Re: [BUG] srcu: false-positive WARN in cleanup_srcu_struct() after 78a38cbf6f20

[Sunho Park <shpark061104@gmail.com>]

On 8/25/26 21:33, Zqiang wrote:
> 
> If srcu_barrier() be invoke before srcu_cleanup(), and after srcu_barrier()
> completion, there are no concurrent srcu grace period start again (e.g. call_srcu() calls),
> the timer_delete_sync() should return false, the rcu_segcblist_n_cbs()
> will not be check.
> 
> Or did I miss something?
In srcu_gp_end(), delayed work timer is always armed in SRCU_SIZE_SMALL 
mode regardless of whether its cblist has callbacks:

	if (ss_state < SRCU_SIZE_WAIT_BARRIER) {
		srcu_schedule_cbs_sdp(per_cpu_ptr(ssp->sda, get_boot_cpu_id()),
					cbdelay);
	} else {
		...
	}

and with cbdelay=1 (the non-expedited path) srcu_schedule_cbs_sdp() arms 
the per-CPU delay_work timer for the next jiffy. This includes the 
srcu_gp_end() whose grace period makes the barrier's callbacks ready, so 
an armed timer is left pending when srcu_invoke_callbacks() completes 
the barrier.

Thanks
Sunho Park