100 CPU load and infinite loop

[giftal]

A lot of if-then-else compositions cause rust-analyzer to load CPU 100%.
A corner case .rs file attached that leads to rust analyzer crash.
Please add annotation for rust analyzer to avoid analysis of complicated functions (like the one attached). E.g. rust fmt has #[rustfmt::skip], maybe offer something like #[rustanalyzer::skip]

rust_code_example.zip

[flodiebold]

Is the file you provided the actual code? It's not even valid syntactically, since you can't make a variable named return. (Edit: Ok, the loop is actually in the parser, so this isn't so surprising.)

[giftal]

It is the actual code. Please rename the variable "return" to "ret" or whatever.

[giftal]

rust_code_example.zip

attached it the syntactically correct code. Please use it for tests.

[flodiebold]

Does the problem actually happen with the syntactically correct code?

[giftal]

Yes I confirm this! The problems always happens with the code that compiles successfully.
The one I attached 2nd time is correct as well.

[dignifiedquire]

Running into this as well. I was able to attach lldb to it and gather the following traces

git commit: 190a0595a478d059fdd95a179fe38d59cb6379be

Executable module set to "/Users/dignifiedquire/.cargo/bin/rust-analyzer".
Architecture set to: x86_64h-apple-macosx.
(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
  * frame #0: 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
    frame #1: 0x00007fff7f0ca56e libsystem_pthread.dylib`_pthread_cond_wait + 722
    frame #2: 0x0000000107269f12 rust-analyzer`std::thread::park::hde008ae05bf6ce2e [inlined] std::sys::unix::condvar::Condvar::wait::haf711209224495da at condvar.rs:73:17 [opt]
    frame #3: 0x0000000107269f0d rust-analyzer`std::thread::park::hde008ae05bf6ce2e [inlined] std::sys_common::condvar::Condvar::wait::hbda63240707accba at condvar.rs:50 [opt]
    frame #4: 0x0000000107269f0d rust-analyzer`std::thread::park::hde008ae05bf6ce2e [inlined] std::sync::condvar::Condvar::wait::h176016a76bad0c38 at condvar.rs:200 [opt]
    frame #5: 0x0000000107269ef3 rust-analyzer`std::thread::park::hde008ae05bf6ce2e at mod.rs:919 [opt]
    frame #6: 0x0000000107260785 rust-analyzer`crossbeam_channel::context::Context::wait_until::h4c4da7e476636502 + 325
    frame #7: 0x0000000107260415 rust-analyzer`crossbeam_channel::context::Context::with::_$u7b$$u7b$closure$u7d$$u7d$::h6657e7b32116da97 + 485
    frame #8: 0x0000000107260998 rust-analyzer`crossbeam_channel::select::run_select::h58f57381a0cf5b86 + 408
    frame #9: 0x00000001062caba8 rust-analyzer`rust_analyzer::main_loop::main_loop::h86d8e7a76e6b731a + 5096
    frame #10: 0x000000010614d881 rust-analyzer`rust_analyzer::main::hb300eef24b10a083 + 5921
    frame #11: 0x0000000106177326 rust-analyzer`std::rt::lang_start::_$u7b$$u7b$closure$u7d$$u7d$::h44458d503897e783 + 6
    frame #12: 0x000000010727a2d9 rust-analyzer`std::rt::lang_start_internal::h2d2d7c5f224149f7 [inlined] std::rt::lang_start_internal::_$u7b$$u7b$closure$u7d$$u7d$::hc4eba503b68bbb2b at rt.rs:52:13 [opt]
    frame #13: 0x000000010727a2ce rust-analyzer`std::rt::lang_start_internal::h2d2d7c5f224149f7 [inlined] std::panicking::try::do_call::h55672a70972b9078 at panicking.rs:297 [opt]
    frame #14: 0x000000010727a2ce rust-analyzer`std::rt::lang_start_internal::h2d2d7c5f224149f7 [inlined] std::panicking::try::h6d9221801de1cfe0 at panicking.rs:274 [opt]
    frame #15: 0x000000010727a2ce rust-analyzer`std::rt::lang_start_internal::h2d2d7c5f224149f7 [inlined] std::panic::catch_unwind::h382eeb03b10b2ef0 at panic.rs:394 [opt]
    frame #16: 0x000000010727a2ce rust-analyzer`std::rt::lang_start_internal::h2d2d7c5f224149f7 at rt.rs:51 [opt]
    frame #17: 0x000000010614e0f9 rust-analyzer`main + 41
    frame #18: 0x00007fff7eed33d5 libdyld.dylib`start + 1
(lldb) thread backtrace
* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
  * frame #0: 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
    frame #1: 0x00007fff7f0ca56e libsystem_pthread.dylib`_pthread_cond_wait + 722
    frame #2: 0x0000000107269f12 rust-analyzer`std::thread::park::hde008ae05bf6ce2e [inlined] std::sys::unix::condvar::Condvar::wait::haf711209224495da at condvar.rs:73:17 [opt]
    frame #3: 0x0000000107269f0d rust-analyzer`std::thread::park::hde008ae05bf6ce2e [inlined] std::sys_common::condvar::Condvar::wait::hbda63240707accba at condvar.rs:50 [opt]
    frame #4: 0x0000000107269f0d rust-analyzer`std::thread::park::hde008ae05bf6ce2e [inlined] std::sync::condvar::Condvar::wait::h176016a76bad0c38 at condvar.rs:200 [opt]
    frame #5: 0x0000000107269ef3 rust-analyzer`std::thread::park::hde008ae05bf6ce2e at mod.rs:919 [opt]
    frame #6: 0x0000000107260785 rust-analyzer`crossbeam_channel::context::Context::wait_until::h4c4da7e476636502 + 325
    frame #7: 0x0000000107260415 rust-analyzer`crossbeam_channel::context::Context::with::_$u7b$$u7b$closure$u7d$$u7d$::h6657e7b32116da97 + 485
    frame #8: 0x0000000107260998 rust-analyzer`crossbeam_channel::select::run_select::h58f57381a0cf5b86 + 408
    frame #9: 0x00000001062caba8 rust-analyzer`rust_analyzer::main_loop::main_loop::h86d8e7a76e6b731a + 5096
    frame #10: 0x000000010614d881 rust-analyzer`rust_analyzer::main::hb300eef24b10a083 + 5921
    frame #11: 0x0000000106177326 rust-analyzer`std::rt::lang_start::_$u7b$$u7b$closure$u7d$$u7d$::h44458d503897e783 + 6
    frame #12: 0x000000010727a2d9 rust-analyzer`std::rt::lang_start_internal::h2d2d7c5f224149f7 [inlined] std::rt::lang_start_internal::_$u7b$$u7b$closure$u7d$$u7d$::hc4eba503b68bbb2b at rt.rs:52:13 [opt]
    frame #13: 0x000000010727a2ce rust-analyzer`std::rt::lang_start_internal::h2d2d7c5f224149f7 [inlined] std::panicking::try::do_call::h55672a70972b9078 at panicking.rs:297 [opt]
    frame #14: 0x000000010727a2ce rust-analyzer`std::rt::lang_start_internal::h2d2d7c5f224149f7 [inlined] std::panicking::try::h6d9221801de1cfe0 at panicking.rs:274 [opt]
    frame #15: 0x000000010727a2ce rust-analyzer`std::rt::lang_start_internal::h2d2d7c5f224149f7 [inlined] std::panic::catch_unwind::h382eeb03b10b2ef0 at panic.rs:394 [opt]
    frame #16: 0x000000010727a2ce rust-analyzer`std::rt::lang_start_internal::h2d2d7c5f224149f7 at rt.rs:51 [opt]
    frame #17: 0x000000010614e0f9 rust-analyzer`main + 41
    frame #18: 0x00007fff7eed33d5 libdyld.dylib`start + 1
(lldb) threads
error: 'threads' is not a valid command.
(lldb) threads list
error: 'threads' is not a valid command.
(lldb) thread list
Process 18697 stopped
* thread #1: tid = 0x3a7c35, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
  thread #2: tid = 0x3a7c36, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #3: tid = 0x3a7c37, 0x00007fff7f009ef2 libsystem_kernel.dylib`read + 10
  thread #4: tid = 0x3a7c5a, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10, name = 'vfs'
  thread #5: tid = 0x3a7c5b, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #6: tid = 0x3a7c5c, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10, name = 'notify-convertor'
  thread #7: tid = 0x3a7c6b, 0x00007fff7f009bfe libsystem_kernel.dylib`__workq_kernreturn + 10
  thread #8: tid = 0x3a7d33, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #9: tid = 0x3a7d34, 0x00007fff7f00af06 libsystem_kernel.dylib`__psynch_mutexwait + 10
  thread #10: tid = 0x3a7d35, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #11: tid = 0x3a7d36, 0x00007fff7f00af06 libsystem_kernel.dylib`__psynch_mutexwait + 10
  thread #12: tid = 0x3a7d37, 0x00007fff7f00af06 libsystem_kernel.dylib`__psynch_mutexwait + 10
  thread #13: tid = 0x3a7d38, 0x00007fff7f00af06 libsystem_kernel.dylib`__psynch_mutexwait + 10
  thread #14: tid = 0x3a7d39, 0x00007fff7f00af06 libsystem_kernel.dylib`__psynch_mutexwait + 10
  thread #15: tid = 0x3a7d3a, 0x0000000107255e09 rust-analyzer`rowan::cursor::SyntaxNode::next_sibling_or_token::h7819dbb68e04663a + 25
  thread #16: tid = 0x3a7d3b, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #17: tid = 0x3a7d3c, 0x00007fff7f00af06 libsystem_kernel.dylib`__psynch_mutexwait + 10
  thread #18: tid = 0x3a7d3d, 0x00007fff7f00af06 libsystem_kernel.dylib`__psynch_mutexwait + 10
  thread #19: tid = 0x3a7d3e, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #20: tid = 0x3a7d3f, 0x00007fff7f00af06 libsystem_kernel.dylib`__psynch_mutexwait + 10
  thread #21: tid = 0x3a7d40, 0x00007fff7f00af06 libsystem_kernel.dylib`__psynch_mutexwait + 10
  thread #22: tid = 0x3a7d41, 0x00007fff7f00af06 libsystem_kernel.dylib`__psynch_mutexwait + 10
  thread #23: tid = 0x3a7d42, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #24: tid = 0x3a7d43, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #25: tid = 0x3a7d44, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #26: tid = 0x3a7d45, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #27: tid = 0x3a7d46, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #28: tid = 0x3a7d47, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #29: tid = 0x3a7d48, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #30: tid = 0x3a7d49, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #31: tid = 0x3a7d4a, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #32: tid = 0x3a7d4b, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #33: tid = 0x3a7d4d, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #34: tid = 0x3a7d4e, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #35: tid = 0x3a7d4f, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #36: tid = 0x3a7d50, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #37: tid = 0x3a7d51, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #38: tid = 0x3a7d52, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #39: tid = 0x3a7d53, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #40: tid = 0x3a7d54, 0x00007fff7f00b86a libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #41: tid = 0x3abb60, 0x00007fff7f00822a libsystem_kernel.dylib`mach_msg_trap + 10

[bjorn3]

What is the backtrace for thread #15: tid = 0x3a7d3a, 0x0000000107255e09 rust-analyzerrowan::cursor::SyntaxNode::next_sibling_or_token::h7819dbb68e04663a + 25`?

[giftal]

Folks, any update here or plans?

[giftal]

It got even worse these days. I put the code into external crate. But now rust-analyzer tries it's best and finds the crate ... Then kills my machine trying to analyze this

[lnicola]

There are a couple of performance and possibly crash issues in the parser, e.g. #5397, #5392 and some stack overflows I've noticed while fuzz testing. One potential improvement here would be changing the syntax tree representation, but that's still pending.

---

That said, your code sample is horrible and it's almost 13 MB (but that's not to say that the current performance is fine). This won't solve your problem, but at some point I've had the same idea for compiling decision trees into if-chains. I've never implemented it, but my gut feeling is that it's not worth blowing up the code size. Did you ever compare it to a more traditional (tree) implementation? This is only for my personal curiosity, of course.

[kdy1]

I hit this with a code generated by a proc-macro. I think there should be an option to opt-out or at least ignore code generated by proc-macros.

For context, I'm trying to use https://github.com/maciejhirsz/logos to make lexer faster.
logos creates lots of branches and lookup tables.

[lnicola]

@kdy1 there is an option, proc macro support is disabled by default.

[kdy1]

@lnicola I'm using default option, and items generated by proc macro does not show up in autocomplete. But cpu usage is 100%.

[lnicola]

Might be related to trait solving, there are a couple of open issues mentioning Diesel, for example.