On Thu, Jun 16, 2016 at 12:16:04AM +0200, Peter Zijlstra wrote: > On Wed, Jun 15, 2016 at 02:46:10PM -0700, Paul E. McKenney wrote: > > Currently, if the very first call to call_rcu_tasks() has irqs disabled, > > it will create the rcu_tasks_kthread with irqs disabled, which will > > result in a splat in the memory allocator, which kthread_run() invokes > > with the expectation that irqs are enabled. > > > > This commit fixes this problem by deferring kthread creation if called > > with irqs disabled. The first call to call_rcu_tasks() that has irqs > > enabled will create the kthread. > > > > This bug was detected by rcutorture changes that were motivated by > > Iftekhar Ahmed's mutation-testing efforts. > > Seems fragile. What if someone manages to only use call_rcu_tasks() with > IRQs disabled?
It would have to have users before that could possibly happen. :-/ And it would not be hard to remove the fragility if needed by setting up a workqueue, possibly mediated by a timer or whatever. But it is hard to motivate myself to do so in advance of users. For that matter... Steven, is call_rcu_tasks() needed, or should I just rip it out? Thanx, Paul