Summary:
Calling `EventBase::terminateLoopSoon` from a different thread should be a thread safe
operation when there is a concurrently executing `loopForever`, immediately
followed by `EventBase` destruction.

Today, we first set the stop_ flag to stop the event loop, then post a message to
tell eventlib to stop its event loop. ... but IIUC the stop_ flag is the thing
that makes the `while()` loop to keep going forever. Thus setting it before
message is posted may result in the `loopForever` terminate and underlying
EventBase destroyed before we are able to post a message to eventlib.

The fix is to set `stop_ = true` in loop.

Reviewed By: yfeldblum, andriigrynenko

Differential Revision: D29143212

fbshipit-source-id: f102fbad31653dd7525eff0f70600aa71ae02534

Summary: Rather than reinventing it in the test.

Reviewed By: markisaa

Differential Revision: D29223788

fbshipit-source-id: 3d35bd0046b876d22cd2397549dcb6f4cc77d688

Summary: Enabled the owner of AsyncUDPServerSocket to call setTimestamping for the underlying AsyncUDPSocket. So in the `onDataAvailable` callback we could have ts set in `OnDataAvailableParams`

Reviewed By: yfeldblum

Differential Revision: D28661584

fbshipit-source-id: d060cfdd8a4e105ada8a2c3b0fd13ddafb6f0d7c

Summary:
A new pattern which creates an invoker type and a variable, both named for the member, with the type suffixed with `_fn` and the instance unsuffixed. Applied to free-invokers, member-invokers, and static-member invokers.

Automatic mangling as this does is not great but this is intended to be used selectively.

Changes the existing unit-tests to use the invoker variables generated by the invoker-suite macros, since the invoker variables depend on the invoker types and the generation of both depends on the invoker macros. So everything gets tested transitively.

Reviewed By: luciang

Differential Revision: D29190157

fbshipit-source-id: 72d8fb622c4c99bae48efc3e5e9f0bd411d6a813

Summary: Use aliases. Reduce the use of the Atom template parameter.

Reviewed By: yfeldblum

Differential Revision: D29206490

fbshipit-source-id: d0637593c48ef150560b4feb47a454afe25ecba6

Summary:
`ASSERT_THAT` is defined in gmock, this adds the equivalent for coroutine code to GmockHelper.

The implementation depends on the inclusion of GtestHelper, but to avoid forcing anyone that includes GmockHelper to also include GtestHelper I didn't add it in the file.

Would it be preferable to include the needed header?

Reviewed By: yfeldblum

Differential Revision: D29067561

fbshipit-source-id: 26aa6021efe55aa03dd7cf064563a732e47e39a1

Summary:
An cross-platform abstraction layer for capturing current TCP and congestion control state.

Fetches information from four different resources:
- `TCP_INFO` (state of TCP)
- `TCP_CONGESTION` (name of congestion control algorithm)
- `TCP_CC_INFO` (details for a given congestion control algorithm)
- `SIOCOUTQ`/`SIOCINQ` (socket buffers)

`TcpInfo` is designed to solve two problems:

**(1) `TcpInfo` unblocks use of the latest `tcp_info` struct and related structs.**

As of 2020, the `tcp_info` struct shipped with glibc (sysdeps/gnu/netinet/tcp.h) has not been updated since 2007 due to compatibility concerns; see commit titled "Update netinet/tcp.h from Linux 4.18" in glibc repository. This creates scenarios where fields that have long been available in the kernel ABI cannot be accessed.

Even if glibc does eventually update the `tcp_info` shipped, we don't want to be limited to their update cycle. `TcpInfo` solves this in two ways:
   - First, `TcpInfoTypes.h` contains a copy of the latest `tcp_info` struct for Linux, and `TcpInfo` always uses this struct for lookups; this decouples `TcpInfo` from glibc's / the platform's `tcp_info`.
   - Second, `TcpInfo` determines which fields in the struct are populated (and thus valid) based on the number of bytes the kernel ABI copies into the struct during the corresponding getsockopt operation. When a field is accessed through `getFieldAsOptUInt64` or through an accessor, `TcpInfo` returns an empty optional if the field is unavailable at run-time.

In this manner, `TcpInfo` enables the latest struct to always be used while ensuring that programs can determine at runtime which fields are available for use --- there's no risk of a program assuming that a field is valid when it in fact was never initialized/set by the ABI.

**(2) `TcpInfo` abstracts platform differences while still keeping details available.**

The `tcp_info` structure varies significantly between Apple and Linux. `TcpInfo` exposes a subset of `tcp_info` and other fields through accessors that hide these differences, and reduce potential errors (e.g., Apple stores srtt in milliseconds, Linux stores in microseconds, `TcpInfo::srtt` does the conversions needed to always return in microseconds). When a field is unavailable on a platform, the accessor returns an empty optional.

In parallel, the underlying structures remain accessible and can be safely accessed through the appropriate `getFieldAsOptUInt64(...)`. This enables platform-specific code to have full access to the underlying structure while also benefiting from `TcpInfo`'s knowledge of whether a given field was populated by the ABI at run-time.

Support for FreeBSD will be added in a subsequent diff.

Differential Revision: D22134355

fbshipit-source-id: accae8762aa88c187cc473b8121df901c6ffb456

Summary:
The semicolons at the end of macros after `do {} while (0)` is useless and may cause potential compile errors in the future.

Pull Request resolved: https://github.com/facebook/folly/pull/1605

Reviewed By: Mizuchi

Differential Revision: D29109549

Pulled By: yfeldblum

fbshipit-source-id: 0c585b2db059bc5f53a31671b044a2b86a707359

Summary: Added set/get APIs to configure TOS for listener sockets. The setListenerTos() sets the TOS for the server sockets and all accepted connections are expected to inherit the same. These APIs would be used by higher layers (like thrift server) to set the TOS on the server socket.

Reviewed By: jmswen

Differential Revision: D28651968

fbshipit-source-id: 30f251970269155adbf5e88e1079096dbeceb216

Summary: `collectAny` does not compile when used with `Task`s that return move only objects

Reviewed By: yfeldblum

Differential Revision: D29137632

fbshipit-source-id: d8fd4f46d4c014c7492dcd2fb7fe84921db8aad0

Summary:
EventBase keeps a registry of EventBaseLocal instances.EventBaseLocal keeps a registry of EventBase instances.
At destruction time, both are trying to remove themselves from the other's registry, and it is possible that dtors are racing each other.

There are two changes to address the race:
1. remove virtual method in EventBaseLocal because calling through vptr makes TSAN unhappy - the underlying vtbl is being mutated during destruction.
2.  Since deregistration involves acquiring two locks, a lock inversion must be avoided. This is achieved by retrying if inner lock acquisition has failed.

Reviewed By: andriigrynenko

Differential Revision: D29120201

fbshipit-source-id: 93c93c8d7cc7126e3432ac06562d55a838008e4a

Summary: As title

Reviewed By: mzlee

Differential Revision: D29140913

fbshipit-source-id: 6a90756f1c340faaf9e857d743ccbeb1dc991b2f

Summary: Stub out sockets when building under EMSCRIPTEN (aka WASM compiler) like was done in D26579892 (https://github.com/facebook/folly/commit/c76b89b60652af52ee163795d526f2f10a114b20) for XROS.

Reviewed By: yfeldblum

Differential Revision: D28107594

fbshipit-source-id: 8a0d3033793a857cce587c5349934bc6f2a4bec5

Summary:
Copied TEST_P def from https://github.com/google/googletest/blob/master/googletest/include/gtest/gtest-param-test.h

Implemented `TestBody()` as `blockingWait(co_TestBody())`. User is responsible for delivering impl of `co_TestBody()`.

Reviewed By: yfeldblum

Differential Revision: D29124282

fbshipit-source-id: ca8e9b874903b84ab529e7eefa6a2b7f72793b9b

Reviewed By: chadaustin

Differential Revision: D29084022

fbshipit-source-id: 0605c1bfdd86ab94f4aa6893737b296ab4cdd913

Summary:
`collectAll` allows to `co_await`s multiple tasks using structured concurrency.

Unfortunately `future::collectAny` does not follow the structured concurrency pattern, and detaches the uncompleted operations.
This can result in memory errors (the coroutines access data that has already been freed).

This diff introduces `coro::collectAny`, which given a number of awaitables it returns the result of the first awaitable to finish, in addition to its index, cancels the remaining operations **and waits for them to complete**.

The implementation uses `collectAll` as a building block.
The return signature mirrors the one from `future::collectAny`.

Reviewed By: yfeldblum, rptynan

Differential Revision: D28945040

fbshipit-source-id: 402be03e004d373cbc74821ae8282b1aaf621b2d

Summary:
Similar to std::latch (C++20) but with timed waits:
https://en.cppreference.com/w/cpp/thread/latch

The latch class is a downward counter which can be used to synchronize
threads. The value of the counter is initialized on creation. Threads may
block on the latch until the counter is decremented to zero. There is no
possibility to increase or reset the counter, which makes the latch a
single-use barrier.

Example:

  const int N = 32;
  folly::Latch latch(N);
  std::vector<std::thread> threads;
  for (int i = 0; i < N; i++) {
    threads.emplace_back([&] {
      do_some_work();
      latch.count_down();
    });
  }
  latch.wait();

A latch can be used to easily wait for mocked async methods in tests:

  ACTION_P(DecrementLatchImpl, latch) {
    latch.count_down();
  }
  constexpr auto DecrementLatch = DecrementLatchImpl<folly::Latch&>;

  class MockableObject {
   public:
    MOCK_METHOD(void, someAsyncEvent, ());
  };

  TEST(TestSuite, TestFeature) {
    MockableObject mockObjA;
    MockableObject mockObjB;

    folly::Latch latch(5);

    EXPECT_CALL(mockObjA, someAsyncEvent())
        .Times(2)
        .WillRepeatedly(DecrementLatch(latch)); // called 2 times

    EXPECT_CALL(mockObjB, someAsyncEvent())
        .Times(3)
        .WillRepeatedly(DecrementLatch(latch)); // called 3 times

    // trigger async events
    // ...

    EXPECT_TRUE(latch.try_wait_for(std::chrono::seconds(60)));
  }

Reviewed By: yfeldblum

Differential Revision: D28951720

fbshipit-source-id: 6a9e20ad925a38d1cdb0134eedad826771bef3e0

Summary: `Synchronized` no longer needs a full lock-traits facility. Absorb the few things it needs and cut the rest.

Reviewed By: simpkins

Differential Revision: D28774648

fbshipit-source-id: 0679a3192a8eb17444628d12704cdc34fe5911b3

Summary: Now that `LockedPtr::as_lock` is always available regardless of mutex type and regardless of lock category, `getUniqueLock` is no longer needed.

Differential Revision: D28987941

fbshipit-source-id: a6894cffb30d280ec8325c14784592b2d4381f4c

Summary: The new name is `LockedPtr::as_lock`.

Reviewed By: aary

Differential Revision: D28987868

fbshipit-source-id: 8abd6a69a1b9c884adf137f06c24fe0df9ddd089

Summary: Pull Request resolved: https://github.com/facebook/folly/pull/1580

Reviewed By: luciang

Differential Revision: D28627136

Pulled By: yfeldblum

fbshipit-source-id: 1362506502ad3282f53512999d1c79822f2ce6e8

Differential Revision: D29089239

fbshipit-source-id: 83cbe9d74d8f7f648e18b8ce1e3e13ca8cb33006

Summary:
Use `std::unique_lock`, `std::shared_lock`, and `folly::upgrade_lock`. There are two reasons:

* Makes generic the use of `std::unique_lock` with `std::mutex`, which is currently special-cased.
* Permits specializations of `std::unique_lock` and the other lock types to be found automatically.

In particular, this permits the use of `Synchronized<T, DistributedMutex>`, which is only proxy-lockable and not lockable.

Reviewed By: simpkins

Differential Revision: D28705607

fbshipit-source-id: 48daa2910ce16ee4fde6f5ea629a41d9768f3c87

Summary: They were used as extension points at one time, but no longer.

Reviewed By: Alfus

Differential Revision: D28987212

fbshipit-source-id: e9d59e5cf9641323657314b088eef516ce068112

Summary:
```
auto x = std::atomic<std::uint64_t>{0};
auto y = std::atomic<std::uint64_t>{0};

// thread 1
x.store(1, std::memory_order_release);
auto one = y.load(std::memory_order_seq_cst);

// thread 2
y.fetch_add(1, std::memory_order_seq_cst);
auto two = x.load(std::memory_order_seq_cst);
```
Here it is possible for both `one` and `two` to end up with the value `0`. The
code in ParkingLot assumed that this would not be possible; and the counter used
to track the number of waiters could get reordered with respect to loads around
it.  This diff adds a seq_cst fence to ensure unparking threads always sequence
their stores before parking _before_ the counter load globally.

Reviewed By: yfeldblum, ot

Differential Revision: D28972810

fbshipit-source-id: 06eb6a2e6df6b00bf07ac8454a79257a5276e154

Summary: To observe how the compiler generates corresponding code.

Reviewed By: Alfus

Differential Revision: D28984027

fbshipit-source-id: d1c86197931aad257eb922cec9810c71ecdfc20a

Summary:
The numeric functions `less_than` and `greater_than` are intended for integer use but, technically, they are not constrained to integer use. If they are used with floating-point types, `min()` does not do the expected thing so use use `lowest()`.

Fixes: https://github.com/facebook/folly/issues/1604.

Reviewed By: iahs

Differential Revision: D29069620

fbshipit-source-id: 369bd59338b889cb1ec0f56d232a3775500573d0

Summary:
Ref: https://abseil.io/tips/143

Pull Request resolved: https://github.com/facebook/folly/pull/1603

Differential Revision: D29034248

Pulled By: yfeldblum

fbshipit-source-id: 87ae1970eab3f067d71a480fc7a95b18e2041c6d

Summary: Use the global immutable executor by default for SerialExecutor.

Reviewed By: yfeldblum

Differential Revision: D28925750

fbshipit-source-id: 91f75cfb3a4880098d933fe1f148d5c3b2e896e7

Summary:
Remove unused HazptrDomain data members unprotected_ and children_ and the function reclaim_unprotected_safe.

The data members and function were used before the change in October 2020 that eliminated the nesting of synchronous reclamation within asynchronous reclamation.

Reviewed By: yfeldblum

Differential Revision: D29017460

fbshipit-source-id: 645a61aedc801cb3eb14a4c3a085fea8b8422f1e

Summary: Remove all uses of the default SerialExecutor by changing callsites to be explicit, and removing the default parameter. This will allow us to change the default to a safer option in a subsequent diff.

Reviewed By: yfeldblum

Differential Revision: D28842180

fbshipit-source-id: 93027dcf8b19c44380534dabd731651780dac90e

Summary: io_uring SendmsgRecvmsg test fixes

Reviewed By: danobi

Differential Revision: D29003163

fbshipit-source-id: c1139a67d7b687d0eab21be7c6329f593dbe6ea9

Summary: A function like keep_sink but marked `noexcept`. Useful for shrinking check functions with duplicated cleanups.

Reviewed By: aary

Differential Revision: D28984340

fbshipit-source-id: f1099d43db25492db0e633f8cc8a5d44bcf157bc

Reviewed By: yfeldblum

Differential Revision: D28995271

fbshipit-source-id: bd64f4f98742fbad801f3db15a9cb8f5f71fe4b1

Summary:
The testpilot command line getdeps generated was not suitable for tpx
when filtering. tpx would consider the passed test filter an
environment variable.

Reorder a few things to at least make filtering work.

Reviewed By: fanzeyi

Differential Revision: D28976061

fbshipit-source-id: 21c45b3a4a59711a2a5da36a1bd11b7b4871ec5d

Summary:
Android NDK bionic with FORTIFY will override original `open()` definition and making folly `wrapNoInt` template failed to deduct.
The issue may happen only after NDK r21 because [this commit landed after r21](https://android.googlesource.com/platform/bionic/+/9349b9e51b41d12fd054b925802b626ca2db0afb%5E%21/#F0)

References:
https://github.com/android/ndk/issues/1328
https://github.com/llvm/llvm-project/commit/0a0e411204a2baa520fd73a8d69b664f98b428ba

Pull Request resolved: https://github.com/facebook/folly/pull/1593

Test Plan:
Tested running `objdump -dr` on the object file generated in both `mode/opt`
and `mode/opt-gcc` build modes and confirmed the generated code was
identical.

Reviewed By: yfeldblum

Differential Revision: D28953120

Pulled By: simpkins

fbshipit-source-id: 225583a5a011e8456592a0bcfcd669fe966ea6af

Summary: Introduces a CancellableAsyncScope type that automatically adds a CancellationToken to every task added() on the scope.

Reviewed By: yfeldblum

Differential Revision: D28438228

fbshipit-source-id: 2416725360c16f8d95dd5c35997dd624278d0980

Summary: Add a specialization of `folly::hasher<std::string_view>` parallel to the specialilzation of `folly::hasher<std::string>`.

Reviewed By: luciang

Differential Revision: D28921343

fbshipit-source-id: 77213d9ff66cec57b6d36b214c41e479e1d9455d

Summary: We need a thread-safe alternative to `LOG_FIRST_N(severity, n)` -- specifically when n = 1, the most common case.

Reviewed By: yfeldblum, ot, luciang

Differential Revision: D28884240

fbshipit-source-id: 41c937bf37dba036b71f1c62fd70445e79a3924a

Summary: Since we're moving towards enabling TLS 1.3 by default in folly, add this version to the SSLVersion enum.

Reviewed By: yfeldblum

Differential Revision: D28908538

fbshipit-source-id: 19d9ee248fff4682eec59c6f3d699fc6c9fa1917