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Message-ID: <CALCETrXX0NV-=1f5ZU=R665h3M2unPgvtTKdgdhspev+LPHMXw@mail.gmail.com> Date: Thu, 5 Nov 2015 23:24:22 -0800 From: Andy Lutomirski <luto@...capital.net> To: Steven Rostedt <rostedt@...dmis.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org> Subject: What's TRACE_IRQS_OFF_DEBUG for? The comment says: /* * When dynamic function tracer is enabled it will add a breakpoint * to all locations that it is about to modify, sync CPUs, update * all the code, sync CPUs, then remove the breakpoints. In this time * if lockdep is enabled, it might jump back into the debug handler * outside the updating of the IST protection. (TRACE_IRQS_ON/OFF). * * We need to change the IDT table before calling TRACE_IRQS_ON/OFF to * make sure the stack pointer does not get reset back to the top * of the debug stack, and instead just reuses the current stack. */ #if defined(CONFIG_DYNAMIC_FTRACE) && defined(CONFIG_TRACE_IRQFLAGS) .macro TRACE_IRQS_OFF_DEBUG ... Unless I'm missing something, TRACE_IRQS_OFF isn't a tracepoint at all, though -- it's a lockdep debugging thing. Is the worry that someone might stick a kprobe or similar in the trace_hardirqs_off code? If so, could we just disable that instead? I could easily be missing something here. --Andy -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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