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data-race/rare crash with with IO #751

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avsm opened this issue Aug 27, 2024 · 3 comments
Open

data-race/rare crash with with IO #751

avsm opened this issue Aug 27, 2024 · 3 comments

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@avsm
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avsm commented Aug 27, 2024

Still trying to track down exactly what is causing this, but it triggers now with a small testcase in 5.2.0 and 5.3.0+trunk on x86_64 with the following program:

let () =
  Eio_main.run @@ fun env ->
  Eio.Switch.run @@ fun sw ->
  let pool = Eio.Executor_pool.create
      ~sw (Eio.Stdenv.domain_mgr env)
      ~domain_count:(Domain.recommended_domain_count () - 1)
  in
  let cwd = Eio.Stdenv.cwd env in
  let temp_files = List.init 1000 (fun _ ->
    let f = Filename.temp_file ~temp_dir:"." "stresstest" "" in
    let p = Eio.Path.(cwd / (Filename.basename f)) in
    Eio.Path.with_open_out ~create:`Never p (fun f ->
      let _ = Eio.File.pwrite_all f ~file_offset:(Optint.Int63.of_int 2000) [Cstruct.create 4096] in
      ()
    );
    p
  ) in
  let process m () =
    for _ = 0 to 1000 do
      let _ = String.make 10000 'a' in
      ignore(Eio.Path.load m)
    done
  in
  Eio.Fiber.List.iter ~max_fibers:100 (fun msg ->
    Eio.Executor_pool.submit_exn pool ~weight:0.5 (process msg)
  ) temp_files;
  List.iter Eio.Path.unlink temp_files

built with:

(executable
 (public_name test)
 (name test)
 (flags (:standard -g -runtime-variant d))
 (libraries eio_main))

It triggers the following data race reliably on Linux:

==================
WARNING: ThreadSanitizer: data race (pid=912737)
  Write of size 8 at 0x7f8561e08d08 by thread T16 (mutexes: write M0):
    #0 camlEio__core__Switch.dec_fibers_1051 lib_eio/core/switch.ml:71 (test.exe+0x1978e0) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #1 camlStdlib__Fun.finally_no_exn_330 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:30 (test.exe+0x247652) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #2 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:35 (test.exe+0x2475ae) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #3 caml_runstack <null> (test.exe+0x2f2d91) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #4 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #5 camlEio_posix__Sched.run_1355 lib_eio_posix/sched.ml:381 (test.exe+0x119644) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #6 camlEio_posix__Sched.with_sched_1218 lib_eio_posix/sched.ml:258 (test.exe+0x118959) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #7 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #8 camlStdlib__Domain.body_741 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/domain.ml:266 (test.exe+0x2258ef) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #9 caml_start_program <null> (test.exe+0x2f25b3) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #10 caml_callback_exn runtime/callback.c:205 (test.exe+0x2a1973) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #11 caml_callback_res runtime/callback.c:320 (test.exe+0x2a29b4) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #12 domain_thread_func runtime/domain.c:1245 (test.exe+0x2a79a5) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)

  Previous atomic read of size 8 at 0x7f8561e08d08 by thread T40587 (mutexes: write M1, write M2):
    #0 mark_stack_push_block runtime/major_gc.c:871 (test.exe+0x2c815b) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #1 caml_darken runtime/major_gc.c:1208 (test.exe+0x2ca02e) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #2 caml_darken runtime/major_gc.c:1186 (test.exe+0x2ca02e)
    #3 scan_stack_frames runtime/fiber.c:280 (test.exe+0x2b1756) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #4 caml_scan_stack runtime/fiber.c:301 (test.exe+0x2b1756)
    #5 caml_darken_cont runtime/major_gc.c:1177 (test.exe+0x2c9d9f) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #6 do_some_marking runtime/major_gc.c:1009 (test.exe+0x2cafa7) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #7 mark runtime/major_gc.c:1124 (test.exe+0x2cb199) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #8 major_collection_slice runtime/major_gc.c:1704 (test.exe+0x2cbcb7) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #9 caml_major_collection_slice runtime/major_gc.c:1884 (test.exe+0x2ccec4) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #10 caml_poll_gc_work runtime/domain.c:1874 (test.exe+0x2a8990) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #11 stw_handler runtime/domain.c:1502 (test.exe+0x2a8d81) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #12 handle_incoming runtime/domain.c:351 (test.exe+0x2a8d81)
    #13 caml_handle_incoming_interrupts runtime/domain.c:364 (test.exe+0x2a9648) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #14 caml_try_run_on_all_domains_with_spin_work runtime/domain.c:1606 (test.exe+0x2a9648)
    #15 caml_try_run_on_all_domains runtime/domain.c:1717 (test.exe+0x2a97f3) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #16 major_collection_slice runtime/major_gc.c:1866 (test.exe+0x2cc892) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #17 caml_major_collection_slice runtime/major_gc.c:1884 (test.exe+0x2ccec4) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #18 caml_poll_gc_work runtime/domain.c:1874 (test.exe+0x2a8990) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #19 caml_handle_gc_interrupt runtime/domain.c:1901 (test.exe+0x2aa01f) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #20 caml_do_pending_actions_res runtime/signals.c:338 (test.exe+0x2e5410) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #21 caml_alloc_small_dispatch runtime/minor_gc.c:896 (test.exe+0x2da4b4) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #22 caml_garbage_collection runtime/signals_nat.c:86 (test.exe+0x2f7140) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #23 caml_call_gc <null> (test.exe+0x2f219f) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #24 camlLwt_dllist.add_r_311 src/lwt_dllist.ml:69 (test.exe+0x1c84c4) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #25 camlEio__core__Switch.on_release_full_1241 lib_eio/core/switch.ml:184 (test.exe+0x198c58) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #26 camlEio_unix__Fd.of_unix_650 lib_eio/core/switch.ml:199 (test.exe+0x14c731) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #27 camlEio_posix__Low_level.with_state_1607 lib_eio_posix/low_level.ml:284 (test.exe+0x11d49d) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #28 camlEio_unix__Thread_pool.fun_749 lib_eio/unix/thread_pool.ml:71 (test.exe+0x14a677) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #29 camlThread.fun_769 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/otherlibs/systhreads/thread.ml:48 (test.exe+0x153700) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #30 caml_start_program <null> (test.exe+0x2f25b3) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #31 caml_callback_exn runtime/callback.c:205 (test.exe+0x2a1973) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #32 caml_thread_start /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/otherlibs/systhreads/st_stubs.c:648 (test.exe+0x280703) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)

  Mutex M0 (0x72b4000008e0) created at:
    #0 pthread_mutex_init ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:1315 (libtsan.so.2+0x58bfd) (BuildId: 64c1e8de04b11a7d960abd7e45f94f3b277b7779)
    #1 caml_plat_mutex_init runtime/platform.c:59 (test.exe+0x2dc362) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #2 caml_init_domains runtime/domain.c:974 (test.exe+0x2a7634) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #3 caml_init_gc runtime/gc_ctrl.c:348 (test.exe+0x2b6ab5) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #4 caml_startup_common runtime/startup_nat.c:106 (test.exe+0x2f1b37) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #5 caml_startup_common runtime/startup_nat.c:86 (test.exe+0x2f1b37)
    #6 caml_startup_exn runtime/startup_nat.c:134 (test.exe+0x2f1d3b) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #7 caml_startup runtime/startup_nat.c:139 (test.exe+0x2f1d3b)
    #8 caml_main runtime/startup_nat.c:146 (test.exe+0x2f1d3b)
    #9 main runtime/main.c:37 (test.exe+0x111239) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)

  Mutex M1 (0x72b400000d00) created at:
    #0 pthread_mutex_init ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:1315 (libtsan.so.2+0x58bfd) (BuildId: 64c1e8de04b11a7d960abd7e45f94f3b277b7779)
    #1 caml_plat_mutex_init runtime/platform.c:59 (test.exe+0x2dc362) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #2 caml_init_domains runtime/domain.c:974 (test.exe+0x2a7634) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #3 caml_init_gc runtime/gc_ctrl.c:348 (test.exe+0x2b6ab5) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #4 caml_startup_common runtime/startup_nat.c:106 (test.exe+0x2f1b37) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #5 caml_startup_common runtime/startup_nat.c:86 (test.exe+0x2f1b37)
    #6 caml_startup_exn runtime/startup_nat.c:134 (test.exe+0x2f1d3b) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #7 caml_startup runtime/startup_nat.c:139 (test.exe+0x2f1d3b)
    #8 caml_main runtime/startup_nat.c:146 (test.exe+0x2f1d3b)
    #9 main runtime/main.c:37 (test.exe+0x111239) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)

  Mutex M2 (0x720c00039030) created at:
    #0 pthread_mutex_init ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:1315 (libtsan.so.2+0x58bfd) (BuildId: 64c1e8de04b11a7d960abd7e45f94f3b277b7779)
    #1 sync_mutex_create runtime/sync_posix.h:44 (test.exe+0x2e84aa) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #2 caml_ml_mutex_new runtime/sync.c:77 (test.exe+0x2e84aa)
    #3 caml_c_call <null> (test.exe+0x2f2439) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #4 camlEio__core__Switch.create_1177 lib_eio/core/switch.ml:127 (test.exe+0x198298) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #5 camlEio__core__Switch.fun_1376 lib_eio/core/switch.ml:152 (test.exe+0x19858b) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #6 camlEio__core__Cancel.with_cc_1067 lib_eio/core/cancel.ml:118 (test.exe+0x194b3b) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #7 camlDune__exe__Test.process_822 bin/test.ml:21 (test.exe+0x115090) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #8 camlEio__Executor_pool.fun_814 lib_eio/executor_pool.ml:31 (test.exe+0x189be6) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #9 camlEio__core__Fiber.fun_1441 lib_eio/core/fiber.ml:21 (test.exe+0x19f2e6) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #10 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #11 caml_runstack <null> (test.exe+0x2f2d91) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #12 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #13 camlEio_posix__Sched.run_1355 lib_eio_posix/sched.ml:381 (test.exe+0x119644) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #14 camlEio_posix__Sched.with_sched_1218 lib_eio_posix/sched.ml:258 (test.exe+0x118959) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #15 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #16 camlStdlib__Domain.body_741 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/domain.ml:266 (test.exe+0x2258ef) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #17 caml_start_program <null> (test.exe+0x2f25b3) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #18 caml_callback_exn runtime/callback.c:205 (test.exe+0x2a1973) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #19 caml_callback_res runtime/callback.c:320 (test.exe+0x2a29b4) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #20 domain_thread_func runtime/domain.c:1245 (test.exe+0x2a79a5) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)

  Thread T16 (tid=912754, running) created by main thread at:
    #0 pthread_create ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:1022 (libtsan.so.2+0x5a267) (BuildId: 64c1e8de04b11a7d960abd7e45f94f3b277b7779)
    #1 caml_domain_spawn runtime/domain.c:1294 (test.exe+0x2a9cbe) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #2 caml_c_call <null> (test.exe+0x2f2439) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #3 camlStdlib__Domain.spawn_736 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/domain.ml:284 (test.exe+0x225806) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #4 camlEio_posix__Domain_mgr.fun_1449 lib_eio_posix/domain_mgr.ml:117 (test.exe+0x128f6e) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #5 camlEio_posix__Sched.fun_1761 lib_eio_posix/sched.ml:355 (test.exe+0x119f4c) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #6 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #7 camlEio_posix__Sched.run_1355 lib_eio_posix/sched.ml:381 (test.exe+0x119644) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #8 camlEio_posix__Sched.with_sched_1218 lib_eio_posix/sched.ml:258 (test.exe+0x118959) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #9 camlDune__exe__Test.entry bin/test.ml:2 (test.exe+0x115211) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #10 caml_program <null> (test.exe+0x111e6e) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #11 caml_start_program <null> (test.exe+0x2f25b3) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #12 caml_startup_common runtime/startup_nat.c:127 (test.exe+0x2f1c58) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #13 caml_startup_common runtime/startup_nat.c:86 (test.exe+0x2f1c58)
    #14 caml_startup_exn runtime/startup_nat.c:134 (test.exe+0x2f1d3b) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #15 caml_startup runtime/startup_nat.c:139 (test.exe+0x2f1d3b)
    #16 caml_main runtime/startup_nat.c:146 (test.exe+0x2f1d3b)
    #17 main runtime/main.c:37 (test.exe+0x111239) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)

  Thread T40587 (tid=953475, finished) created by thread T24 at:
    #0 pthread_create ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:1022 (libtsan.so.2+0x5a267) (BuildId: 64c1e8de04b11a7d960abd7e45f94f3b277b7779)
    #1 st_thread_create /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/otherlibs/systhreads/st_pthreads.h:50 (test.exe+0x280885) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #2 caml_thread_new /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/otherlibs/systhreads/st_stubs.c:707 (test.exe+0x280885)
    #3 caml_c_call <null> (test.exe+0x2f2439) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #4 camlThread.create_288 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/otherlibs/systhreads/thread.ml:45 (test.exe+0x153679) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #5 camlEio_unix__Thread_pool.make_thread_481 lib_eio/unix/thread_pool.ml:64 (test.exe+0x14a542) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #6 camlEio_unix__Thread_pool.submit_579 lib_eio/unix/thread_pool.ml:119 (test.exe+0x14ac39) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #7 camlEio_posix__Sched.fun_1791 lib_eio_posix/sched.ml:372 (test.exe+0x11a217) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #8 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #9 camlEio_posix__Sched.run_1355 lib_eio_posix/sched.ml:381 (test.exe+0x119644) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #10 camlEio_posix__Sched.with_sched_1218 lib_eio_posix/sched.ml:258 (test.exe+0x118959) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #11 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #12 camlStdlib__Domain.body_741 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/domain.ml:266 (test.exe+0x2258ef) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #13 caml_start_program <null> (test.exe+0x2f25b3) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #14 caml_callback_exn runtime/callback.c:205 (test.exe+0x2a1973) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #15 caml_callback_res runtime/callback.c:320 (test.exe+0x2a29b4) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)
    #16 domain_thread_func runtime/domain.c:1245 (test.exe+0x2a79a5) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)

SUMMARY: ThreadSanitizer: data race lib_eio/core/switch.ml:71 in camlEio__core__Switch.dec_fibers_1051
==================
==================                                                                                                                                                                                                                
WARNING: ThreadSanitizer: data race (pid=912737)                                                                                                                                                                                  
  Atomic read of size 8 at 0x7f8560b79f48 by thread T12 (mutexes: write M0):                                                                                                                                                      
    #0 mark_stack_push_block runtime/major_gc.c:871 (test.exe+0x2c815b) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                       
    #1 caml_darken runtime/major_gc.c:1208 (test.exe+0x2ca02e) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                
    #2 caml_darken runtime/major_gc.c:1186 (test.exe+0x2ca02e)                                                                                                                                                                    
    #3 scan_stack_frames runtime/fiber.c:280 (test.exe+0x2b1756) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                              
    #4 caml_scan_stack runtime/fiber.c:301 (test.exe+0x2b1756)                                                                                                                                                                    
    #5 caml_darken_cont runtime/major_gc.c:1177 (test.exe+0x2c9d9f) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                           
    #6 do_some_marking runtime/major_gc.c:1009 (test.exe+0x2cafa7) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                            
    #7 mark runtime/major_gc.c:1124 (test.exe+0x2cb199) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                       
    #8 major_collection_slice runtime/major_gc.c:1704 (test.exe+0x2cbcb7) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                     
    #9 caml_major_collection_slice runtime/major_gc.c:1884 (test.exe+0x2ccec4) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                
    #10 caml_poll_gc_work runtime/domain.c:1874 (test.exe+0x2a8990) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                           
    #11 caml_handle_gc_interrupt runtime/domain.c:1901 (test.exe+0x2aa01f) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                    
    #12 caml_check_urgent_gc runtime/minor_gc.c:950 (test.exe+0x2da709) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                       
    #13 caml_alloc_string runtime/alloc.c:186 (test.exe+0x295bf4) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                             
    #14 caml_create_bytes runtime/str.c:78 (test.exe+0x2e729b) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                
    #15 caml_c_call <null> (test.exe+0x2f2439) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                                
    #16 camlCstruct.copy_to_string_1171 lib/cstruct.ml:207 (test.exe+0x1cd138) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                
    #17 camlEio__Path.fun_2315 lib_eio/path.ml:143 (test.exe+0x17ffba) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                        
    #18 camlEio__core__Switch.run_internal_1180 lib_eio/core/switch.ml:133 (test.exe+0x198393) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                
    #19 camlEio__core__Cancel.with_cc_1067 lib_eio/core/cancel.ml:118 (test.exe+0x194b3b) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                     
    #20 camlDune__exe__Test.process_822 bin/test.ml:21 (test.exe+0x115090) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                    
    #21 camlEio__Executor_pool.fun_814 lib_eio/executor_pool.ml:31 (test.exe+0x189be6) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                        
    #22 camlEio__core__Fiber.fun_1441 lib_eio/core/fiber.ml:21 (test.exe+0x19f2e6) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                            
    #23 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                            
    #24 caml_runstack <null> (test.exe+0x2f2d91) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                              
    #25 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                            
    #26 camlEio_posix__Sched.run_1355 lib_eio_posix/sched.ml:381 (test.exe+0x119644) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                          
    #27 camlEio_posix__Sched.with_sched_1218 lib_eio_posix/sched.ml:258 (test.exe+0x118959) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                   
    #28 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                            
    #29 camlStdlib__Domain.body_741 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/domain.ml:266 (test.exe+0x2258ef) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                        
    #30 caml_start_program <null> (test.exe+0x2f25b3) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                         
    #31 caml_callback_exn runtime/callback.c:205 (test.exe+0x2a1973) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                          
    #32 caml_callback_res runtime/callback.c:320 (test.exe+0x2a29b4) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                          
    #33 domain_thread_func runtime/domain.c:1245 (test.exe+0x2a79a5) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                          
                                                                                                                                                                                                                                  
  Previous write of size 8 at 0x7f8560b79f48 by thread T28 (mutexes: write M1):                                                                                                                                                   
    #0 camlEio__core__Switch.dec_fibers_1051 lib_eio/core/switch.ml:71 (test.exe+0x1978e0) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                    
    #1 camlStdlib__Fun.finally_no_exn_330 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:30 (test.exe+0x247652) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                      
    #2 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:35 (test.exe+0x2475ae) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                             
    #3 caml_runstack <null> (test.exe+0x2f2d91) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                               
    #4 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                             
    #5 camlEio_posix__Sched.run_1355 lib_eio_posix/sched.ml:381 (test.exe+0x119644) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                           
    #6 camlEio_posix__Sched.with_sched_1218 lib_eio_posix/sched.ml:258 (test.exe+0x118959) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                    
    #7 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                             
    #8 camlStdlib__Domain.body_741 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/domain.ml:266 (test.exe+0x2258ef) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                         
    #9 caml_start_program <null> (test.exe+0x2f25b3) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                          
    #10 caml_callback_exn runtime/callback.c:205 (test.exe+0x2a1973) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                          
    #11 caml_callback_res runtime/callback.c:320 (test.exe+0x2a29b4) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                          
    #12 domain_thread_func runtime/domain.c:1245 (test.exe+0x2a79a5) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                          

  Mutex M0 (0x72b4000006d0) created at:                                                                          
    #0 pthread_mutex_init ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:1315 (libtsan.so.2+0x58bfd) (BuildId: 64c1e8de04b11a7d960abd7e45f94f3b277b7779)                                                           
    #1 caml_plat_mutex_init runtime/platform.c:59 (test.exe+0x2dc362) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                         
    #2 caml_init_domains runtime/domain.c:974 (test.exe+0x2a7634) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                             
    #3 caml_init_gc runtime/gc_ctrl.c:348 (test.exe+0x2b6ab5) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                 
    #4 caml_startup_common runtime/startup_nat.c:106 (test.exe+0x2f1b37) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                      
    #5 caml_startup_common runtime/startup_nat.c:86 (test.exe+0x2f1b37)                                          
    #6 caml_startup_exn runtime/startup_nat.c:134 (test.exe+0x2f1d3b) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                         
    #7 caml_startup runtime/startup_nat.c:139 (test.exe+0x2f1d3b)                                                
    #8 caml_main runtime/startup_nat.c:146 (test.exe+0x2f1d3b)                                                   
    #9 main runtime/main.c:37 (test.exe+0x111239) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                             

  Mutex M1 (0x72b400000f10) created at:                                                                          
    #0 pthread_mutex_init ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:1315 (libtsan.so.2+0x58bfd) (BuildId: 64c1e8de04b11a7d960abd7e45f94f3b277b7779)                                                           
    #1 caml_plat_mutex_init runtime/platform.c:59 (test.exe+0x2dc362) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                         
    #2 caml_init_domains runtime/domain.c:974 (test.exe+0x2a7634) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                             
    #3 caml_init_gc runtime/gc_ctrl.c:348 (test.exe+0x2b6ab5) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                 
    #4 caml_startup_common runtime/startup_nat.c:106 (test.exe+0x2f1b37) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                      
    #5 caml_startup_common runtime/startup_nat.c:86 (test.exe+0x2f1b37)                                          
    #6 caml_startup_exn runtime/startup_nat.c:134 (test.exe+0x2f1d3b) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                         
    #7 caml_startup runtime/startup_nat.c:139 (test.exe+0x2f1d3b)                                                
    #8 caml_main runtime/startup_nat.c:146 (test.exe+0x2f1d3b)                                                   
    #9 main runtime/main.c:37 (test.exe+0x111239) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                             

  Thread T12 (tid=912750, running) created by main thread at:                                                    
    #0 pthread_create ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:1022 (libtsan.so.2+0x5a267) (BuildId: 64c1e8de04b11a7d960abd7e45f94f3b277b7779)                                                               
    #1 caml_domain_spawn runtime/domain.c:1294 (test.exe+0x2a9cbe) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                            
    #2 caml_c_call <null> (test.exe+0x2f2439) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                                 
    #3 camlStdlib__Domain.spawn_736 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/domain.ml:284 (test.exe+0x225806) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                        
    #4 camlEio_posix__Domain_mgr.fun_1449 lib_eio_posix/domain_mgr.ml:117 (test.exe+0x128f6e) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                 
    #5 camlEio_posix__Sched.fun_1761 lib_eio_posix/sched.ml:355 (test.exe+0x119f4c) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                           
    #6 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                             
    #7 camlEio_posix__Sched.run_1355 lib_eio_posix/sched.ml:381 (test.exe+0x119644) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                           
    #8 camlEio_posix__Sched.with_sched_1218 lib_eio_posix/sched.ml:258 (test.exe+0x118959) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                    
    #9 camlDune__exe__Test.entry bin/test.ml:2 (test.exe+0x115211) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                            
    #10 caml_program <null> (test.exe+0x111e6e) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                               
    #11 caml_start_program <null> (test.exe+0x2f25b3) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                         
    #12 caml_startup_common runtime/startup_nat.c:127 (test.exe+0x2f1c58) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                     
    #13 caml_startup_common runtime/startup_nat.c:86 (test.exe+0x2f1c58)                                         
    #14 caml_startup_exn runtime/startup_nat.c:134 (test.exe+0x2f1d3b) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                        
    #15 caml_startup runtime/startup_nat.c:139 (test.exe+0x2f1d3b)                                               
    #16 caml_main runtime/startup_nat.c:146 (test.exe+0x2f1d3b)                                                  
    #17 main runtime/main.c:37 (test.exe+0x111239) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                            

  Thread T28 (tid=912766, running) created by main thread at:                                                    
    #0 pthread_create ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:1022 (libtsan.so.2+0x5a267) (BuildId: 64c1e8de04b11a7d960abd7e45f94f3b277b7779)                                                               
    #1 caml_domain_spawn runtime/domain.c:1294 (test.exe+0x2a9cbe) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                            
    #2 caml_c_call <null> (test.exe+0x2f2439) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                                 
    #3 camlStdlib__Domain.spawn_736 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/domain.ml:284 (test.exe+0x225806) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                        
    #4 camlEio_posix__Domain_mgr.fun_1449 lib_eio_posix/domain_mgr.ml:117 (test.exe+0x128f6e) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                 
    #5 camlEio_posix__Sched.fun_1761 lib_eio_posix/sched.ml:355 (test.exe+0x119f4c) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                           
    #6 camlStdlib__Fun.protect_326 /home/avsm/.opam/5.3.0+tsan/.opam-switch/build/ocaml-variants.5.3.0+trunk/stdlib/fun.ml:34 (test.exe+0x24753a) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                             
    #7 camlEio_posix__Sched.run_1355 lib_eio_posix/sched.ml:381 (test.exe+0x119644) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                           
    #8 camlEio_posix__Sched.with_sched_1218 lib_eio_posix/sched.ml:258 (test.exe+0x118959) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                    
    #9 camlDune__exe__Test.entry bin/test.ml:2 (test.exe+0x115211) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                            
    #10 caml_program <null> (test.exe+0x111e6e) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                               
    #11 caml_start_program <null> (test.exe+0x2f25b3) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                         
    #12 caml_startup_common runtime/startup_nat.c:127 (test.exe+0x2f1c58) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                     
    #13 caml_startup_common runtime/startup_nat.c:86 (test.exe+0x2f1c58)                                         
    #14 caml_startup_exn runtime/startup_nat.c:134 (test.exe+0x2f1d3b) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                        
    #15 caml_startup runtime/startup_nat.c:139 (test.exe+0x2f1d3b)                                               
    #16 caml_main runtime/startup_nat.c:146 (test.exe+0x2f1d3b)                                                  
    #17 main runtime/main.c:37 (test.exe+0x111239) (BuildId: 228a6c9ad794879ebbb16feade2d642f12a5cf5c)                                                                                                                            

SUMMARY: ThreadSanitizer: data race runtime/major_gc.c:871 in mark_stack_push_block                                                                                                                                               
==================

It happens with both the uring and posix backend
@talex5
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talex5 commented Aug 27, 2024

The fact that it's racing with a read by the GC suggests these tsan reports are both false positives. I would expect it's perfectly reasonable for one domain to be examining the block's fields during marking in a major slice while another one is updating the count.

@OlivierNicole might know for sure.

Does it actually crash, or just give warnings from tsan? (on my machine, I only see the warnings)

@avsm
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avsm commented Aug 27, 2024

I'm trying to reproduce the crash but have only gotten it once on the bigger program from which I extracted this testcase

ThreadSanitizer:DEADLYSIGNAL                                                                                                                                 
==800191==ERROR: ThreadSanitizer: SEGV on unknown address 0x557e838d93a4 (pc 0x557e83a6f782 bp 0x722c0001ff80 sp 0x7f5624dff160 T800204)
==800191==The signal is caused by a WRITE memory access.                                                                                                     
    #0 oldify_one runtime/minor_gc.c:252 (main.exe+0x413782) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d)         
    #1 caml_empty_minor_heap_promote runtime/minor_gc.c:561 (main.exe+0x41495a) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d)
    #2 caml_stw_empty_minor_heap_no_major_slice runtime/minor_gc.c:792 (main.exe+0x414fc0) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d)
    #3 caml_stw_empty_minor_heap runtime/minor_gc.c:823 (main.exe+0x4152b6) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d)
    #4 stw_handler runtime/domain.c:1486 (main.exe+0x3eb508) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d)         
    #5 handle_incoming runtime/domain.c:351 (main.exe+0x3eb508)                                                                                              
    #6 caml_handle_incoming_interrupts runtime/domain.c:364 (main.exe+0x3ec18b) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d)
    #7 caml_handle_gc_interrupt runtime/domain.c:1897 (main.exe+0x3ec18b)                                                                                    
    #8 caml_do_pending_actions_res runtime/signals.c:338 (main.exe+0x41e06c) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d)
    #9 caml_alloc_small_dispatch runtime/minor_gc.c:896 (main.exe+0x415514) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d)
    #10 caml_garbage_collection runtime/signals_nat.c:86 (main.exe+0x42dd78) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d)
    #11 caml_call_gc <null> (main.exe+0x42a165) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d)                      
    #12 camlBase64_rfc2045.pp_base64_761 src/base64_rfc2045.ml:252 (main.exe+0x2ba8a6) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d)
    #13 camlMrmime__B64.parser_898 src/base64_rfc2045.ml:278 (main.exe+0x27d255) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d)
    #14 camlMrmime__B64.parser_898 lib/b64.ml:98 (main.exe+0x27d3a3) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d) 
    #15 camlMrmime__B64.parser_898 lib/b64.ml:98 (main.exe+0x27d3a3) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d) 
    #16 camlMrmime__B64.parser_898 lib/b64.ml:98 (main.exe+0x27d3a3) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d) 
    #17 camlMrmime__B64.parser_898 lib/b64.ml:98 (main.exe+0x27d3a3) (BuildId: 15be3c35d13b78db78a598b67ef2ce684d8ad79d)

@talex5
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talex5 commented Aug 27, 2024

Here's a simpler way to trigger the tsan error (no IO, works on Linux and Posix backends):

open Eio.Std

let run_worker () =
  Switch.run ~name:"run_worker" @@ fun sw ->
  while true do
    Fiber.fork ~sw (fun () ->
        for _ = 0 to 1000 do
          ignore (String.make 10000 'a')
        done
      );
  done

let () =
  Eio_main.run @@ fun env ->
  Eio.Switch.run @@ fun sw ->
  let domain_mgr = Eio.Stdenv.domain_mgr env in
  for _ = 1 to 7 do
    Fiber.fork_daemon ~sw (fun () -> Eio.Domain_manager.run domain_mgr run_worker)
  done;
  for _ = 1 to 10000 do
    Fiber.fork ~sw (fun () ->
        for _ = 1 to 1000 do
          ignore (Sys.opaque_identity ())
        done
      )
  done

talex5 added a commit to talex5/eio that referenced this issue Sep 6, 2024
@talex5
eio_linux: avoid triggering a TSan warning
7c5da37 
TSan warns that setting `statx_works` races with users of it. This isn't
really a problem, because we always set it to the same value, but it's
distracting when looking for other bugs.

Reported by Anil Madhavapeddy in ocaml-multicore#751.
@talex5 talex5 mentioned this issue Sep 6, 2024
Merged
talex5 added a commit to talex5/eio that referenced this issue Sep 6, 2024
@talex5
eio_linux: avoid triggering a TSan warning
9ca440a 
TSan warns that setting `statx_works` races with users of it. This isn't
really a problem, because we always set it to the same value, but it's
distracting when looking for other bugs.

Reported by Anil Madhavapeddy in ocaml-multicore#751.
@talex5 talex5 mentioned this issue Sep 9, 2024
Open
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@avsm @talex5