Re: [PATCH] rcutorture: Avoid problematic critical section nesting on RT

Scott Wood
2021-08-20T03:23:58Z

On Tue, 2021-08-17 at 16:40 +0200, Sebastian Andrzej Siewior wrote:
> [bigeasy: remove 'preempt_disable(); local_bh_disable(); preempt_enable();
> local_bh_enable();' from the examples because this works on RT now. ]

Does it actually work? If preemption is disabled during local_bh_disable,
softirq_ctrl.lock won't be taken. If you then get preempted between the
preempt_enable() and the local_bh_enable(), and another task tries to do
local_bh_disable(), won't it successfully get softirq_ctrl.lock, add to
softirq_ctrl.cnt, and proceed right into the critical section?

Or am I missing something?

-Scott