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…ernel/debug/tracing. The default location for tracefs has been /sys/kernel/tracing since at least linux v4.1.
…uire elevated privileges if both /sys/kernel/tracing is readable and /proc/sys/kernel/perf_event_paranoid == -1
adamtassier
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Apr 16, 2025
src/recordhost.cpp
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| return stat(path, &buf) == 0 && ((buf.st_mode & 07777) & required) == required; | ||
| }; | ||
| static const auto paths = {"/sys/kernel/debug", "/sys/kernel/debug/tracing"}; | ||
| static const auto paths = {"/sys/kernel/", "/sys/kernel/tracing"}; |
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Checking /sys/kernel is probably redundant here right?
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I think so, yes - the old code was needed back then (Linux 3.x I think), because there tracing was mounted into debug, and thus needed to be checked separately
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that said, I wouldn't mind if we could rework this code:
check first if sys/kernel/tracing is usable, if so return early. otherwise keep backwards compat and check the two old locations?
milianw
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May 7, 2025
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milianw
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milianw
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ping? will you attend the review comment I gave you?
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milianw
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May 8, 2025
milianw
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May 8, 2025
milianw
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May 29, 2025
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Looks like a rebase may fix the failing checks, sounds like a good change to get in! |
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Hi,
This PR changes the file system location that is checked for
tracefs. At least since linux v4.1 the default location has been/sys/kernel/tracing/instead of/sys/kernel/debug/tracing/(but the latter was kept for compatability).I also changed the tooltip of the 'off-cpu profiling' checkbox to better reflect the conditions under which it can be checked as I had to go look into the source code.
This was an issue for me when setting up rootless 'off-cpu profiling' (ie not using 'elevate privileges'). Turns out the problem was that
/sys/kernel/debug/tracing/was not readable on my machine but/sys/kernel/tracing/was (viatracinggroup).