On Fri, May 08, 2020 at 10:50:02AM +0200, Peter Zijlstra wrote: > On Thu, May 07, 2020 at 02:17:58PM -0400, Mathieu Desnoyers wrote: > > ----- On May 7, 2020, at 2:04 PM, Andy Lutomirski [email protected] wrote: > > > > > On Tue, May 5, 2020 at 7:14 AM Thomas Gleixner <[email protected]> wrote: > > >> > > >> From: Peter Zijlstra <[email protected]> > > >> > > >> A few exceptions (like #DB and #BP) can happen at any location in the > > >> code, > > >> this then means that tracers should treat events from these exceptions as > > >> NMI-like. The interrupted context could be holding locks with interrupts > > >> disabled for instance. > > >> > > >> Similarly, #MC is an actual NMI-like exception. > > > > > > Is it permissible to send a signal from inside nmi_enter()? I imagine > > > so, but I just want to make sure. > > > > If you mean sending a proper signal, I would guess not. > > > > I suspect you'll rather want to use "irq_work()" from NMI context to ensure > > the rest of the work (e.g. sending a signal or a wakeup) is performed from > > IRQ context very soon after the NMI, rather than from NMI context. > > > > AFAIK this is how this is done today by perf, ftrace, ebpf, and lttng. > > What Mathieu says. But I suspect you want to keep reading until > part4-18. That should get you what you really want.
LALALALA At least give a spoiler alert for those of us still enjoying part 1! -- Josh
