Messages in this thread | | | Subject | Re: [PATCH v3 5/6] sched/deadline/rtmutex: Fix unprotected PI access in enqueue_task_dl() | From | Xunlei Pang <> | Date | Wed, 20 Apr 2016 21:00:32 +0800 |
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On 2016/04/20/ at 20:25, Peter Zijlstra wrote: > On Fri, Apr 15, 2016 at 10:19:12AM +0800, Xunlei Pang wrote: >> On 2016/04/15 at 09:58, Xunlei Pang wrote: >>> On 2016/04/14 at 23:31, Peter Zijlstra wrote: >>>> On Thu, Apr 14, 2016 at 07:37:06PM +0800, Xunlei Pang wrote: >>>>> We access @pi_task's data without any lock in enqueue_task_dl(), though >>>>> checked "dl_prio(pi_task->normal_prio)" condition, that's not enough. >>>> The proper fix is to ensure that pi_task is guaranteed to be blocked. >>> Even if pi_task was blocked, its parameters are still allowed to be changed, >>> so we have to do that. Did I miss something? >>> >>> Regards, >>> Xunlei >> Fortunately, I just reproduced through an overnight test, so it really happened in reality as I thought. > But what happens? How is it changed when it is blocked?
The top waiter's policy can be changed by other tasks through sched_setattr() syscall during it was blocked. I created another thread doing the following thing: while (1) { change the waiter to cfs do something change the waiter to deadline }
Regards, Xunlei
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