On Thu, Aug 28, 2025 at 10:34 PM Steven Rostedt <[email protected]> wrote: > > On Thu, 28 Aug 2025 17:09:35 +0800 > Menglong Dong <[email protected]> wrote: > > > > [ 354.955971][ T4652] dump_stack_lvl+0x7c/0x90 > > > [ 354.955978][ T4652] lockdep_rcu_suspicious+0x14f/0x1c0 > > > [ 354.955987][ T4652] __rhashtable_lookup+0x1e0/0x260 > > > > rcu_read_lock() is not needed in fprobe_entry, but > > rcu_dereference_check() is used in rhltable_lookup(), which > > causes this warning. > > Why is rcu_read_lock() not needed in fprobe_entry()?
This is how it worked previously. In ftrace_test_recursion_trylock(), preemption will be disabled, which ensure the RCU read-side critical section. Thanks! Menglong Dong > > -- Steve > > > > > Adding rcu_read_lock() here is able to suppress this warning. > > Maybe we need only rcu_lock_acquire(&rcu_lock_map) here, > > but it's not a common usage. What do you think, Masami? >
