
> [ 1873.244002] ? finish_task_switch.isra.0+0xc1/0x2d0
> [ 1873.244005] ? __switch_to+0x12f/0x510
> [ 1873.244013] cpuset_migrate_mm_workfn+0x22/0x40
> [ 1873.244016] process_one_work+0x1e0/0x410
> [ 1873.244019] worker_thread+0x50/0x3b0
> [ 1873.244022] ? process_one_work+0x410/0x410
> [ 1873.244024] kthread+0x173/0x190
> [ 1873.244027] ? set_kthread_struct+0x40/0x40
> [ 1873.244031] ret_from_fork+0x1f/0x30
>
> Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Looks like great to me.
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
While I reviewed it, it seems I found a bug that br_lru_install
needs to check lru_cache_disabled under bh_lru_lock. Let me
cook the patch.
Thanks!
