Re: [PATCH] uprobes: fix incorrect lockdep condition in filter_chain()

[Oleg Nesterov]

On 01/28, Breno Leitao wrote:
>
> The list_for_each_entry_rcu() in filter_chain() uses
> rcu_read_lock_trace_held() as the lockdep condition, but the function
> holds consumer_rwsem, not the RCU trace lock.
> 
> This gives me the following output when running with some locking debug
> option enabled:
> 
>   kernel/events/uprobes.c:1141 RCU-list traversed in non-reader section!!
>     filter_chain
>     register_for_each_vma
>     uprobe_unregister_nosync
>     __probe_event_disable
>
> Remove the incorrect lockdep condition since the rwsem provides
> sufficient protection for the list traversal.

I hope Andrii will recheck, but looks obviously correct to me.

> Fixes: 87195a1ee332a ("uprobes: switch to RCU Tasks Trace flavor for better performance")

This commit just change the __list_check_rcu() condition...

Perhaps
Fixes: cc01bd044e6a ("uprobes: travers uprobe's consumer list locklessly under SRCU protection")

makes more sense?

Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx>