window.gc(): DomRefCell<T> already borrowed: BorrowError

[mateon1]

Found by accident while using domato.

This is a relatively recent breakage, window.gc() used to work just fine a few months ago.

<script>window.gc()</script>

VMware, Inc.
softpipe
3.3 (Core Profile) Mesa 17.3.0-devel
DomRefCell<T> already mutably borrowed: BorrowError (thread ScriptThread PipelineId { namespace_id: PipelineNamespaceId(0), index: PipelineIndex(NonZero(NonZero(1))) }, at libcore/result.rs:916)
stack backtrace:
   0:     0x55555bd1cce4 - backtrace::backtrace::libunwind::trace::h79984cabe80721dc
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.2/src/backtrace/libunwind.rs:53
                         - backtrace::backtrace::trace::h10c59b076f73358b
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.2/src/backtrace/mod.rs:42
   1:     0x55555bd1446c - backtrace::capture::Backtrace::new::haef9cefb7535bc7c
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.2/src/capture.rs:64
   2:     0x55555597b316 - servo::main::{{closure}}::h3cd5e9106607e7fe
                        at ports/servo/main.rs:146
   3:     0x55555bd30125 - std::panicking::rust_panic_with_hook::haa00f5a9417cd684
                        at libstd/panicking.rs:577
   4:     0x55555bd2ffae - std::panicking::begin_panic::ha956683198499384
                        at libstd/panicking.rs:537
   5:     0x55555bd2feaa - std::panicking::begin_panic_fmt::h587e116719f14631
                        at libstd/panicking.rs:521
   6:     0x55555bd2fe42 - rust_begin_unwind
                        at libstd/panicking.rs:497
   7:     0x55555bd64630 - core::panicking::panic_fmt::h1d64949939b0af2f
                        at libcore/panicking.rs:71
   8:     0x555557e1bdab - core::result::unwrap_failed::h06dbaa81bf987af3
                        at /checkout/src/libcore/macros.rs:23
   9:     0x555557db92e4 - <core::result::Result<T, E>>::expect::h5589b06e1acd171f
                        at /checkout/src/libcore/result.rs:809
  10:     0x555557ac5375 - <script::dom::bindings::cell::DomRefCell<T>>::borrow::h10758e3ad589befe
                        at components/script/dom/bindings/cell.rs:70
  11:     0x555557ad61e8 - <script::dom::bindings::cell::DomRefCell<T> as script::dom::bindings::trace::JSTraceable>::trace::hd4724263efc5033f
                        at components/script/dom/bindings/trace.rs:209
  12:     0x55555716d458 - <script::script_thread::ScriptThread as script::dom::bindings::trace::JSTraceable>::trace::hb65cd1155a4a9d14
                        at components/script/script_thread.rs:389
  13:     0x55555732f2d5 - script::script_thread::trace_thread::{{closure}}::hc51be3a93dc8d01c
                        at components/script/script_thread.rs:138
  14:     0x55555815ddd2 - <std::thread::local::LocalKey<T>>::try_with::hca19a1a28d15340e
                        at /checkout/src/libstd/thread/local.rs:377
  15:     0x555557f313dc - <std::thread::local::LocalKey<T>>::with::h86c4b7d085571e1f
                        at /checkout/src/libstd/thread/local.rs:288
  16:     0x55555714d423 - script::script_thread::trace_thread::h3d1efaa40566f34d
                        at components/script/script_thread.rs:135
  17:     0x55555773dcf5 - script::script_runtime::trace_rust_roots::hd1689110d0e1089e
                        at components/script/script_runtime.rs:428
  18:     0x55555b8f4ba4 - _ZN2js2gc9GCRuntime11markRuntimeEP8JSTracerNS1_18TraceOrMarkRuntimeERNS_26AutoLockForExclusiveAccessE
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/gc/RootMarking.cpp:343
  19:     0x55555b45764d - _ZN2js2gc9GCRuntime14beginMarkPhaseEN2JS8gcreason6ReasonERNS_26AutoLockForExclusiveAccessE
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/jsgc.cpp:3907
  20:     0x55555b45e577 - _ZN2js2gc9GCRuntime23incrementalCollectSliceERNS_11SliceBudgetEN2JS8gcreason6ReasonERNS_26AutoLockForExclusiveAccessE
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/jsgc.cpp:5889
  21:     0x55555b45f2de - _ZN2js2gc9GCRuntime7gcCycleEbRNS_11SliceBudgetEN2JS8gcreason6ReasonE
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/jsgc.cpp:6174
  22:     0x55555b45f81f - _ZN2js2gc9GCRuntime7collectEbNS_11SliceBudgetEN2JS8gcreason6ReasonE
  24:     0x55555b39996f - _Z5JS_GCP9JSRuntime
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/jsapi.cpp:1340
  25:     0x55555693d42e - <script::dom::window::Window as script::dom::bindings::codegen::Bindings::WindowBinding::WindowBinding::WindowMethods>::Gc::h52eeff85a6a6c2de
                        at components/script/dom/window.rs:806
  26:     0x555556f9a2cb - script::dom::bindings::codegen::Bindings::WindowBinding::WindowBinding::gc::{{closure}}::hea78f2b66cba4081
                        at /shared/dev/rust/servo/target/debug/build/script-c42abaa61a41d086/out/Bindings/WindowBinding.rs:2605
  27:     0x55555645f61c - core::ops::function::FnOnce::call_once::ha665ccf27c6bf004
                        at /checkout/src/libcore/ops/function.rs:223
  28:     0x5555571ac64a - <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::hd50d3d0dc3bfc1a1
                        at /checkout/src/libstd/panic.rs:293
  29:     0x555556cc3054 - std::panicking::try::do_call::h44c3f521c6aa394e
                        at /checkout/src/libstd/panicking.rs:479
  30:     0x55555bd58e7e - __rust_maybe_catch_panic
                        at libpanic_unwind/lib.rs:102
  31:     0x555556c27d05 - std::panicking::try::h970c3cbe8baeb4fb
                        at /checkout/src/libstd/panicking.rs:458
  32:     0x5555571f9fc1 - std::panic::catch_unwind::hf3caccc86adf43e2
                        at /checkout/src/libstd/panic.rs:358
  33:     0x555556626e6e - mozjs::panic::wrap_panic::h921f34c3f403c5d5
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs-0.1.11/src/panic.rs:22
  34:     0x5555579d1d32 - script::dom::bindings::codegen::Bindings::WindowBinding::WindowBinding::gc::hfac9a7e0624a378d
                        at /shared/dev/rust/servo/target/debug/build/script-c42abaa61a41d086/out/Bindings/WindowBinding.rs:2601
  35:     0x55555afead28 - CallJitMethodOp
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs-0.1.11/src/jsglue.cpp:516
  36:     0x555556d958a2 - script::dom::bindings::utils::generic_call::hdd35dc4634869672
                        at components/script/dom/bindings/utils.rs:450
  37:     0x555556d9590b - script::dom::bindings::utils::generic_method::hb42754104043a424
                        at components/script/dom/bindings/utils.rs:458
  38:     0x55555b666ceb - _ZN2js12CallJSNativeEP9JSContextPFbS1_jPN2JS5ValueEERKNS2_8CallArgsE
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/jscntxtinlines.h:232
  39:     0x55555b635143 - _ZN2js23InternalCallOrConstructEP9JSContextRKN2JS8CallArgsENS_14MaybeConstructE
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/vm/Interpreter.cpp:453
  40:     0x55555b63546a - InternalCall
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/vm/Interpreter.cpp:498
  41:     0x55555b635494 - _ZN2js13CallFromStackEP9JSContextRKN2JS8CallArgsE
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/vm/Interpreter.cpp:504
  42:     0x55555b6424c0 - Interpret
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/vm/Interpreter.cpp:2873
  43:     0x55555b634dc5 - _ZN2js9RunScriptEP9JSContextRNS_8RunStateE
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/vm/Interpreter.cpp:399
  44:     0x55555b636188 - _ZN2js13ExecuteKernelEP9JSContextN2JS6HandleIP8JSScriptEER8JSObjectRKNS2_5ValueENS_16AbstractFramePtrEPS9_
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/vm/Interpreter.cpp:679
  45:     0x55555b636448 - _ZN2js7ExecuteEP9JSContextN2JS6HandleIP8JSScriptEER8JSObjectPNS2_5ValueE
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/vm/Interpreter.cpp:712
  46:     0x55555b3a5b55 - Evaluate
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/jsapi.cpp:4407
  47:     0x55555b3a5e90 - Evaluate
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/jsapi.cpp:4443
  48:     0x55555b3a6410 - _ZN2JS8EvaluateEP9JSContextRKNS_22ReadOnlyCompileOptionsEPKDsmNS_13MutableHandleINS_5ValueEEE
                        at /home/mateon/.cargo/registry/src/github.com-1ecc6299db9ec823/mozjs_sys-0.50.0/mozjs/js/src/jsapi.cpp:4501
  49:     0x555557e7895d - script::dom::globalscope::GlobalScope::evaluate_script_on_global_with_result::{{closure}}::hc2c7d4ccb1ebf881
                        at components/script/dom/globalscope.rs:414
  50:     0x555557458930 - profile_traits::time::profile::hf0ef2260964ed4a4
                        at /shared/dev/rust/servo/components/profile_traits/time.rs:125
  51:     0x55555731788f - script::dom::globalscope::GlobalScope::evaluate_script_on_global_with_result::hc7ea15990d3a0937
                        at components/script/dom/globalscope.rs:398
  52:     0x555557e642b6 - script::dom::htmlscriptelement::HTMLScriptElement::run_a_classic_script::ha0e4d632ea02b992
                        at components/script/dom/htmlscriptelement.rs:569
  53:     0x555557e63c25 - script::dom::htmlscriptelement::HTMLScriptElement::execute::hff9b43b2271c3a80
                        at components/script/dom/htmlscriptelement.rs:539
  54:     0x555557e61f4e - script::dom::htmlscriptelement::HTMLScriptElement::prepare::h7c4c688807744c6f
                        at components/script/dom/htmlscriptelement.rs:452
  55:     0x55555783f95d - script::dom::servoparser::ServoParser::tokenize::h77a8946727767ec9
                        at components/script/dom/servoparser/mod.rs:473
  56:     0x555556eb0d27 - script::dom::servoparser::ServoParser::do_parse_sync::h6f827e51cedfced9
                        at components/script/dom/servoparser/mod.rs:428
  57:     0x55555783f2ef - script::dom::servoparser::ServoParser::parse_sync::{{closure}}::h1bc0bdcda668941a
                        at components/script/dom/servoparser/mod.rs:414
  58:     0x5555574583bc - profile_traits::time::profile::he12e778dcb1196f2
                        at /shared/dev/rust/servo/components/profile_traits/time.rs:125
  59:     0x555556eb0a8e - script::dom::servoparser::ServoParser::parse_sync::hd1cc34b5b0487f42
                        at components/script/dom/servoparser/mod.rs:411
  60:     0x555556eb0fdd - script::dom::servoparser::ServoParser::parse_bytes_chunk::h84269f40a9194091
                        at components/script/dom/servoparser/mod.rs:453
  61:     0x555556eb39e3 - <script::dom::servoparser::ParserContext as net_traits::FetchResponseListener>::process_response_chunk::h4adbcc96533d853d
                        at components/script/dom/servoparser/mod.rs:720
  62:     0x55555716ab4f - script::script_thread::ScriptThread::handle_fetch_chunk::h563f545d0ca052dd
                        at components/script/script_thread.rs:2542
  63:     0x555557155bb3 - script::script_thread::ScriptThread::handle_msg_from_constellation::h8cf45041f7282b8d
                        at components/script/script_thread.rs:1269
  64:     0x555557331f0c - script::script_thread::ScriptThread::handle_msgs::{{closure}}::h4683011b2bd13d1e
                        at components/script/script_thread.rs:1074
  65:     0x555557334cf5 - script::script_thread::ScriptThread::profile_event::hf584c39318e19a85
                        at components/script/script_thread.rs:1247
  66:     0x5555571529dd - script::script_thread::ScriptThread::handle_msgs::h565938d8050c7cb5
                        at components/script/script_thread.rs:1068
  67:     0x5555571506cb - script::script_thread::ScriptThread::start::h16d1bf289c232867
                        at components/script/script_thread.rs:900
  68:     0x55555732f6bc - <script::script_thread::ScriptThread as script_traits::ScriptThreadFactory>::create::{{closure}}::{{closure}}::hcedf169bd3fe885b
                        at components/script/script_thread.rs:581
  69:     0x555557c615c4 - profile_traits::mem::ProfilerChan::run_with_memory_reporting::he5ab23fe071cf439
                        at /shared/dev/rust/servo/components/profile_traits/mem.rs:63
  70:     0x55555732fc83 - <script::script_thread::ScriptThread as script_traits::ScriptThreadFactory>::create::{{closure}}::h9ef2c7ba5d36a96e
                        at components/script/script_thread.rs:580
  71:     0x555558648b74 - std::sys_common::backtrace::__rust_begin_short_backtrace::h953e62ce17b78fea
                        at /checkout/src/libstd/sys_common/backtrace.rs:133
  72:     0x55555824b55b - std::thread::Builder::spawn::{{closure}}::{{closure}}::h90781c0374be3f4e
                        at /checkout/src/libstd/thread/mod.rs:406
  73:     0x555557182784 - <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::h39af0b211967cbf1
                        at /checkout/src/libstd/panic.rs:293
  74:     0x555556cbb474 - std::panicking::try::do_call::h3439a98887008f1b
                        at /checkout/src/libstd/panicking.rs:479
  75:     0x55555bd58e7e - __rust_maybe_catch_panic
                        at libpanic_unwind/lib.rs:102
  76:     0x555556c6a5dc - std::panicking::try::hd11246e5dbe5c919
                        at /checkout/src/libstd/panicking.rs:458
  77:     0x5555571bc2bc - std::panic::catch_unwind::h1052347b62d11d3a
                        at /checkout/src/libstd/panic.rs:358
  78:     0x55555824ac98 - std::thread::Builder::spawn::{{closure}}::ha5d793ce774aea08
                        at /checkout/src/libstd/thread/mod.rs:405
  79:     0x55555824b775 - <F as alloc::boxed::FnBox<A>>::call_box::h68afeb10a2745593
                        at /checkout/src/liballoc/boxed.rs:788
  80:     0x55555bd43bbb - <alloc::boxed::Box<alloc::boxed::FnBox<A, Output$u3d$R$GT$$u20$$u2b$$u20$$u27$a$GT$$u20$as$u20$core..ops..function..FnOnce$LT$A$GT$$GT$::call_once::h13f1b0bf377a9f5b
                        at /checkout/src/liballoc/boxed.rs:798
                         - std::sys_common::thread::start_thread::hb5b6e0447b9691dc
                        at libstd/sys_common/thread.rs:24
                         - std::sys::unix::thread::Thread::new::thread_start::hcaff0bef1a01c624
                        at libstd/sys/unix/thread.rs:90
  81:     0x7ffff6eb0493 - start_thread
  82:     0x7ffff5479abe - __clone
  83:                0x0 - <unknown>
ERROR:servo: DomRefCell<T> already mutably borrowed: BorrowError
Pipeline failed in hard-fail mode.  Crashing!
Servo exited with return value 1

[jdm]

This is a result of #19872. cc @nox

[nox]

This is indeed a result of #19872 but it exhibits an existing bug where we seem to be mutably borrowing stuff while JS is running. I will look into it next week.

[dralley]

Bump

[jdm]

@dralley We appreciate help with issue triage, but "bump" comments aren't actionable.