Block profiler signals (SIGUSR2/SIGPROF) before starting Tokio runtime#107
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Block profiler signals (SIGUSR2/SIGPROF) before starting Tokio runtime#107robertbuessow wants to merge 1 commit into
robertbuessow wants to merge 1 commit into
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Block SIGUSR2/SIGPROF on the calling thread before starting the Tokio runtime so worker threads inherit a mask that excludes Julia profiler signals, preventing UB hangs when Profile.@Profile is active. Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
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Summary
Julia's CPU profiler delivers
SIGUSR2to every adopted Julia thread to collect backtraces. Tokio worker threads become adopted Julia threads via the@ccallablepreamble innotify_result_iceberg, but while they execute Rust code between Julia callbacks their Julia task context is incomplete. ReceivingSIGUSR2in that state causes UB in Julia's signal handler, manifesting as a hang whenProfile.@profileis active.Fix: call
pthread_sigmask(SIG_BLOCK, {SIGUSR2, SIGPROF}, &old)on the calling thread immediately beforeiceberg_init_runtime. Tokio worker threads inherit the mask and are never targeted by the profiler. The original mask is restored on the calling thread viafinallyafterinit_runtimereturns.@static if Sys.islinux()); the helpers are no-ops on other platforms.SIGPROF(used by older Julia / macOS profilers).Test plan
make testpassesProfile.@profileover an active scan no longer hangs🤖 Generated with Claude Code