On Fri, Jun 22, 2018 at 02:32:47PM -0400, Steven Rostedt wrote: > On Fri, 22 Jun 2018 11:19:16 -0700 > Joel Fernandes <j...@joelfernandes.org> wrote: > > > Sure. So in a later thread you mentioned "usermode helpers". I took a closer > > look at that subsystem, and it seems you can execute usermode helpers from > > atomic sections with help of UMH_NO_WAIT flag. > > > > Then I checked where this flag is used and it turns out its from the > > mce_work_trigger function in x86/kernel/cpu/mcheck/dev-mcelog.c which can be > > called infact from an interrupt context (mce_notify_irq). > > > > Is this the usecase you remember causing this weird transitions to > > userspace? > > But this case still looks like it uses work queues, it just doesn't > wait for the result. > > I'll have to look at the code from what it looked like back in 2011, to > see if there was an actual issue here back then.
There was. Been there, got the failure on real hardware. ;-) Thanx, Paul