On Tue, Sep 27, 2016 at 04:39:26PM +0200, Peter Zijlstra wrote: > On Tue, Sep 27, 2016 at 04:22:20PM +0200, Frederic Weisbecker wrote: > > > The RCU context tracking doesn't take care of callbacks. It's only there > > to tell the RCU core whether the CPU runs code that may or may not run > > RCU read side critical sections. This is assumed by "kernel may use RCU, > > userspace can't". > > Userspace never can use the kernels RCU in any case. What you mean to > say is that userspace is treated like an idle CPU in that the CPU will > no longer be part of the RCU quescent state machine. > > The transition to userspace (as per context tracking) must ensure that > CPUs RCU state is 'complete', just like our transition to idle (mostly) > does. Exactly! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>