Messages in this thread | | | Date | Mon, 25 Sep 2023 15:10:20 -0600 | Subject | Re: [PATCH v1] arch/x86: port I/O tracing on x86 | From | Dan Raymond <> |
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Can I get more feedback on this please? I think I've addressed all of Peter Zijlstra's concerns:
1) cannot use early_console->write()
That is not true. Everything that includes boot.h (ie. 'arch/x86/boot/early_serial_console.c') will not change due to the '#ifdef BOOT_BOOT_H' guard. Also tracing will not be compiled in unless 'CONFIG_TRACEPOINTS' is true. Finally, tracing will be disabled at boot until the user mounts the tracefs and explicitly enables 'portio' events. When tracing is disabled the trace routines execute a nop instruction and return immediately.
2) tracing relies on RCU which might not be alive yet and might itself be the problem
RCU is not needed unless/until tracing is enabled. I also demonstrated that port I/O tracing works correctly during boot by testing this patch with "trace_event=portio" on the command line.
I plan to submit another patch due to the compiler warning reported by the "kernel test robot". Before I do that I would like to get more feedback so I can address any other concerns or suggestions.
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