* tests: handle spurious EWOULDBLOCK in io_async_fd
## Motivation
The `io_async_fd.rs` tests contain a `drain()` function, which
currently performs synchronous reads from a UDS socket until it returns
`io::ErrorKind::WouldBlock` (i.e., errno `EWOULDBLOCK`/`EAGAIN`). The
*intent* behind this function is to ensure that all data has been
drained from the UDS socket's buffer...which is what it appears to
do...on Linux. On other systems, it appears that an `EWOULDBLOCK` or
`EAGAIN` may be returned before enough data has been read from the UDS
socket to result in the other end being notified that the socket is now
writable. In particular, this appears to be the case on illumos, where
the tests using this function hang forever (see [this comment][1] on PR
#6769).
To my knowledge, this behavior is still POSIX-compliant --- the
reader will still be notified that the socket is readable, and if it
were actually doing non-blocking IO, it would continue reading upon
receipt of that notification. So, relying on `EWOULDBLOCK` to indicate
that the socket has been sufficiently drained appears to rely on
Linux/FreeBSD behavior that isn't necessarily portable to other Unices.
## Solution
This commit changes the `drain()` function to take an argument for the
number of bytes *written* to the socket previously, and continue looping
until it has read that many bytes, regardless of whether `EWOULDBLOCK`
is returned. This should ensure that the socket is drained on all
POSIX-compliant systems, and indeed, the `io_async_fd::reset_writable`
and `io_async_fd::poll_fns` tests no longer hang forever on illumos.
I think making this change is an appropriate solution to the
test failure here, as the `drain()` function is part of the test, rather
than the code in Tokio *being* tested, and (as I mentioned above) the
use of blocking reads on a non-blocking socket without a mechanism to
continue reading when the socket becomes readable again is not really
something a real life program seems likely to do. Ensuring that all the
written bytes have been read by passing in a byte count seems more
faithful to what the test is actually *trying* to do here, anyway.
Thanks to @jclulow for debugging what was going on here!
This change was cherry-picked from commit
f18d6ed7d4e0724bbe14db5519d7c80b3227a1a9 from PR #6769, so that the fix
can be merged separately.
[1]: https://github.com/tokio-rs/tokio/pull/6769#issuecomment-2284753794
Signed-off-by: Eliza Weisman <eliza@elizas.website>
## Motivation
As described in #6763, Tokio compiles for the [illumos] operating
system, but we don't presently have automated tests on illumos. We would
like to add illumos CI jobs for Tokio using [Buildomat], a CI system
which supports illumos. Buildomat CI jobs for Tokio will run on
infrastructure contributed by Oxide Computer Company.
In order for Buildomat to watch for commits to the repo, we must first
add a configuration file in `.github/buildomat/config.toml` with the
`enable = true` key. This config file must be present on the repo's main
branch for Buildomat to enable builds for the repo. See [here] for
details.
## Solution
This branch adds a `.github/buildomat` directory containing a config
file and a README summarizing what the configs in that directory are
for, as well as documenting how to get help diagnosing illumos CI
failures.
This branch does *not* add scripts for actually running CI jobs on
Buildomat. Since the config file must be present on the repo's main
branch before Buildomat runs CI jobs for the repo, I'd like to merge the
config file separately from the actual build scripts. This way, I can
actually have the build jobs run on the PR that adds them, making it
easier to ensure everything is working correctly before merging.
Closes#6766, which is obsoleted by this branch.
[illumos]: https://www.illumos.org/
[Buildomat]: https://github.com/oxidecomputer/
[here]:
https://github.com/oxidecomputer/buildomat/blob/main/README.md#per-repository-configuration
When instrumenting resources in Tokio, a span is created for each
resource. Previously, all resources inherited the currently active span
as their parent (tracing default). However, this would keep that parent
span alive until the resource (and its span) were dropped. This is often
not correct, as a resource may be created in a task and then sent
elsewhere, while the originating task ends.
This artificial extension of the parent span's lifetime would make it
look like that task was still alive (but idle) in any system reading the
tracing instrumentation in Tokio, for example Tokio Console as reported
in tokio-rs/console#345.
In #6107, most of the existing resource spans were updated to
make them explicit roots, so they have no contextual parent. However,
2. were missed:
- `Sleep`
- `BatchSemaphore`
This change alters the resource spans for those 2 resources to also make
them explicit roots.
To enable unstable features in Tokio, passing `--cfg tokio_unstable` to
the compiler is necessary. We document how to do this in a variety of
ways in the main Tokio (lib.rs) documentation.
One way is to add a `[build]` section to the file `.cargo/config.toml`.
Even though this filename is stated in the documentation, it is quite
common that first time users (including this author, some time ago) put
it in their `Cargo.toml` file instead.
This change adds a "warning" section to the documentation to reiterate
the point that this section doesn't go in the cargo manifest
(`Cargo.toml`).
On my machine, any test that calls `is_pidfd_available` fails as my
kernel string does not contain a '-'; the code expects there to be one.
Fix the test so that is works regardless on whether the kernel string
contains a '-'.
