ruby: add skip_native_resume to avoid tail call exhaustion (upstream prep)#38
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ruby: add skip_native_resume to avoid tail call exhaustion (upstream prep)#38
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When the Ruby unwinder encounters a cfunc (C-implemented Ruby method), it normally transitions back to the native unwinder to unwind through the C code, then re-enters the Ruby unwinder when it detects the Ruby interpreter loop. Each such round-trip costs 2-3 tail calls out of a budget of 29, so a Ruby stack with 10+ cfuncs can easily truncate. This adds a skip_native_resume flag to RubyProcInfo that, when set, pushes cfunc frames inline without transitioning to the native unwinder. This trades native frames within cfuncs (e.g., the C call chain inside Array#sort) for complete Ruby-level traces without truncation. The flag is controlled by OTEL_EBPF_RUBY_SKIP_NATIVE_RESUME (default: false). Set to 'true' to enable.
- Correct inline comment that incorrectly stated 'Default to skipping' when the actual default is false (requires explicit opt-in) - Add note that skipNativeResume() is evaluated per-process at attach time
When skip_native_resume is true, the end-of-stack check should stop instead of resuming native unwinding. Without this, the native unwinder can re-enter the Ruby unwinder from JIT anonymous mappings, pushing frames in wrong positions.
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Rebased version of Shopify PR #31 for staging before upstream submission.
BPF blobs will need rebuilding.