scx_utils, scx_lavd: Harden the futex tracing. #2950
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added 2 commits
October 27, 2025 10:27
When the kernel does not enable the tracepoint, there is no 'available_events' under '/sys/kernel/debug/tracing'. So, let's return 'Ok(false)' in that case. Signed-off-by: Changwoo Min <[email protected]>
When the kernel is built without ftrace support, setting the autoload of futex functions using ftrace causes the verifier errors. So, let's check if the kernel supports ftrace before tracing the futex functions. Signed-off-by: Changwoo Min <[email protected]>
multics69
requested review from
EricccTaiwan,
arighi,
daidavid,
hodgesds and
htejun
|
Hey, Thanks for looking into it ! Can disabling FTRACE negatively affect performance, I.e. is it used for non-debugging purposes, e.g. tracing processes to get insights on better scheduling decisions ? |
It depends on workloads, of course. If the workload heavily relies on futex, it will help a bit. Otherwise, it shouldn't matter much. |
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When neither tracepoint nor ftrace is enabled by the kernel, the existing futex tracing code raises runtime errors. This PR is to handle such error cases gracefully. It first add a missing error condition check (compat::tracepoint_exists), and check if ftraced is available before attaching ftrace points (compat::tracer_available).
This should resolve the problem reported at Frogging-Family/linux-tkg#1156
Once this is merged, #2914 should be closed.