Metal validation error with multisampling and multiple render passes?

[lordnoriyuki]

Following up on @kvark noticing a metal validation error in the other issue I filed.

-[MTLDebugRenderCommandEncoder validateFramebufferWithRenderPipelineState:], line 1288: error 'Framebuffer With Render Pipeline State Validation
For color attachment 0, the texture sample count (1) does not match the renderPipelineState colorSampleCount (4).
The sample count (1) does not match the renderPipelineState's sample count (4)

I created a small reproducible case, and the difference between this case and the MSAA line example (which doesn't trigger the metal validation error) is that the resolved target is not the swap chain frame, and I have a second render pass immediately following the multisample pass (that normally is drawing the resolved texture into the swap chain frame, but in this test case isn't actually doing anything).

In a nutshell, it's:

Create encoder
Begin render pass w/ attachment sample_count=4 texture and resolved_target sample_count =1 texture
Set pipeline on render pass where the pipeline has sample_count=4
Begin render pass w/ attachment swapchainframe.output.view and resolved_target None
Queue encoder.finish()

In the above, I'm not doing anything with the textures, setting vertex buffers, or drawing anything. I'm not even setting the pipeline on the second render pass.

Running it with METAL_DEVICE_WRAPPER_TYPE=1 fails with the metal validation error.

If I remove the second render pass (which isn't doing anything since I just begin it and drop it) then the metal validation error doesn't fire. It also fails on the 3rd frame rendered, which makes me think it's some internal state maintained by wgpu that's causing the problem here that's being triggered by multiple render passes.

multisample.zip

[lordnoriyuki]

Stack trace:

0   libsystem_kernel.dylib        	0x00007fff20304462 __pthread_kill + 10
1   libsystem_pthread.dylib       	0x00007fff20332610 pthread_kill + 263
2   libsystem_c.dylib             	0x00007fff20285720 abort + 120
3   libsystem_c.dylib             	0x00007fff202849d6 __assert_rtn + 314
4   com.apple.Metal               	0x00007fff2839afe4 MTLReportFailure.cold.1 + 43
5   com.apple.Metal               	0x00007fff283891b2 MTLReportFailure + 538
6   com.apple.Metal               	0x00007fff28382f6a _MTLMessageContextEnd + 987
7   com.apple.gpusw.MetalTools    	0x00007fff20aef2b4 -[MTLDebugRenderCommandEncoder validateFramebufferWithRenderPipelineState:] + 1137
8   com.apple.gpusw.MetalTools    	0x00007fff20aef4c6 -[MTLDebugRenderCommandEncoder setRenderPipelineState:] + 222
9   multisample                   	0x0000000109380895 _$LT$$LP$A$C$$RP$$u20$as$u20$objc..message..MessageArguments$GT$::invoke::h9b4bd79b80a91a0e + 101 (mod.rs:128)
10  multisample                   	0x0000000109357cc4 objc::message::platform::send_unverified::h5d1dc375bf040cc7 + 116 (mod.rs:27)
11  multisample                   	0x000000010935e30f objc::message::send_message::h24e5440c2834aa36 + 58 (mod.rs:178) [inlined]
12  multisample                   	0x000000010935e30f metal::encoder::RenderCommandEncoderRef::set_render_pipeline_state::hf8f670c5ad943290 + 367 (encoder.rs:196)
13  multisample                   	0x000000010928ba0f gfx_backend_metal::command::exec_render::h10a67c71fa7ae88b + 3087 (command.rs:1668)
14  multisample                   	0x0000000109289a78 gfx_backend_metal::command::PreRender::issue_many::he21b8da5c739f10c + 712 (command.rs:993)
15  multisample                   	0x00000001092918d7 _$LT$gfx_backend_metal..command..CommandBuffer$u20$as$u20$gfx_hal..command..CommandBuffer$LT$gfx_backend_metal..Backend$GT$$GT$::next_subpass::_$u7b$$u7b$closure$u7d$$u7d$::hf082e2487f20efad + 263 (command.rs:3488)
16  multisample                   	0x000000010933751f objc::rc::autorelease::autoreleasepool::hd58c6fa6099a1987 + 111 (autorelease.rs:29)
17  multisample                   	0x0000000109291754 _$LT$gfx_backend_metal..command..CommandBuffer$u20$as$u20$gfx_hal..command..CommandBuffer$LT$gfx_backend_metal..Backend$GT$$GT$::next_subpass::h0353ec0ca2045188 + 1076 (command.rs:3487)
18  multisample                   	0x0000000108e65624 _$LT$gfx_backend_metal..command..CommandBuffer$u20$as$u20$gfx_hal..command..CommandBuffer$LT$gfx_backend_metal..Backend$GT$$GT$::begin_render_pass::h9238fe57ffd194a8 + 2068 (command.rs:3452)
19  multisample                   	0x0000000108df8621 wgpu_core::command::render::_$LT$impl$u20$wgpu_core..hub..Global$LT$G$GT$$GT$::command_encoder_run_render_pass_impl::h0da57d700e55df83 + 17249 (render.rs:967)
20  multisample                   	0x0000000108df41e7 wgpu_core::command::render::_$LT$impl$u20$wgpu_core..hub..Global$LT$G$GT$$GT$::command_encoder_run_render_pass::hd7baadf00cb2cd36 + 167 (render.rs:435)
21  multisample                   	0x0000000108f8e138 _$LT$wgpu..backend..direct..Context$u20$as$u20$wgpu..Context$GT$::command_encoder_end_render_pass::h619aad289212b18e + 184 (direct.rs:1568)
22  multisample                   	0x0000000108f68d9b _$LT$wgpu..RenderPass$u20$as$u20$core..ops..drop..Drop$GT$::drop::h08eb53b45fe45b83 + 91 (lib.rs:2318)
23  multisample                   	0x0000000108cdf1f5 core::ptr::drop_in_place::h6738c34ba7857c14 + 21 (mod.rs:179)
24  multisample                   	0x0000000108d04b1c multisample::draw::he37d9e8c6ec3b044 + 1404 (main.rs:254)
25  multisample                   	0x0000000108cef632 multisample::main::_$u7b$$u7b$closure$u7d$$u7d$::h4b985772df717ee6 + 354 (main.rs:170)
26  multisample                   	0x0000000108cec597 _$LT$alloc..boxed..Box$LT$F$C$A$GT$$u20$as$u20$core..ops..function..FnMut$LT$Args$GT$$GT$::call_mut::ha5e8feb59f540f03 + 247 (boxed.rs:1325)
27  multisample                   	0x0000000108d021b6 _$LT$winit..platform_impl..platform..app_state..EventLoopHandler$LT$T$GT$$u20$as$u20$winit..platform_impl..platform..app_state..EventHandler$GT$::handle_nonuser_event::h612b71c94331274e + 246 (app_state.rs:71)
28  multisample                   	0x0000000108d6231e winit::platform_impl::platform::app_state::Handler::handle_nonuser_event::he6386776e192ce08 + 574 (app_state.rs:173)
29  multisample                   	0x0000000108d64147 winit::platform_impl::platform::app_state::AppState::cleared::hc2318257ccf47b2b + 1095 (app_state.rs:333)
30  multisample                   	0x0000000108d5da1e winit::platform_impl::platform::observer::control_flow_end_handler::h894663a27df52f29 + 78 (observer.rs:135)
31  com.apple.CoreFoundation      	0x00007fff20429d9d __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
32  com.apple.CoreFoundation      	0x00007fff20429c2d __CFRunLoopDoObservers + 549
33  com.apple.CoreFoundation      	0x00007fff20429211 __CFRunLoopRun + 1146
34  com.apple.CoreFoundation      	0x00007fff204286be CFRunLoopRunSpecific + 563
35  com.apple.HIToolbox           	0x00007fff28694fd0 RunCurrentEventLoopInMode + 292
36  com.apple.HIToolbox           	0x00007fff28694dcc ReceiveNextEventCommon + 709
37  com.apple.HIToolbox           	0x00007fff28694aef _BlockUntilNextEventMatchingListInModeWithFilter + 64
38  com.apple.AppKit              	0x00007fff22c41f85 _DPSNextEvent + 883
39  com.apple.AppKit              	0x00007fff22c4074b -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 1366
40  com.apple.AppKit              	0x00007fff22c32bda -[NSApplication run] + 586
41  multisample                   	0x0000000109450a06 _$LT$$LP$$RP$$u20$as$u20$objc..message..MessageArguments$GT$::invoke::h9450e3547d2d1221 + 70 (mod.rs:128)
42  multisample                   	0x0000000109450922 objc::message::platform::send_unverified::hff2723cd6ff29139 + 98 (mod.rs:27)
43  multisample                   	0x0000000108d02928 objc::message::send_message::hb286756e7e34ee4b + 27 (mod.rs:178) [inlined]
44  multisample                   	0x0000000108d02928 winit::platform_impl::platform::event_loop::EventLoop$LT$T$GT$::run_return::h1e511d15fa6ed3ff + 968 (event_loop.rs:106)
45  multisample                   	0x0000000108d02b34 winit::platform_impl::platform::event_loop::EventLoop$LT$T$GT$::run::hccf2cbce9110d701 + 84 (event_loop.rs:93)
46  multisample                   	0x0000000108cec403 winit::event_loop::EventLoop$LT$T$GT$::run::hc5a8ffe1d1f68e66 + 99 (event_loop.rs:154)
47  multisample                   	0x0000000108d04344 multisample::main::h509f33e5614ab3f6 + 3284 (main.rs:161)
48  multisample                   	0x0000000108cde7ce core::ops::function::FnOnce::call_once::h2a8b81ea8bae57c1 + 14 (function.rs:227)
49  multisample                   	0x0000000108d16661 std::sys_common::backtrace::__rust_begin_short_backtrace::h749a020585da00c2 + 17 (backtrace.rs:125)
50  multisample                   	0x0000000108d12324 std::rt::lang_start::_$u7b$$u7b$closure$u7d$$u7d$::ha793fc021c1872fa + 20 (rt.rs:66)
51  multisample                   	0x00000001097c9f84 core::ops::function::impls::_$LT$impl$u20$core..ops..function..FnOnce$LT$A$GT$$u20$for$u20$$RF$F$GT$::call_once::h4ab201f754b12ec0 + 7 (function.rs:259) [inlined]
52  multisample                   	0x00000001097c9f84 std::panicking::try::do_call::h2d40bab4a9c2dc4b + 7 (panicking.rs:379) [inlined]
53  multisample                   	0x00000001097c9f84 std::panicking::try::he14232182da07291 + 7 (panicking.rs:343) [inlined]
54  multisample                   	0x00000001097c9f84 std::panic::catch_unwind::ha032e0ba57e1000e + 7 (panic.rs:396) [inlined]
55  multisample                   	0x00000001097c9f84 std::rt::lang_start_internal::hebea83fb59fe572e + 644 (rt.rs:51)
56  multisample                   	0x0000000108d12301 std::rt::lang_start::h4038932d2736c529 + 65 (rt.rs:65)
57  multisample                   	0x0000000108d04c22 main + 34
58  libdyld.dylib                 	0x00007fff2034d631 start + 1

[kvark]

Thank you for filing! I believe this is an issue with gfx-backend-metal, and it's harmless.
I'm on it.

[kvark]

Fixed by gfx-backend-metal-0.6.5