Re: [PATCH] mm/kmemleak: report RCU-tasks quiescent states during the scan

[Breno Leitao]

On Mon, Jul 27, 2026 at 06:04:37AM -0700, Breno Leitao wrote:
> I found 3 different cases on Meta fleet, where rcu task stalls show up:
> 
> 1) kmemleak -> This patch solves it
> 2) KVM / kcompactd
>   * Holdout: kcompactd0 (pid 1216), state:R, nvcsw frozen at
>      716336/716336 across three reports 10 min apart (stuck ≥20 min in
>      one compaction pass)
>   * This is coming from: migrate_pages ->
>     kvm_mmu_notifier_invalidate_range_start ->
> 	   tdp_mmu_next_root -> tdp_mmu_zap_leafs
> 
> 3) Nvidia driver
>   * stuck in nv_procfs_read_lock_params

I've found an additional one:

4) While shrinking in reclaim:

   INFO: rcu_tasks detected stalls on tasks:
	0000000088620d09: .. nvcsw: 6735/6735 holdout: 1 idle_cpu: -1/8
	task:GlobalCPUThread state:R  running task  pid:2552016 tgid:2524552
  Call Trace:
   shrink_lruvec
   mem_cgroup_iter
   shrink_node

I've proposing promoting cond_resched() to cond_resched_tasks_rcu_qs():
https://lore.kernel.org/all/20260810-rcu_task_shrink_lruvec-v1-1-4d9f7d5251cb@xxxxxxxxxx/