Instead, use an enum to allow running both a procedure and sending the task
result over a channel. I expect the common case to be sending on a channel (e.g.
task::try), so don't require an extra allocation in the common case.
cc #11389
This, the Nth rewrite of channels, is not a rewrite of the core logic behind
channels, but rather their API usage. In the past, we had the distinction
between oneshot, stream, and shared channels, but the most recent rewrite
dropped oneshots in favor of streams and shared channels.
This distinction of stream vs shared has shown that it's not quite what we'd
like either, and this moves the `std::comm` module in the direction of "one
channel to rule them all". There now remains only one Chan and one Port.
This new channel is actually a hybrid oneshot/stream/shared channel under the
hood in order to optimize for the use cases in question. Additionally, this also
reduces the cognitive burden of having to choose between a Chan or a SharedChan
in an API.
My simple benchmarks show no reduction in efficiency over the existing channels
today, and a 3x improvement in the oneshot case. I sadly don't have a
pre-last-rewrite compiler to test out the old old oneshots, but I would imagine
that the performance is comparable, but slightly slower (due to atomic reference
counting).
This commit also brings the bonus bugfix to channels that the pending queue of
messages are all dropped when a Port disappears rather then when both the Port
and the Chan disappear.
Declare a `type SendStr = MaybeOwned<'static>` to ease readibility of
types that needed the old SendStr behavior.
Implement all the traits for MaybeOwned that SendStr used to implement.
* All I/O now returns IoResult<T> = Result<T, IoError>
* All formatting traits now return fmt::Result = IoResult<()>
* The if_ok!() macro was added to libstd
This will allow capturing of common things like logging messages, stdout prints
(using stdio println), and failure messages (printed to stderr). Any new prints
added to libstd should be funneled through these task handles to allow capture
as well.
Additionally, this commit redirects logging back through a `Logger` trait so the
log level can be usefully consumed by an arbitrary logger.
This commit also introduces methods to set the task-local stdout handles:
* std::io::stdio::set_stdout
* std::io::stdio::set_stderr
* std::io::logging::set_logger
These methods all return the previous logger just in case it needs to be used
for inspection.
I plan on using this infrastructure for extra::test soon, but we don't quite
have the primitives that I'd like to use for it, so it doesn't migrate
extra::test at this time.
Closes#6369
This will allow capturing of common things like logging messages, stdout prints
(using stdio println), and failure messages (printed to stderr). Any new prints
added to libstd should be funneled through these task handles to allow capture
as well.
Additionally, this commit redirects logging back through a `Logger` trait so the
log level can be usefully consumed by an arbitrary logger.
This commit also introduces methods to set the task-local stdout handles:
* std::io::stdio::set_stdout
* std::io::stdio::set_stderr
* std::io::logging::set_logger
These methods all return the previous logger just in case it needs to be used
for inspection.
I plan on using this infrastructure for extra::test soon, but we don't quite
have the primitives that I'd like to use for it, so it doesn't migrate
extra::test at this time.
Closes#6369
For libgreen, bookeeping should not be global but rather on a per-pool basis.
Inside libnative, it's known that there must be a global counter with a
mutex/cvar.
The benefit of taking this strategy is to remove this functionality from libstd
to allow fine-grained control of it through libnative/libgreen. Notably, helper
threads in libnative can manually decrement the global count so they don't count
towards the global count of threads. Also, the shutdown process of *all* sched
pools is now dependent on the number of tasks in the pool being 0 rather than
this only being a hardcoded solution for the initial sched pool in libgreen.
This involved adding a Local::try_take() method on the Local trait in order for
the channel wakeup to work inside of libgreen. The channel send was happening
from a SchedTask when there is no Task available in TLS, and now this is
possible to work (remote wakeups are always possible, just a little slower).
* vec::raw::to_ptr is gone
* Pausible => Pausable
* Removing @
* Calling the main task "<main>"
* Removing unused imports
* Removing unused mut
* Bringing some libextra tests up to date
* Allowing compiletest to work at stage0
* Fixing the bootstrap-from-c rmake tests
* assert => rtassert in a few cases
* printing to stderr instead of stdout in fail!()
There was a race in the code previously where schedulers would *immediately*
shut down after spawning the main task (because the global task count would
still be 0). This fixes the logic by blocking the sched pool task in receving on
a port instead of spawning a task into the pool to receive on a port.
The modifications necessary were to have a "simple task" running by the time the
code is executing, but this is a simple enough thing to implement and I forsee
this being necessary to have implemented in the future anyway.
Note that this removes a number of run-pass tests which are exercising behavior
of the old runtime. This functionality no longer exists and is thoroughly tested
inside of libgreen and libnative. There isn't really the notion of "starting the
runtime" any more. The major notion now is "bootstrapping the initial task".
The scheduler pool now has a much more simplified interface. There is now a
clear distinction between creating the pool and then interacting the pool. When
a pool is created, all schedulers are not active, and only later if a spawn is
done does activity occur.
There are four operations that you can do on a pool:
1. Create a new pool. The only argument to this function is the configuration
for the scheduler pool. Currently the only configuration parameter is the
number of threads to initially spawn.
2. Spawn a task into this pool. This takes a procedure and task configuration
options and spawns a new task into the pool of schedulers.
3. Spawn a new scheduler into the pool. This will return a handle on which to
communicate with the scheduler in order to do something like a pinned task.
4. Shut down the scheduler pool. This will consume the scheduler pool, request
all of the schedulers to shut down, and then wait on all the scheduler
threads. Currently this will block the invoking OS thread, but I plan on
making 'Thread::join' not a thread-blocking call.
These operations can be used to encode all current usage of M:N schedulers, as
well as providing a simple interface through which a pool can be modified. There
is currently no way to remove a scheduler from a pool of scheduler, as there's
no way to guarantee that a scheduler has exited. This may be added in the
future, however (as necessary).
This extracts everything related to green scheduling from libstd and introduces
a new libgreen crate. This mostly involves deleting most of std::rt and moving
it to libgreen.
Along with the movement of code, this commit rearchitects many functions in the
scheduler in order to adapt to the fact that Local::take now *only* works on a
Task, not a scheduler. This mostly just involved threading the current green
task through in a few locations, but there were one or two spots where things
got hairy.
There are a few repercussions of this commit:
* tube/rc have been removed (the runtime implementation of rc)
* There is no longer a "single threaded" spawning mode for tasks. This is now
encompassed by 1:1 scheduling + communication. Convenience methods have been
introduced that are specific to libgreen to assist in the spawning of pools of
schedulers.
* Streams are now ~3x faster than before (fewer allocations and more optimized)
* Based on a single-producer single-consumer lock-free queue that doesn't
always have to allocate on every send.
* Blocking via mutexes/cond vars outside the runtime
* Streams work in/out of the runtime seamlessly
* Select now works in/out of the runtime seamlessly
* Streams will now fail!() on send() if the other end has hung up
* try_send() will not fail
* PortOne/ChanOne removed
* SharedPort removed
* MegaPipe removed
* Generic select removed (only one kind of port now)
* API redesign
* try_recv == never block
* recv_opt == block, don't fail
* iter() == Iterator<T> for Port<T>
* removed peek
* Type::new
* Removed rt::comm
In order to keep up to date with changes to the libraries that `llvm-config`
spits out, the dependencies to the LLVM are a dynamically generated rust file.
This file is now automatically updated whenever LLVM is updated to get kept
up-to-date.
At the same time, this cleans out some old cruft which isn't necessary in the
makefiles in terms of dependencies.
Closes#10745Closes#10744
Right now, as pointed out in #8132, it is very easy to introduce a subtle race
in the runtime. I believe that this is the cause of the current flakiness on the
bots.
I have taken the last idea mentioned in that issue which is to use a lock around
descheduling and context switching in order to solve this race.
Closes#8132
The reasons for doing this are:
* The model on which linked failure is based is inherently complex
* The implementation is also very complex, and there are few remaining who
fully understand the implementation
* There are existing race conditions in the core context switching function of
the scheduler, and possibly others.
* It's unclear whether this model of linked failure maps well to a 1:1 threading
model
Linked failure is often a desired aspect of tasks, but we would like to take a
much more conservative approach in re-implementing linked failure if at all.
Closes#8674Closes#8318Closes#8863
These two attributes are no longer useful now that Rust has decided to leave
segmented stacks behind. It is assumed that the rust task's stack is always
large enough to make an FFI call (due to the stack being very large).
There's always the case of stack overflow, however, to consider. This does not
change the behavior of stack overflow in Rust. This is still normally triggered
by the __morestack function and aborts the whole process.
C stack overflow will continue to corrupt the stack, however (as it did before
this commit as well). The future improvement of a guard page at the end of every
rust stack is still unimplemented and is intended to be the mechanism through
which we attempt to detect C stack overflow.
Closes#8822Closes#10155
Now that the type_id intrinsic is working across crates, all of these
unnecessary messages can be removed to have the failure type for a task truly be
~Any and only ~Any
- `begin_unwind` is now generic over any `T: Any + Send`.
- Every value you fail with gets boxed as an `~Any`.
- Because of implementation details, `&'static str` and `~str` are still
handled specially behind the scenes.
- Changed the big macro source string in libsyntax to a raw string
literal, and enabled doc comments there.
Some code cleanup, sorting of import blocks
Removed std::unstable::UnsafeArc's use of Either
Added run-fail tests for the new FailWithCause impls
Changed future_result and try to return Result<(), ~Any>.
- Internally, there is an enum of possible fail messages passend around.
- In case of linked failure or a string message, the ~Any gets
lazyly allocated in future_results recv method.
- For that, future result now returns a wrapper around a Port.
- Moved and renamed task::TaskResult into rt::task::UnwindResult
and made it an internal enum.
- Introduced a replacement typedef `type TaskResult = Result<(), ~Any>`.
