monitor_info takes an extremely long time creating windows

[ColonelThirtyTwo]

Bevy version

0.15.1

[Optional] Relevant system information

Rust 1.84.1
Arch Linux
AMD Radeon RX 7800 XT (RADV NAVI32)
KDE Plasma (Wayland)

What you did

Run cargo run --example monitor_info on the 0.15.1 tag of bevy.

What went wrong

The windows for each monitor are only created after several minutes of waiting:

2025-02-02T02:03:21.079119Z TRACE wgpu_core::device::global: Device::create_compute_pipeline -> Id(3,1)    
2025-02-02T02:06:57.382343Z TRACE Poller::wait{timeout=None}:wait{epoll_fd=6 timeout=None}: polling::epoll: new events epoll_fd=6 res=1
2025-02-02T02:06:57.382565Z TRACE calloop::loop_logic: [calloop] Dispatching events for source #0    

After waiting, both windows (one for each monitor I have) spawn at the same time.

Additional information

Other examples create windows fine. Window mode nor transparency seems to matter.

Log with RUST_LOG=trace from monitor_info: monitor_info.txt

--features wayland does not seem to affect it.

[ColonelThirtyTwo]

Adding a primary window via the WindowPlugin seems to work around the issue - with that, the additional windows spawn in a timely manner.

[alice-i-cecile]

I suspect this is an OS-specific event loop bug, but I'd appreciate testing (from you or others) on alternate platforms.

[ColonelThirtyTwo]

Works fine on a Windows 11 laptop with an Nvidia RTX 4060 card running Vulkan.

I'll try running on a windows 10 installation of my desktop with the RTX card later, but I have a feeling it won't be different.

[ColonelThirtyTwo]

I suspect this is an OS-specific event loop bug, but I'd appreciate testing (from you or others) on alternate platforms.

Probably. According to rust-gdb, its stuck in the epoll_wait syscall:

#0  0x000055555793015f in rustix::backend::arch::asm::syscall4 (nr=..., a0=..., a1=..., a2=..., a3=...)
    at /home/col/.cargo/registry/src/index.crates.io-6f17d22bba15001f/rustix-0.38.44/src/backend/linux_raw/arch/x86_64.rs:154
#1  0x0000555557930e52 in rustix::backend::event::syscalls::epoll_wait (epfd=..., events=&mut [core::mem::maybe_uninit::MaybeUninit<rustix::event::epoll::Event>](size=1024) = {...}, timeout=-1)
    at /home/col/.cargo/registry/src/index.crates.io-6f17d22bba15001f/rustix-0.38.44/src/backend/linux_raw/arch/mod.rs:105
#2  0x000055555792f6be in rustix::event::epoll::wait<&std::os::fd::owned::OwnedFd> (epoll=0x55555c7b6cb0, event_list=0x55555c7c0e30, timeout=-1)
    at /home/col/.cargo/registry/src/index.crates.io-6f17d22bba15001f/rustix-0.38.44/src/event/epoll.rs:210
#3  0x0000555557935fc3 in polling::epoll::Poller::wait (self=0x55555c7b6cb0, events=0x55555c7c0e30, timeout=...) at src/epoll.rs:214
#4  0x00005555579324ba in polling::Poller::wait (self=0x55555c7b6cb0, events=0x55555c7c0e30, timeout=...) at src/lib.rs:744
#5  0x0000555557923968 in calloop::sys::Poll::poll (self=0x55555c7c0dd8, timeout=...) at src/sys.rs:233
#6  0x000055555768393c in calloop::loop_logic::EventLoop<winit::platform_impl::linux::x11::EventLoopState>::dispatch_events<winit::platform_impl::linux::x11::EventLoopState> (self=0x7fffffff8f20, timeout=..., 
    data=0x7fffffff8f59) at /home/col/.cargo/registry/src/index.crates.io-6f17d22bba15001f/calloop-0.13.0/src/loop_logic.rs:384
#7  0x0000555557686ee0 in calloop::loop_logic::EventLoop<winit::platform_impl::linux::x11::EventLoopState>::dispatch<winit::platform_impl::linux::x11::EventLoopState, core::option::Option<core::time::Duration>> (
    self=0x7fffffff8f20, timeout=..., data=0x7fffffff8f59) at /home/col/.cargo/registry/src/index.crates.io-6f17d22bba15001f/calloop-0.13.0/src/loop_logic.rs:559
#8  0x0000555557703899 in winit::platform_impl::linux::x11::EventLoop<bevy_winit::WakeUp>::poll_events_with_timeout<bevy_winit::WakeUp, &mut &mut winit::event_loop::{impl#6}::run_app::{closure_env#0}<bevy_winit::WakeUp, bevy_winit::state::WinitAppRunnerState<bevy_winit::WakeUp>>> (self=0x7fffffff8c18, timeout=..., callback=0x7fffffff8828)
    at /home/col/.cargo/registry/src/index.crates.io-6f17d22bba15001f/winit-0.30.8/src/platform_impl/linux/x11/mod.rs:468
#9  0x0000555557700eab in winit::platform_impl::linux::x11::EventLoop<bevy_winit::WakeUp>::pump_events<bevy_winit::WakeUp, &mut winit::event_loop::{impl#6}::run_app::{closure_env#0}<bevy_winit::WakeUp, bevy_winit::state::WinitAppRunnerState<bevy_winit::WakeUp>>> (self=0x7fffffff8c18, timeout=..., callback=0x7fffffff8a10)
    at /home/col/.cargo/registry/src/index.crates.io-6f17d22bba15001f/winit-0.30.8/src/platform_impl/linux/x11/mod.rs:424
#10 0x00005555577017b0 in winit::platform_impl::linux::x11::EventLoop<bevy_winit::WakeUp>::run_on_demand<bevy_winit::WakeUp, winit::event_loop::{impl#6}::run_app::{closure_env#0}<bevy_winit::WakeUp, bevy_winit::state::WinitAppRunnerState<bevy_winit::WakeUp>>> (self=0x7fffffff8c18, event_handler=...) at /home/col/.cargo/registry/src/index.crates.io-6f17d22bba15001f/winit-0.30.8/src/platform_impl/linux/x11/mod.rs:385
#11 0x00005555576feb81 in winit::platform_impl::linux::EventLoop<bevy_winit::WakeUp>::run_on_demand<bevy_winit::WakeUp, winit::event_loop::{impl#6}::run_app::{closure_env#0}<bevy_winit::WakeUp, bevy_winit::state::WinitAppRunnerState<bevy_winit::WakeUp>>> (self=0x7fffffff8c18, callback=...) at /home/col/.cargo/registry/src/index.crates.io-6f17d22bba15001f/winit-0.30.8/src/platform_impl/linux/mod.rs:819
#12 0x00005555576ff29e in winit::platform_impl::linux::EventLoop<bevy_winit::WakeUp>::run<bevy_winit::WakeUp, winit::event_loop::{impl#6}::run_app::{closure_env#0}<bevy_winit::WakeUp, bevy_winit::state::WinitAppRunnerState<bevy_winit::WakeUp>>> (self=..., callback=...) at /home/col/.cargo/registry/src/index.crates.io-6f17d22bba15001f/winit-0.30.8/src/platform_impl/linux/mod.rs:812
#13 0x00005555576dfff0 in winit::event_loop::EventLoop<bevy_winit::WakeUp>::run_app<bevy_winit::WakeUp, bevy_winit::state::WinitAppRunnerState<bevy_winit::WakeUp>> (self=..., app=0x7fffffff9748)
    at /home/col/.cargo/registry/src/index.crates.io-6f17d22bba15001f/winit-0.30.8/src/event_loop.rs:265
#14 0x00005555576ec7ff in bevy_winit::state::winit_runner<bevy_winit::WakeUp> (app=...) at crates/bevy_winit/src/state.rs:862
#15 0x00005555576a4410 in core::ops::function::FnOnce::call_once<fn(bevy_app::app::App) -> bevy_app::app::AppExit, (bevy_app::app::App)> ()
    at /home/col/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250
#16 0x00005555576a4122 in core::ops::function::FnOnce::call_once<fn(bevy_app::app::App) -> bevy_app::app::AppExit, (bevy_app::app::App)> ()
    at /home/col/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250
#17 0x000055555bce6729 in alloc::boxed::{impl#28}::call_once<(bevy_app::app::App), dyn core::ops::function::FnOnce<(bevy_app::app::App), Output=bevy_app::app::AppExit>, alloc::alloc::Global> (self=..., args=...)
    at /home/col/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/boxed.rs:1972
#18 0x000055555bd16fd5 in bevy_app::app::App::run (self=0x7fffffffd0c8) at crates/bevy_app/src/app.rs:170
#19 0x0000555557638bcf in monitor_info::main () at examples/window/monitor_info.rs:10

[alice-i-cecile]

Excellent investigation. Could you try reproducing with raw winit and opening a bug there, linking this one? I suspect we need to kick this up the dependency chain at least once.

[ColonelThirtyTwo]

Not easily. Seems like it's more complicated than simply creating a window in new_events or about_to_wait. I'm not familiar with what bevy is doing behind the scenes that may be contributing to this.