----- On May 7, 2020, at 2:04 PM, Andy Lutomirski l...@kernel.org wrote: > On Tue, May 5, 2020 at 7:14 AM Thomas Gleixner <t...@linutronix.de> wrote: >> >> From: Peter Zijlstra <pet...@infradead.org> >> >> 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. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
