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. > 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. -- Steve
