Messages in this thread | | | Date | Thu, 7 May 2020 14:17:58 -0400 (EDT) | From | Mathieu Desnoyers <> | Subject | Re: [patch V4 part 1 35/36] x86: Replace ist_enter() with nmi_enter() |
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----- On May 7, 2020, at 2:04 PM, Andy Lutomirski luto@kernel.org wrote:
> On Tue, May 5, 2020 at 7:14 AM Thomas Gleixner <tglx@linutronix.de> wrote: >> >> From: Peter Zijlstra <peterz@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
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