Re: schedule_delayed_work with a 0 jiffy delay

2014-09-28 Thread Tejun Heo
Hello, Joe. On Sun, Sep 28, 2014 at 12:39:34PM -0400, Joe Lawrence wrote: > On Sun, 28 Sep 2014, Tejun Heo wrote: > > Hello, Joe. > > > > On Fri, Sep 26, 2014 at 10:52:27AM -0400, Joe Lawrence wrote: > > ... > > > I was wondering if such behavior was expected on !PREEMPT kernels, > > >

Re: schedule_delayed_work with a 0 jiffy delay

2014-09-28 Thread Joe Lawrence
On Sun, 28 Sep 2014, Tejun Heo wrote: > Hello, Joe. > > On Fri, Sep 26, 2014 at 10:52:27AM -0400, Joe Lawrence wrote: > ... > > I was wondering if such behavior was expected on !PREEMPT kernels, > > especially after b22ce2785d97 "workqueue: cond_resched() after > > processing each work item".

Re: schedule_delayed_work with a 0 jiffy delay

2014-09-28 Thread Tejun Heo
Hello, Joe. On Fri, Sep 26, 2014 at 10:52:27AM -0400, Joe Lawrence wrote: ... > I was wondering if such behavior was expected on !PREEMPT kernels, > especially after b22ce2785d97 "workqueue: cond_resched() after > processing each work item". In the ftraces I've observed from the RCU > stall,

Re: schedule_delayed_work with a 0 jiffy delay

2014-09-28 Thread Tejun Heo
Hello, Joe. On Fri, Sep 26, 2014 at 10:52:27AM -0400, Joe Lawrence wrote: ... I was wondering if such behavior was expected on !PREEMPT kernels, especially after b22ce2785d97 workqueue: cond_resched() after processing each work item. In the ftraces I've observed from the RCU stall,

Re: schedule_delayed_work with a 0 jiffy delay

2014-09-28 Thread Joe Lawrence
On Sun, 28 Sep 2014, Tejun Heo wrote: Hello, Joe. On Fri, Sep 26, 2014 at 10:52:27AM -0400, Joe Lawrence wrote: ... I was wondering if such behavior was expected on !PREEMPT kernels, especially after b22ce2785d97 workqueue: cond_resched() after processing each work item. In the

Re: schedule_delayed_work with a 0 jiffy delay

2014-09-28 Thread Tejun Heo
Hello, Joe. On Sun, Sep 28, 2014 at 12:39:34PM -0400, Joe Lawrence wrote: On Sun, 28 Sep 2014, Tejun Heo wrote: Hello, Joe. On Fri, Sep 26, 2014 at 10:52:27AM -0400, Joe Lawrence wrote: ... I was wondering if such behavior was expected on !PREEMPT kernels, especially after

schedule_delayed_work with a 0 jiffy delay

2014-09-26 Thread Joe Lawrence
Hello Tejun, (RHEL7 kernel, see config below) I'm debugging an RCU stall where it seems that the culprit is a kworker workqueue function that decides to reschedule itself over and over via schedule_delayed_work with a 0 jiffy delay. If I watch rcudata, I can see that the CPU currently running

schedule_delayed_work with a 0 jiffy delay

2014-09-26 Thread Joe Lawrence
Hello Tejun, (RHEL7 kernel, see config below) I'm debugging an RCU stall where it seems that the culprit is a kworker workqueue function that decides to reschedule itself over and over via schedule_delayed_work with a 0 jiffy delay. If I watch rcudata, I can see that the CPU currently running