On Thu, 18 May 2017, Steven Rostedt wrote: > On Thu, 18 May 2017 15:48:55 +0200 (CEST) > Miroslav Benes <mbe...@suse.cz> wrote: > > > On Thu, 18 May 2017, Steven Rostedt wrote: > > > > > > > > From: "Steven Rostedt (VMware)" <rost...@goodmis.org> > > > > > > As stack tracing now requires "rcu watching", force RCU to be watching > > > when > > > recording a stack trace. > > > > > > Link: http://lkml.kernel.org/r/20170512172449.879684...@goodmis.org > > > > > > Cc: "Paul E. McKenney" <paul...@linux.vnet.ibm.com> > > > Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org> > > > --- > > > > > > Changes since v1: > > > > > > My testing discovered that the stack trace can be called with > > > interrupts enabled, which is a no no to have when calling > > > rcu_irq_enter(). When interrupts are enabled, as with being in an > > > NMI, RCU will also be watching. > > > > Would rcu_irq_enter_irqson() help then? This is what Petr used in a live > > patching handler. > > > > Yes, that could work too, but I wanted to avoid disabling interrupts if > we didn't have to.
Ok, that makes sense. > > Your solution works too, of course. Just asking if I am not missing > > something. > > > > Nope, I was just trying to keep the overhead down. As this can be > called by every event enabled, as well as functions being traced. I > figured that local_save_irqs() is faster than a pair of > local_irq_save()/ local_irq_restore() calls. (noticed Paul's reply)... yeah, it'd great. Damn, this is mindblowing. Thanks, Miroslav
