The majority of these are in comments, some in doc comments which might
affect the generated documentation, and a few in parameter names -
nothing that should be breaking, however.
- Hold the lock for a shorter amount of time
- Previously, when holding the lock while signaling, the other, resumed
thread could potentially get suspended again immediately because
the mutex was still locked.
- Fix comment
Previous implementation didn't check whether there are pending signals
after return from futex.wait. While it is ok for broadcast case it can
result in multiple wakeups when only one thread is signaled.
This implementation checks that there are pending signals before
returning from wait.
It is similar to the original implementation but the without initial
signal check, here we first go to the futex and then check for pending
signal.
fixes#12877
Current implementation (before this fix) observes number of waiters when
broadcast occurs and then makes that number of wakeups.
If we have multiple threads waiting for wakeup which immediately go into
wait if wakeup is not for that thread (as described in the issue). The
same thread can get multiple wakeups while some got none.
That is not consistent with documented behavior for condition variable
broadcast: `Unblocks all threads currently blocked in a call to wait()
or timedWait() with a given Mutex.`.
This fix ensures that the thread waiting on futext is woken up on futex wake.
* std: add Thread.Condition.timedWait
I needed the equivalent of `std::condition_variable::wait_for`, but it's missing in std.
This PR adds an implementation, following the status quo of using std.os.CLOCK.REALTIME in the pthread case (i.e. Futex)
A follow-up patch moving futex/condition stuff to monotonic clocks where available seems like a good idea.
This would involve conditionally exposing more functions and constants through std.c and std.os.
For instance, Chromium picks `pthread_cond_timedwait_relative_np` on macOS and `clock_gettime(CLOCK_MONOTONIC...)` on BSD's.
Tested on Windows 11, macOS 12.2.1 and Linux (with/without libc)
* Sleep in the single threaded case, handle timeout overflow in the Windows case and address a race condition in the AtomicCondition case.
This is a breaking change. Before, usage looked like this:
```zig
const held = mutex.acquire();
defer held.release();
```
Now it looks like this:
```zig
mutex.lock();
defer mutex.unlock();
```
The `Held` type was an idea to make mutexes slightly safer by making it
more difficult to forget to release an aquired lock. However, this
ultimately caused more problems than it solved, when any data structures
needed to store a held mutex. Simplify everything by reducing the API
down to the primitives: lock() and unlock().
Closes#8051Closes#8246Closes#10105
We already have a LICENSE file that covers the Zig Standard Library. We
no longer need to remind everyone that the license is MIT in every single
file.
Previously this was introduced to clarify the situation for a fork of
Zig that made Zig's LICENSE file harder to find, and replaced it with
their own license that required annual payments to their company.
However that fork now appears to be dead. So there is no need to
reinforce the copyright notice in every single file.
The primary purpose of this change is to eliminate one usage of
`usingnamespace` in the standard library - specifically the usage for
errno values in `std.os.linux`.
This is accomplished by truncating the `E` prefix from error values, and
making errno a proper enum.
A similar strategy can be used to eliminate some other `usingnamespace`
sites in the std lib.
- deprecates `std.Thread.spinLoopHint` and moves it to `std.atomic.spinLoopHint`
- added an Atomic(T) generic wrapper type which replaces atomic.Bool and atomic.Int
- in Atomic(T), selectively expose member functions depending on T and include bitwise atomic methods when T is an Integer
- added fence() and compilerFence() to std.atomic
* thread/condition: fix PthreadCondition compilation
* thread/condition: add wait, signal and broadcast
This is like std.Thread.Mutex which forwards calls to `impl`; avoids
having to call `cond.impl` every time.
* thread/condition: initialize the implementation
* move concurrency primitives that always operate on kernel threads to
the std.Thread namespace
* remove std.SpinLock. Nobody should use this in a non-freestanding
environment; the other primitives are always preferable. In
freestanding, it will be necessary to put custom spin logic in there,
so there are no use cases for a std lib version.
* move some std lib files to the top level fields convention
* add std.Thread.spinLoopHint
* add std.Thread.Condition
* add std.Thread.Semaphore
* new implementation of std.Thread.Mutex for Windows and non-pthreads Linux
* add std.Thread.RwLock
Implementations provided by @kprotty
