1795311 - A new shmem class with more flexible lifetime management

Status: RESOLVED FIXED

(Core :: Graphics, task, P3)

Description

[Nicolas Silva [:nical]]

ipc::Shmem lifetime is managed by the IPDL actors that create them and as a result are automatically deallocated along with the actors, including during abnormal IPDL shutdown (other process crashes).

This aspect does not quite click with how some of the graphics code want to use shmem. In particular there are places where we "wrap" objects around the shared memory such as draw targets or WebGPU buffers. In these cases we want the possibility for the shmem to outlive IPDL actors and simply get deallocated when there is no more references to the shmem in the process.

Comment 1

[Nicolas Silva [:nical]]

Attachment: Bug 1795311 - A new shared memory class with more flexible memory management. r=nika,jld

Comment 2

[Nicolas Silva [:nical]]

Attachment: Bug 1795311 - Use the new shmem classes in the WebGPU buffer impl. r=jimb,jgilbert

Depends on D159398

Comment 3

[Nicolas Silva [:nical]]

TODO:

• Split the shmem class into the shmem mapping and the shmem handle.
• allocation returns a Maybe<std::pair<ShmemHandle, ShmemMapping>>
• move into the ipc namespace
• rename into one of "UnsafeShmem", "RawShmem", or "SharedMemoryMapping/SharedMemoryHandle"

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/60b9bfda2e8b
A new shared memory class with more flexible memory management. r=nika,jld
https://hg.mozilla.org/integration/autoland/rev/71697f876d88
Use the new shmem classes in the WebGPU buffer impl. r=jgilbert

Comment 5

[Cristian Tuns]

Backed out for causing build bustages on WebGPUParent.cpp

• Backout link
• Push with failures
• Failure Log
• Failure line: /builds/worker/fetches/sysroot-x86_64-linux-gnu/usr/include/c++/7/ext/new_allocator.h:136:4: error: use of deleted function 'mozilla::ipc::WritableSharedMemoryMapping::WritableSharedMemoryMapping(mozilla::ipc::WritableSharedMemoryMapping&&)'
  gmake[4]: *** [/builds/worker/checkouts/gecko/config/rules.mk:669: Unified_cpp_dom_webgpu0.o] Error 1
  /builds/worker/checkouts/gecko/dom/webgpu/ipc/WebGPUParent.cpp:367:70: error: use of deleted function 'mozilla::ipc::WritableSharedMemoryMapping::WritableSharedMemoryMapping(mozilla::ipc::WritableSharedMemoryMapping&&)'
  /builds/worker/checkouts/gecko/dom/webgpu/ipc/WebGPUParent.cpp:368:71: error: no matching function for call to 'std::unordered_map<long unsigned int, mozilla::webgpu::WebGPUParent::BufferMapData>::insert(std::pair<long unsigned int, mozilla::webgpu::WebGPUParent::BufferMapData>)'

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/3a19cc8f5a1e
A new shared memory class with more flexible memory management. r=nika,jld
https://hg.mozilla.org/integration/autoland/rev/57b736500aa2
Use the new shmem classes in the WebGPU buffer impl. r=jgilbert

Comment 7

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/3a19cc8f5a1e
https://hg.mozilla.org/mozilla-central/rev/57b736500aa2