trap on blocking call in sync task before return #12043
Conversation
dicej
force-pushed
the
trap-blocking-in-sync-tasks
branch
from
c6c26c4 to
3547452
Compare
github-actions
bot
added
the
wasmtime:api
|
Talked about this with @dicej today, current blockers are:
|
|
Regarding the Eventually, we'll want a proper way for host functions to "cheat" and block the whole guest without monopolizing the |
|
New thought: I think we're going to be required to implement "component-model-sync function can do async things on the host" in Wasmtime. Ignoring p3 for a moment, that's exactly how all async works in WASIp2. All WASIp2 functions are "sync" functions which leverage host superpowers to suspend the guest, and we can't break WASIp2, so I don't think that "just solve tcp/udp for wasip3" is a viable solution after all. |
dicej
force-pushed
the
trap-blocking-in-sync-tasks
branch
from
1dfed8a to
3d14cbf
Compare
Agreed, but I don't see how that's relevant to this PR. Sync-typed exports are still permitted to call sync-typed imports, and Certainly we'll need to confront p2 head-on once we remove or replace |
|
Er right, yes, wires crossed again. That means though that #12085 is possible which "fixes" tcp/udp. |
This implements a spec change (PR pending) such that tasks created for calls to
synchronous exports may not call potentially-blocking imports or return `wait`
or `poll` callback codes prior to returning a value. Specifically, the
following are prohibited in that scenario:
- returning callback-code.{wait,poll}
- sync calling an async import
- sync calling subtask.cancel
- sync calling {stream,future}.{read,write}
- sync calling {stream,future}.cancel-{read,write}
- calling waitable-set.{wait,poll}
- calling thread.suspend
This breaks a number of tests, which will be addressed in follow-up commits:
- The `{tcp,udp}-socket.bind` implementation in `wasmtime-wasi` is implemented
using `Linker::func_wrap_concurrent` and thus assumed to be async, whereas the
WIT interface says they're sync, leading to a type mismatch error at runtime.
Alex and I have discussed this and have a general plan to address it.
- A number of tests in the tests/component-model submodule that points to the
spec repo are failing. Those will presumably be fixed as part of the upcoming
spec PR (although some could be due to bugs in this implementation, in which
case I'll fix them).
- A number of tests in tests/misc_testsuite are failing. I'll address those in
a follow-up commit.
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
`check_blocking` needs access to the current task, but that's not set for post-return functions since those should not be calling _any_ imports at all, so first check for that. Signed-off-by: Joel Dice <joel.dice@fermyon.com>
This amounts to adding `async` to any exported component functions that might need to block. Signed-off-by: Joel Dice <joel.dice@fermyon.com>
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
Per the proposed spec changes, `thread.yield` should return control to the guest immediately without allowing any other thread to run. Similarly, when an async-lifted export or callback returns `CALLBACK_CODE_YIELD`, we should call the callback again immediately without allowing another thread to run. Signed-off-by: Joel Dice <joel.dice@fermyon.com>
dicej
force-pushed
the
trap-blocking-in-sync-tasks
branch
from
3d14cbf to
c3fb452
Compare
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
|
Some of the WAST tests are hanging and/or busy looping. I'll investigate this morning. |
This anticipates the forthcoming changes to WIT/CM async and helps us get CI green for bytecodealliance/wasmtime#12043 Signed-off-by: Joel Dice <joel.dice@fermyon.com>
Note that this temporarily updates the `tests/component-model` submodule to the branch for WebAssembly/component-model#577 until that PR is merged. Signed-off-by: Joel Dice <joel.dice@fermyon.com>
|
CI is green now; I'm temporarily pointing the |
|
I believe we're just waiting on a spec PR (hopefully accompanied by WAST tests covering the changes) at this point. |
2 participants
This implements a spec change (PR pending) such that tasks created for calls to synchronous exports may not call potentially-blocking imports or return
waitorpollcallback codes prior to returning a value. Specifically, the following are prohibited in that scenario:This breaks a number of tests, which will be addressed in follow-up commits:
TheEDIT: addressed by Relax required host capabilities in wasip3 tcp/udp bindings #12085{tcp,udp}-socket.bindimplementation inwasmtime-wasiis implemented usingLinker::func_wrap_concurrentand thus assumed to be async, whereas the WIT interface says they're sync, leading to a type mismatch error at runtime. Alex and I have discussed this and have a general plan to address it.A number of tests in the tests/component-model submodule that points to the spec repo are failing. Those will presumably be fixed as part of the upcoming spec PR (although some could be due to bugs in this implementation, in which case I'll fix them).
A number of tests in tests/misc_testsuite are failing. I'll address those in a follow-up commit.