Minor fixes to await and await docs. (#555)

* Improved docs for await and related operations * Improved implementation of await * Fixed several test cases for invoke_waiting.
stlab · Jan 25, 2025 · d1016a8 · d1016a8
1 parent d80dacd
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diff --git a/CMakePresets.json b/CMakePresets.json
@@ -21,6 +21,19 @@
                 "stlab.coverage": "OFF"
             }
         },
+        {
+            "name": "debug-cpp20-tsan-ubsan-portable",
+            "description": "Ninja Debug Build",
+            "hidden": false,
+            "generator": "Ninja",
+            "binaryDir": "${sourceDir}/build/ninja-cpp20-debug-thread-undefined",
+            "cacheVariables": {
+                "CMAKE_CXX_STANDARD": "20",
+                "CMAKE_BUILD_TYPE": "DEBUG",
+                "STLAB_TASK_SYSTEM": "portable",
+                "CMAKE_CXX_FLAGS": "-fsanitize=thread -fsanitize=undefined"
+            }
+        },
         {
             "name": "ninja-cpp20-debug-thread-undefined",
             "description": "Ninja Debug Build",
@@ -30,8 +43,7 @@
             "cacheVariables": {
                 "CMAKE_CXX_STANDARD": "20",
                 "CMAKE_BUILD_TYPE": "DEBUG",
-                "CMAKE_CXX_FLAGS": "-fsanitize=thread -fsanitize=undefined",
-                "CMAKE_LINKER_FLAGS": "-fsanitize=thread -fsanitize=undefined"
+                "CMAKE_CXX_FLAGS": "-fsanitize=thread -fsanitize=undefined"
             }
         },
         {
@@ -45,6 +57,18 @@
                 "CMAKE_BUILD_TYPE": "DEBUG"
             }
         },
+        {
+            "name": "xcode-cpp20-debug-portable",
+            "description": "",
+            "hidden": false,
+            "generator": "Xcode",
+            "binaryDir": "${sourceDir}/build/xcode-cpp20-debug-portable",
+            "cacheVariables": {
+                "CMAKE_CXX_STANDARD": "20",
+                "CMAKE_BUILD_TYPE": "DEBUG",
+                "STLAB_TASK_SYSTEM": "portable"
+            }
+        },
         {
             "name": "ninja-cpp17-debug",
             "description": "Ninja Debug Build",

diff --git a/docs/README.md b/docs/README.md
@@ -1,54 +1,15 @@
 # `stlab` Documentation
 
-Pull requests for typos, examples, and other improvements are welcome. To file an issue, please use the [libraries repository](https://github.com/stlab/libraries).
-
-# Branch states
-
-\[ These are from the old site - FIX ME \]
-
-- **`master`:** [![master build](https://travis-ci.org/stlab/stlab.github.io.svg?branch=master)](https://travis-ci.org/stlab/stlab.github.io) [![master coverage](https://codecov.io/github/stlab/stlab.github.io/coverage.svg?branch=master)](https://codecov.io/gh/stlab/stlab.github.io/branch/master)
-
-- **`develop`:** [![develop build](https://travis-ci.org/stlab/stlab.github.io.svg?branch=develop)](https://travis-ci.org/stlab/stlab.github.io)
-  [![develop coverage](https://codecov.io/github/stlab/stlab.github.io/coverage.svg?branch=develop)](https://codecov.io/gh/stlab/stlab.github.io/branch/develop)
-
-# Building (Mac)
-
-You'll need Homebrew to make sure you have the most recent version of Ruby.
-
-## Setup
-
-1. Clone the repo
-2. `brew install ruby`
-3. `sudo gem install bundle jekyll github-pages liquid`
-
-Periodically run `gem update` and `bundle update` to make sure you have the latest jekyll tooling.
-
-## Building Docs
+This site is available at [stlab.cc](https://stlab.cc).
 
-```
-cd ./docs
-bundle exec jekyll serve --watch
-```
-
-Documentation viewable at `localhost:4000`
-Modifying sources should auto-regenerate the documentation
+Pull requests for typos, examples, and other improvements are welcome. To file an issue, please use the [libraries repository](https://github.com/stlab/libraries).
 
-## Building Examples
+## Building the Documentation
 
-1. `./build.sh` will download dependencies, build, and run all the `*.cpp` files in the `libraries` directory.
+To run a local Jekyll server, see the instructions in the docker-tools [README](../tools/docker-tools/README.md).
 
 ## Running Hyde in Docker
 
-The following directory structure is assumed.
-
-[ The longer term plan is to migrate the docs for the libraries into the library repo. We also need a plan for the structure of the build directory, a]
-
-```
-.             # This directory stlab.github.io
-../libraries  # The stlab/libraries repo
-../builds/hyde      # The cmake build directory configures for building docs
-```
-
 Configure the build as follows:
 
 ```
@@ -81,5 +42,6 @@ cd /mnt/host/libraries/docs
 ```
 
 \[ this is from the old docs - need to update the docs and script.
+
 > (or, simply `-u`) to generate the boilerplate for it. Then, fill in any fields marked as `__MISSING__`. Fields marked as `__OPTIONAL__` may be omitted.
-\]
+> \]
diff --git a/docs/include/stlab/algorithm/reverse.hpp/index.md b/docs/include/stlab/algorithm/reverse.hpp/index.md
@@ -3,7 +3,7 @@ layout: library
 title: stlab/algorithm/reverse.hpp
 hyde:
   owner: sean-parent
-  brief: __MISSING__
+  brief: A collection of algorithms for reversing sequences.
   tags:
     - sourcefile
   library-type: sourcefile

diff --git a/docs/include/stlab/concurrency/await.hpp/index.md b/docs/include/stlab/concurrency/await.hpp/index.md
@@ -3,7 +3,7 @@ layout: library
 title: stlab/concurrency/await.hpp
 hyde:
   owner: sean-parent
-  brief: "Await provides utilities to synchronously await the value from a `future` and to notify the default executor that a task is waiting. Blocking calls are discouraged because they may lead to deadlocks or thread explosions.\n\nThere is a good presentation of the issues [here](https://youtu.be/Z86b3Rd09sE).\n"
+  brief: "Await provides utilities to await the value from a `future<>` synchronously and to notify the default executor that a task is waiting. Blocking calls are discouraged because they may lead to deadlocks or thread explosions.\n\nThere is a good presentation of the issues [here](https://youtu.be/Z86b3Rd09sE).\n"
   tags:
     - sourcefile
   library-type: sourcefile

diff --git a/docs/tools/docker-tools/Dockerfile b/docs/tools/docker-tools/Dockerfile
@@ -5,17 +5,17 @@ FROM ubuntu:latest
 
 ARG DEBIAN_FRONTEND=noninteractive
 RUN apt-get update && apt-get install -y \
-    apt-utils \
-    fswatch \
-    g++ \
-    git \
-    libreadline-dev \
-    make \
-    nodejs \
-    npm \
-    rbenv \
-    wget \
-    zlib1g-dev
+  apt-utils \
+  fswatch \
+  g++ \
+  git \
+  libreadline-dev \
+  make \
+  nodejs \
+  npm \
+  rbenv \
+  wget \
+  zlib1g-dev
 
 RUN apt-get install -y libyaml-dev
 
@@ -26,9 +26,6 @@ RUN export N_USE_XZ=0; n latest
 RUN npm install -g npm@latest
 RUN npm install -g browser-sync
 
-###### Temporary #####
-RUN npm install -g sass-migrator
-
 # Create a user "app" so everything is not running at root
 RUN useradd -ms /bin/bash app
 USER app
@@ -47,12 +44,12 @@ RUN git clone https://github.com/rbenv/ruby-build.git "$(rbenv root)"/plugins/ru
 #  Install ruby
 ARG RUBY_VERSION
 RUN if [ -z ${RUBY_VERSION+x} ]; then \
-      rbenv install $(rbenv install -l | grep -v - | tail -1); \
-      rbenv global  $(rbenv install -l | grep -v - | tail -1); \
-    else \
-      rbenv install $RUBY_VERSION; \
-      rbenv global $RUBY_VERSION; \
-    fi
+  rbenv install $(rbenv install -l | grep -v - | tail -1); \
+  rbenv global  $(rbenv install -l | grep -v - | tail -1); \
+  else \
+  rbenv install $RUBY_VERSION; \
+  rbenv global $RUBY_VERSION; \
+  fi
 
 #  Install bundler in global ruby
 RUN (eval "$(rbenv init -)"; gem install bundler)
@@ -62,18 +59,6 @@ RUN (eval "$(rbenv init -)"; gem install bundler)
 USER app
 WORKDIR /home/app
 
-# RUN mkdir ./install
-# WORKDIR ./install
-# COPY ./docs/Gemfile .
-# COPY ./docs/Gemfile.lock .
-# COPY ./docs/.ruby-version .
-
-# RUN (eval "$(rbenv init -)"; \
-#     bundle config set frozen true; \
-#     bundle install)
-
-# WORKDIR /home/app
-
 EXPOSE 3000 3001
 
 # Add version file last to avoid cache invalidation for minor releases

diff --git a/docs/tools/docker-tools/README.md b/docs/tools/docker-tools/README.md
@@ -3,6 +3,7 @@
 ## Setup
 
 ### Install Docker
+
 If you don't already have Docker installed, [install Docker](https://docs.docker.com/get-docker/).
 
 ### Building the docker image

diff --git a/include/stlab/concurrency/await.hpp b/include/stlab/concurrency/await.hpp
@@ -36,20 +36,25 @@ inline namespace STLAB_VERSION_NAMESPACE() {
 /**************************************************************************************************/
 
 /**
-    Assumes f _will wait_ and wakes or adds a thread to the thread pool (to the limit) before
-    invoking f.
+    Assumes `f` _will wait_ and wakes or adds a thread to the thread pool (to the limit) before
+    invoking `f`. If using a condition variable, wrap the duration of the mutex lock in `f` to avoid
+    deadlocks.
 */
 template <class F>
 auto invoke_waiting(F&& f) {
 #if STLAB_TASK_SYSTEM(PORTABLE)
     if (!detail::pts().wake()) detail::pts().add_thread();
 #endif
 
-    std::forward<F>(f)();
+    return std::forward<F>(f)();
 }
 
 /**************************************************************************************************/
 
+/// Synchronously wait for the result `x`. If `x` resolves as an exception, the exception is
+/// rethrown. When using the portable task system, an additional thread is added to the pool if no
+/// threads are available and the maximum number of threads has not been reached.
+
 template <class T>
 auto await(future<T>&& x) -> T {
     if (x.is_ready()) return std::move(x).get_ready(); // if ready, done
@@ -65,35 +70,15 @@ auto await(future<T>&& x) -> T {
             condition.notify_one(); // must notify under lock
         }
     });
-
-#if STLAB_TASK_SYSTEM(PORTABLE)
-    if (!detail::pts().wake()) detail::pts().add_thread();
-
-    /*
-        If no tasks are available we wait for one tick of the system clock and exponentially
-        back off on the wait as long as no tasks are available.
-    */
-
-    for (auto backoff{std::chrono::steady_clock::duration{std::chrono::milliseconds{1}}}; true;
-         backoff *= 2) {
-        {
-            std::unique_lock<std::mutex> lock{m};
-            if (condition.wait_for(lock, backoff, [&] { return result.is_ready(); })) {
-                return std::move(result).get_ready();
-            }
-        }
-        detail::pts().wake(); // try to wake something to unstick.
-    }
-
-#else
-
-    std::unique_lock<std::mutex> lock{m};
-    condition.wait(lock, [&] { return result.is_ready(); });
+    invoke_waiting([&] {
+        std::unique_lock<std::mutex> lock{m};
+        condition.wait(lock, [&] { return result.is_ready(); });
+    });
     return std::move(result).get_ready();
-
-#endif
 }
 
+/// Equivalent to `await(copy(x))`.
+
 template <class T>
 [[deprecated("implicit copy deprecated, use `await(std::move(f))` or `await(stlab::copy(f))`"
              " instead.")]]
@@ -128,8 +113,10 @@ struct blocking_get_guarded {
     }
 
     auto wait_for(const std::chrono::nanoseconds& timeout) -> future<T> {
-        std::unique_lock<std::mutex> lock{_mutex};
-        _timed_out = !_condition.wait_for(lock, timeout, [&] { return _result.valid(); });
+        _timed_out = !invoke_waiting([&] {
+            std::unique_lock<std::mutex> lock{_mutex};
+            return _condition.wait_for(lock, timeout, [&] { return _result.valid(); });
+        });
         return _timed_out ? future<T>{} : std::move(_result);
     }
 };
@@ -140,10 +127,6 @@ template <class T>
 auto await_for(future<T>&& x, const std::chrono::nanoseconds& timeout) -> future<T> {
     if (x.is_ready()) return std::move(x);
 
-#if STLAB_TASK_SYSTEM(PORTABLE)
-    if (!detail::pts().wake()) detail::pts().add_thread();
-#endif
-
     auto p = std::make_shared<detail::blocking_get_guarded<T>>();
 
     auto hold = std::move(x).recover(immediate_executor, [_p = stlab::make_weak_ptr(p)](auto&& r) {
@@ -155,6 +138,8 @@ auto await_for(future<T>&& x, const std::chrono::nanoseconds& timeout) -> future
     return result.valid() ? std::move(result) : std::move(hold);
 }
 
+/// Equivalent to `await_for(copy(x), timeout)`.
+
 template <class T>
 [[deprecated("implicit copy deprecated, use `await_for(std::move(f), t)` or"
              " `await_for(stlab::copy(f), t)` instead.")]]

diff --git a/include/stlab/test/model.hpp b/include/stlab/test/model.hpp
@@ -18,6 +18,8 @@
 #include <iostream>
 #include <mutex>
 
+#include <stlab/concurrency/await.hpp>
+
 /**************************************************************************************************/
 
 namespace stlab {
@@ -41,9 +43,10 @@ struct annotate_counters {
     auto remaining() const -> std::size_t { return _copy_ctor + _move_ctor - _dtor + 1; }
 
     void wait(std::size_t count) {
-        std::unique_lock<std::mutex> lock(_mutex);
-        while (count != remaining())
-            _condition.wait(lock);
+        stlab::invoke_waiting([&] {
+            std::unique_lock<std::mutex> lock(_mutex);
+            _condition.wait(lock, [&] { return count == remaining(); });
+        });
     }
 
     friend inline auto operator<<(std::ostream& out, const annotate_counters& x) -> std::ostream& {