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

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@redhat.com>