Re: schdule bug in 4.4.38-rt49

["xiaoqiang.zhao" <zhaoxiaoqiang007@gmail.com>]

Resend as plain-text to linux-rt-users list.

在 2019/7/4 下午1:50, xiaoqiang.zhao 写道:

在 2019/7/3 下午7:42, Sebastian Andrzej Siewior 写道:
> On 2019-06-26 15:35:04 [+0800], xiaoqiang.zhao wrote:
>> Hi, guys:
> Hi,
>
Thanks for your reply ;-)

>> 2) -> __schedule_bug ( leads to kernel pagefault exception, OOPS!!)
>>
>> Before schedule, we have call preempt_disable twice, this will 
>> definitely
>> bump preempt_count to 2 and
>
> something probably disabled preemption before that

I feel this is not make sense.  In my opinion, the preempt_count must be 
zero before we call 'schedule()',

otherwise, in_atomic_preempt_off will return true and trigger the 
__schedule_bug. If we have already

disable_preempt, we may in atomic context and we should not call 
schedule, right ?

>> in_atomic_preempt_off will fail.
>>
>> I did not figure out:   WHY we call schedule inside 
>> rt_spin_lock_slowlock
>> and under what condition this call is correct ?
> if the lock is acquired you schedule out and wait und it is available
> again.
got this.


>