Global datarace #6
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adienes
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Sep 15, 2025
Use an atomic fetch and add to fix a data race in `Module()` identified by tsan: ``` ./usr/bin/julia -t4,0 --gcthreads=1 -e 'Threads.@threads for i=1:100 Module() end' ================== WARNING: ThreadSanitizer: data race (pid=5575) Write of size 4 at 0xffff9bf9bd28 by thread T9: #0 jl_new_module__ /home/user/c/julia/src/module.c:487:22 (libjulia-internal.so.1.13+0x897d4) #1 jl_new_module_ /home/user/c/julia/src/module.c:527:22 (libjulia-internal.so.1.13+0x897d4) #2 jl_f_new_module /home/user/c/julia/src/module.c:649:22 (libjulia-internal.so.1.13+0x8a968) #3 <null> <null> (0xffff76a21164) #4 <null> <null> (0xffff76a1f074) #5 <null> <null> (0xffff76a1f0c4) #6 _jl_invoke /home/user/c/julia/src/gf.c (libjulia-internal.so.1.13+0x5ea04) #7 ijl_apply_generic /home/user/c/julia/src/gf.c:3892:12 (libjulia-internal.so.1.13+0x5ea04) #8 jl_apply /home/user/c/julia/src/julia.h:2343:12 (libjulia-internal.so.1.13+0x9e4c4) #9 start_task /home/user/c/julia/src/task.c:1249:19 (libjulia-internal.so.1.13+0x9e4c4) Previous write of size 4 at 0xffff9bf9bd28 by thread T10: #0 jl_new_module__ /home/user/c/julia/src/module.c:487:22 (libjulia-internal.so.1.13+0x897d4) #1 jl_new_module_ /home/user/c/julia/src/module.c:527:22 (libjulia-internal.so.1.13+0x897d4) #2 jl_f_new_module /home/user/c/julia/src/module.c:649:22 (libjulia-internal.so.1.13+0x8a968) #3 <null> <null> (0xffff76a21164) #4 <null> <null> (0xffff76a1f074) #5 <null> <null> (0xffff76a1f0c4) #6 _jl_invoke /home/user/c/julia/src/gf.c (libjulia-internal.so.1.13+0x5ea04) #7 ijl_apply_generic /home/user/c/julia/src/gf.c:3892:12 (libjulia-internal.so.1.13+0x5ea04) #8 jl_apply /home/user/c/julia/src/julia.h:2343:12 (libjulia-internal.so.1.13+0x9e4c4) #9 start_task /home/user/c/julia/src/task.c:1249:19 (libjulia-internal.so.1.13+0x9e4c4) Location is global 'jl_new_module__.mcounter' of size 4 at 0xffff9bf9bd28 (libjulia-internal.so.1.13+0x3dbd28) ```
adienes
pushed a commit
that referenced
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Sep 15, 2025
Simplify `workqueue_for`. While not strictly necessary, the acquire load
in `getindex(once::OncePerThread{T,F}, tid::Integer)` makes
ThreadSanitizer happy. With the existing implementation, we get false
positives whenever a thread other than the one that originally allocated
the array reads it:
```
==================
WARNING: ThreadSanitizer: data race (pid=6819)
Atomic read of size 8 at 0xffff86bec058 by main thread:
#0 getproperty Base_compiler.jl:57 (sys.so+0x113b478)
#1 julia_pushNOT._1925 task.jl:868 (sys.so+0x113b478)
#2 julia_enq_work_1896 task.jl:969 (sys.so+0x5cd218)
#3 schedule task.jl:983 (sys.so+0x892294)
#4 macro expansion threadingconstructs.jl:522 (sys.so+0x892294)
#5 julia_start_profile_listener_60681 Base.jl:355 (sys.so+0x892294)
#6 julia___init___60641 Base.jl:392 (sys.so+0x1178dc)
#7 jfptr___init___60642 <null> (sys.so+0x118134)
#8 _jl_invoke /home/user/c/julia/src/gf.c (libjulia-internal.so.1.13+0x5e9a4)
#9 ijl_apply_generic /home/user/c/julia/src/gf.c:3892:12 (libjulia-internal.so.1.13+0x5e9a4)
JuliaLang#10 jl_apply /home/user/c/julia/src/julia.h:2343:12 (libjulia-internal.so.1.13+0xbba74)
JuliaLang#11 jl_module_run_initializer /home/user/c/julia/src/toplevel.c:68:13 (libjulia-internal.so.1.13+0xbba74)
JuliaLang#12 _finish_jl_init_ /home/user/c/julia/src/init.c:632:13 (libjulia-internal.so.1.13+0x9c0fc)
JuliaLang#13 ijl_init_ /home/user/c/julia/src/init.c:783:5 (libjulia-internal.so.1.13+0x9bcf4)
JuliaLang#14 jl_repl_entrypoint /home/user/c/julia/src/jlapi.c:1125:5 (libjulia-internal.so.1.13+0xf7ec8)
JuliaLang#15 jl_load_repl /home/user/c/julia/cli/loader_lib.c:601:12 (libjulia.so.1.13+0x11934)
JuliaLang#16 main /home/user/c/julia/cli/loader_exe.c:58:15 (julia+0x10dc20)
Previous write of size 8 at 0xffff86bec058 by thread T2:
#0 IntrusiveLinkedListSynchronized task.jl:863 (sys.so+0x78d220)
#1 macro expansion task.jl:932 (sys.so+0x78d220)
#2 macro expansion lock.jl:376 (sys.so+0x78d220)
#3 julia_workqueue_for_1933 task.jl:924 (sys.so+0x78d220)
#4 julia_wait_2048 task.jl:1204 (sys.so+0x6255ac)
#5 julia_task_done_hook_49205 task.jl:839 (sys.so+0x128fdc0)
#6 jfptr_task_done_hook_49206 <null> (sys.so+0x902218)
#7 _jl_invoke /home/user/c/julia/src/gf.c (libjulia-internal.so.1.13+0x5e9a4)
#8 ijl_apply_generic /home/user/c/julia/src/gf.c:3892:12 (libjulia-internal.so.1.13+0x5e9a4)
#9 jl_apply /home/user/c/julia/src/julia.h:2343:12 (libjulia-internal.so.1.13+0x9c79c)
JuliaLang#10 jl_finish_task /home/user/c/julia/src/task.c:345:13 (libjulia-internal.so.1.13+0x9c79c)
JuliaLang#11 jl_threadfun /home/user/c/julia/src/scheduler.c:122:5 (libjulia-internal.so.1.13+0xe7db8)
Thread T2 (tid=6824, running) created by main thread at:
#0 pthread_create <null> (julia+0x85f88)
#1 uv_thread_create_ex /workspace/srcdir/libuv/src/unix/thread.c:172 (libjulia-internal.so.1.13+0x1a8d70)
#2 _finish_jl_init_ /home/user/c/julia/src/init.c:618:5 (libjulia-internal.so.1.13+0x9c010)
#3 ijl_init_ /home/user/c/julia/src/init.c:783:5 (libjulia-internal.so.1.13+0x9bcf4)
#4 jl_repl_entrypoint /home/user/c/julia/src/jlapi.c:1125:5 (libjulia-internal.so.1.13+0xf7ec8)
#5 jl_load_repl /home/user/c/julia/cli/loader_lib.c:601:12 (libjulia.so.1.13+0x11934)
#6 main /home/user/c/julia/cli/loader_exe.c:58:15 (julia+0x10dc20)
SUMMARY: ThreadSanitizer: data race Base_compiler.jl:57 in getproperty
==================
```
adienes
pushed a commit
that referenced
this pull request
Oct 10, 2025
Use an atomic fetch and add to fix a data race in `Module()` identified by tsan: ``` ./usr/bin/julia -t4,0 --gcthreads=1 -e 'Threads.@threads for i=1:100 Module() end' ================== WARNING: ThreadSanitizer: data race (pid=5575) Write of size 4 at 0xffff9bf9bd28 by thread T9: #0 jl_new_module__ /home/user/c/julia/src/module.c:487:22 (libjulia-internal.so.1.13+0x897d4) #1 jl_new_module_ /home/user/c/julia/src/module.c:527:22 (libjulia-internal.so.1.13+0x897d4) #2 jl_f_new_module /home/user/c/julia/src/module.c:649:22 (libjulia-internal.so.1.13+0x8a968) #3 <null> <null> (0xffff76a21164) #4 <null> <null> (0xffff76a1f074) #5 <null> <null> (0xffff76a1f0c4) #6 _jl_invoke /home/user/c/julia/src/gf.c (libjulia-internal.so.1.13+0x5ea04) #7 ijl_apply_generic /home/user/c/julia/src/gf.c:3892:12 (libjulia-internal.so.1.13+0x5ea04) #8 jl_apply /home/user/c/julia/src/julia.h:2343:12 (libjulia-internal.so.1.13+0x9e4c4) #9 start_task /home/user/c/julia/src/task.c:1249:19 (libjulia-internal.so.1.13+0x9e4c4) Previous write of size 4 at 0xffff9bf9bd28 by thread T10: #0 jl_new_module__ /home/user/c/julia/src/module.c:487:22 (libjulia-internal.so.1.13+0x897d4) #1 jl_new_module_ /home/user/c/julia/src/module.c:527:22 (libjulia-internal.so.1.13+0x897d4) #2 jl_f_new_module /home/user/c/julia/src/module.c:649:22 (libjulia-internal.so.1.13+0x8a968) #3 <null> <null> (0xffff76a21164) #4 <null> <null> (0xffff76a1f074) #5 <null> <null> (0xffff76a1f0c4) #6 _jl_invoke /home/user/c/julia/src/gf.c (libjulia-internal.so.1.13+0x5ea04) #7 ijl_apply_generic /home/user/c/julia/src/gf.c:3892:12 (libjulia-internal.so.1.13+0x5ea04) #8 jl_apply /home/user/c/julia/src/julia.h:2343:12 (libjulia-internal.so.1.13+0x9e4c4) #9 start_task /home/user/c/julia/src/task.c:1249:19 (libjulia-internal.so.1.13+0x9e4c4) Location is global 'jl_new_module__.mcounter' of size 4 at 0xffff9bf9bd28 (libjulia-internal.so.1.13+0x3dbd28) ``` (cherry picked from commit 9039555)
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