Summary:
Original commit changeset: c6f013565680

Redo D22417488 (https://github.com/facebook/folly/commit/43d80f110b181dd7f72f0f935322a58f9cbb5147), with D22577887 fixing open source CI builds

Reviewed By: wez

Differential Revision: D22577884

fbshipit-source-id: 0c94483e05715493859d29bc2b58f0847a95826b

Summary:
The upstream [liburing](https://git.kernel.dk/cgit/liburing/tree/src/include/liburing.h) has changed to use ```extern "C" ```, we must remove the duplicated `extern "C"`.

Pull Request resolved: https://github.com/facebook/folly/pull/1416

Differential Revision: D22752570

Pulled By: yfeldblum

fbshipit-source-id: fa62d8e462e04676af6d563225455400d7e83c4b

Summary:
- OpenR building has been broken for quite awhile and it seems this is the main cause

Example CI Failure: https://github.com/facebook/openr/runs/631232675?check_suite_focus=true

Reviewed By: wez

Differential Revision: D22737174

fbshipit-source-id: 31d44c36d495295d30fe3ddc81991dafed100703

Summary: We should also use saturation detector on queues fronting CPUThreadPoolExecutor.

Reviewed By: andriigrynenko

Differential Revision: D20873689

fbshipit-source-id: 25ffc4cf62ddb222ede4f983f88a1c6545a0d4a5

Summary: The pthread_create redefinition also overrides the TSAN-specific pthread_create. This diff deletes this test because the test itself is of little value - see discussion in this diff.

Reviewed By: yfeldblum

Differential Revision: D22735273

fbshipit-source-id: a23089654697b85698f226b1110af3ed1a0b7fce

Summary: The test forgot to join the pthread.

Reviewed By: yfeldblum

Differential Revision: D22743458

fbshipit-source-id: 02231ce1e915b9f8679378eaf2ec18dc5dd67280

Summary:
Add some coroutine-native versions of the retrying algorithms available
for retrying folly::Future-based operations.

Adds the following:
* `retryWhen()` - This is the fundamental retry algorithm that allows
  you to specify logic to determine whether to retry and if so when to
  retry.
* `retryN()` - For simple use-cases that immediately retries operations
  up to N times.
* `retryWithExponentialBackoff()` - Retries the operation after an
   exponentially increasing delay with some random jitter applied.

Reviewed By: yfeldblum

Differential Revision: D22535487

fbshipit-source-id: c5594d0edfc2414015c345bee79e34f5cdafb789

Summary:
Building Folly on Fedora 32 fails with a link error, saying
SingletonVault::kDefaultShutdownTimeout_ is undefined. I did not
investigate, but this constant is only used in one place, so inline
it.

Reviewed By: yfeldblum

Differential Revision: D22713828

fbshipit-source-id: 707797eaef4633e642d07b2b02d9f55187afb99f

Summary:
This algorithm takes an awaitable and a duration and
cancels the operation and completes with a `FutureTimeout`
error if the operation does not complete within the specified
duration.

This differs from `timed_wait()` in that it still waits
for the child operation to complete, even once the timeout
has elapsed, rather than just detaching from the
operation and letting it complete in the background.

This relies on the operation responding to cancellation
in a timely manner for the algorithm to have the effect
of returning shortly after the timeout elapses.

The benefit of waiting for the child operation to complete,
however, is that it allows you to safely pass parameters by
reference to the child operation and be safe in knowing that
the child operation will complete before the awaiting
coroutine resumes and potentially destroys those parameters.

Reviewed By: yfeldblum

Differential Revision: D22199932

fbshipit-source-id: 4f6295a23a860ec52b639eb56a02f8029ffb9009

Summary: Basic FIFO queues observation hooks.

Reviewed By: andriigrynenko

Differential Revision: D20773870

fbshipit-source-id: 3f9cbab1b8b10204139ce153d92e08ffb5f6254c

Summary:
The `F14*Fallback.h` headers are meant to be included textually
from `F14*.h` headers and currently fail to compile in modular
builds, as a) they have references to items defined in their intended
enclosing header and b) even if successfully compiled alone would
provide conflicting definitions of the `F14*` structures.

This diff adds the `FOLLY_F14_VECTOR_INTRINSICS_AVAILABLE`
gate in the `F14*Fallback.h` headers so that they won't get compiled
when they're not used.

Reviewed By: yfeldblum, luciang

Differential Revision: D22568097

fbshipit-source-id: a75b3a4a687e3034dd9c4c3f7fd0a41bfd465272

Reviewed By: luciang

Differential Revision: D22555074

fbshipit-source-id: b853730e5d0dd96b6f94d71e2332653a1a44c9a1

Summary: Some build environments will complain that there is no return specified for the two modified functions despite the `CHECK(false)`. Switching to `folly::terminate_with` resolves.

Differential Revision: D22659960

fbshipit-source-id: cff7dd1366fab5c2530584b1f57821bc26b672d4

Summary: [Folly] Move `makeAsyncTask` test helpers inline into the test.

Reviewed By: ericniebler

Differential Revision: D22674219

fbshipit-source-id: 630c84ce153ad2bfb92d38f3d2c955cb3f043799

Summary: (Note: this ignores all push blocking failures!)

Differential Revision: D22684908

fbshipit-source-id: bb00bf2896880ae6ed5f189110bb13b5abbd80cd

Summary:
detachOnCancel adapter can be used with Awaitables that don't support active cancellation, but are safely detachable. When the cancellation is requested the adaptor will emit OperationCancelled exception without waiting for the awaitable to complete.

This diff also introduces tryAssign helper, similar to Try::operator=, but which handles a case of throwing move constructor.

Reviewed By: lewissbaker

Differential Revision: D22578847

fbshipit-source-id: cab9998c8c6a709108edefc3d59e6f44792d562f

Summary:
[Folly] Add a missing `std::forward` in `makeAsyncTask`.

As a matter of policy in folly futures, continuations are invoked with the cv-ref qualifiers (excluding v qualifiers) with which they are passed. Here is a case where the policy was not upheld.

Reviewed By: ericniebler

Differential Revision: D22672148

fbshipit-source-id: b8dba221914221d390617fa1c69736c5c547e40c

Summary:
The shallow copied child RC is often used to make small changes to the RC for a limited scope of the request.

The tracepoint however reports the raw address of the RC as a way to identify the request itself - Therefore we end up reporting different identifiers for what is 'logically' the same request.

This diff adds two additional arguments (the rootIds or pointers to the parent RC) to allow bpf programs to pick up this subtlety.

Reviewed By: yfeldblum

Differential Revision: D22424318

fbshipit-source-id: f669cabca10fa50b8a81fb4b3585d30654207e4c

Summary:
This diff adds heterogeneous lookup support and eraseInto to the
fallback (non-SIMD) version of F14 sets, which is used on mobile.
std::is_invocable<hasher, const_iterator const&> is no longer evaluated
during erase.  It also restructures F14MapTest and F14SetTest so that
as many of the tests as possible run in the fallback mode.

(Note: this ignores all push blocking failures!)

Reviewed By: yfeldblum, ot

Differential Revision: D21489440

fbshipit-source-id: 872a250f8a6ec3c9efcd19edb7d9beca196fa865

Summary:
This diff implements efficient heterogeneous lookup, insert,
and erase for the fallback (non-SIMD) mode of F14.  It relies on internal
implementation details of the underlying std::unordered_map implementation
that happen to be true for libstdc++, libc++, and MSVC.

Extending this technique to F14 sets would be straightforward, but has
not been done here.

(Note: this ignores all push blocking failures!)

Differential Revision: D21408628

fbshipit-source-id: 72e9ddd82a50c02ec762d4b64dc3303848bd0218

Summary:
getTry reads like a blocking operation but is actually non-blocking.

Remove to avoid confusion.

(Note: this ignores all push blocking failures!)

Reviewed By: yfeldblum

Differential Revision: D22494732

fbshipit-source-id: d884d60cc14e2a53cd0657926a885a12b994c1ee

Summary:
This is a pretty cryptic race condition, but it works like this:

Each thread local instance (i.e. one ThreadLocalPtr) is assigned a unique ID by the static meta. This ID is freed up when the thread local is destroyed, and may then be reused by another newly created thread local.

For each thread we keep an array of elements (ElementWrapper), indexed by the thread local ID. Each element has some metadata such as the pointer to the object being cached for that thread and that thread local.

There are a few cases where we access a ElementWrapper object:
 - We write to it under a global lock, when destroying a thread local object (only the i-th element is written to for each thread, if the ID is 'i' for the thread local).
 - We write to it under a global lock, when reallocating the array of elements for the thread if a new thread local ID exceeds the capacity of the array; this can happen when we are reading the thread local for a thread.
 - We write to it under a global lock when the corresponding thread is destroyed.
 - We read from it, *without* any locks, when reading a thread local's value from a thread and the above reallocation case does not occur.

The race condition happens in this case:
 - Thread locals A and B are created
 - Thread local A is accessed by thread Z, and gets, say ID = 5, the corresponding element E is initialized
 - Thread local A is destroyed by thread X, and under the global lock, the element E is written to (setting element->ptr = nullptr); ID 5 is released to the list of free IDs.
 - Thread local B is accessed for the first time by thread Y, and therefore needs to grab an ID; under the global lock, it happens to get ID = 5, and stores that ID into the thread local instance as an atomic int; the store here uses std::memory_order_seq_cst.
 - Thread local B is then accessed again from thread Z; this time the atomic int ID is loaded with std::memory_order_relaxed, with the resulting value of 5; we then proceed to read element E's ptr value *without any locks*.

TSAN reports the last read of element E to be racy with the previous write of element E during thread X's destruction of thread local A. Even though this happened with a mutex operation in between, the final std::memory_order_relaxed causes TSAN to think that the read access was not properly synchronized after the earlier write.

This conjecture is confirmed by the following small reproducible test case:

```
TEST(MyTest, Test) {
  std::mutex mutex;
  int x = 0;
  bool written = false;
  std::atomic<bool> seen{false};

  std::thread t0([&] {
    while (!seen.load(std::memory_order_relaxed)) {
    }
    std::cout << x;
  });

  std::thread t1([&] {
    while (true) {
      std::lock_guard<std::mutex> guard(mutex);
      if (written) {
        seen.store(true, std::memory_order_release);
        break;
      }
    }
  });

  std::thread t2([&] {
    std::lock_guard<std::mutex> guard(mutex);
    x = 1;
    written = true;
  });

  t0.join();
  t1.join();
  t2.join();
}
```

(This example, when run under TSAN, reports a race condition between "x = 1" and "std::cout << x".)

This change makes the load use std::memory_order_acquire so it synchronizes with the store. Should have no performance implications on x86 but I'm not totally confident about that.

While we're at it, also changing the allocate() and destroy() functions to use more relaxed memory orders; sequential consistency is unnecessary in these places.

Reviewed By: yfeldblum

Differential Revision: D22561685

fbshipit-source-id: 0d53925486ef78139ffe71681827b0c0959dd29e

Summary:
libstdc++ versions that don't include N4387 ("perfect initialization" for
pairs and tuples) can't use the two-arg pair constructor as an emplace
target when the emplace args don't exactly match the destination types.
(libstdc++.so.6.0.22 is the first one that contains the improvement,
which corresponds to gcc 6.1.0).  This diff guards the optimization added
in D21419822 (https://github.com/facebook/folly/commit/7d618e4fde39b44e0952880653e10ec97400583f) with an enable_if test to avoid the problem, and includes
the template parameter changes necessary to get the target types to the
test site.

(Note: this ignores all push blocking failures!)

Differential Revision: D21766560

fbshipit-source-id: f8b2a0230504237f976e14b0740bb31bc7a57b77

Summary:
[Folly] A test for the `atomic_ref` deduction guide, which permits removal of the preprocessor guard in the definition of `make_atomic_ref`.

Some parts of folly still support legacy versions of C++ but we do not necessarily run the tests on legacy platforms.

Reviewed By: akrieger

Differential Revision: D22635366

fbshipit-source-id: 8961d3465b63875a660d9e83d094ebf0cd64d1df

Summary: Add a `clear()` API to render the Arena like new, except that previously-allocated blocks are preserved to be reused in the future.  (Caveat: we do not reuse "large blocks")

Reviewed By: yfeldblum, davidtgoldblatt

Differential Revision: D22209898

fbshipit-source-id: c2f27d70ee09855df8c8c6fc6d162fca92b9eac8

Summary:
[Folly] Mark invoker `operator()` as `[[maybe_unused]]` when defined in macros.

If the macro is used in a `.cpp` but the generated `operator()` is not invoked, the compiler might warn.

This can easily happen in the following situation:

```
FOLLY_CREATE_MEMBER_INVOKER(invoke_foo_fn, foo);
FOLLY_CREATE_MEMBER_INVOKER(invoke_bar_fn, bar);

using invoke_one_fn = std::conditional_t<
    /* cond */,
    invoke_foo_fn,
    invoke_bar_fn>;
constexpr invoke_one_fn invoke_on;

template <typename T>
void go(T& t) {
  invoke_one(t);
}
```

In such a situation, either `invoke_foo_fn::operator()` is seen at a call-site or `invoke_bar_fn::operator()` is seen at the call-site, but not both - one of them is unused, and if the right warnings are enabled, will be warned as unused.

Reviewed By: luciang, markisaa

Differential Revision: D22570047

fbshipit-source-id: a4caa7a95ab74ea075cf41c26525935f3d9186c0

Reviewed By: yfeldblum

Differential Revision: D22604684

fbshipit-source-id: 4dedb9c831d0a2137d16bbe0514e00a1c8f77f4a

fbshipit-source-id: 798decc90db4f13770e97cdce3c0df7d5421b2a3

fbshipit-source-id: 5113fe0c527595e4227ff827253b7414abbdf7ac

Summary: [Folly] `FOLLY_KEEP` for keeping function definitions when using function-sections even if the linker would remove them.

Reviewed By: alexshap

Differential Revision: D22575832

fbshipit-source-id: 08410b3c318e361b1f3efcbb8f168091faed86e8

Summary: For program running in different general user contexts, e.g. services, multithreading, it's very useful to extend log prefixes to contain the domain specific context strings in debugging. This diff adds one interface function to push one callback to the logger. The callbacks will be executed when the log message data is constructed, and the strings returned by callbacks will be appended to the tail of log entry prefixes.

Reviewed By: simpkins

Differential Revision: D21291284

fbshipit-source-id: e141bf1c907f6730ea741d0dc06975add93d489c

Summary:
`folly::coro::Materialize` uses a `union` of `ManualLifetime` objects to store either the result (value) or the error of an async operation. However, it accesses these fields without ever activating them by in-place constructing the `ManualLifetime` objects. Likewise, when changing the active field, the `ManualLifetime` objects must by destroyed. It doesn't matter that these operations are no-ops. The must be there to avoid UB, which can manifest at higher optimization levels.

I fix this by providing two functions: `activate` and `deactivate`, for use constructing and destructing values in `ManualLifetime` objects when those objects are fields in a `union`.

Reviewed By: yfeldblum, kirkshoop

Differential Revision: D22527895

fbshipit-source-id: 8cc1c3fae75672387d977dddeff61c82093abb9a

Summary:
This diff adds a minimal workflow for running integrations tests for Mononoke. Currently only one test is run and it fails.

This also splits the regular Mononoke CI into separate files for Linux and Mac to match the current style in Eden repo.
There are the "scopeguard::defer" fixes here that somehow escaped the CI tests.
Some tweaks have been made to "integration_runner_real.py" to make it runnable outside FB context.
Lastly the change from using "[[ -v ... ]" to "[[ -n "${...:-}" ]]; in "library.sh" was made because the former is not supported by the default Bash version preinstalled on modern MacOS.

Pull Request resolved: https://github.com/facebookexperimental/eden/pull/26

Reviewed By: krallin

Differential Revision: D22541344

Pulled By: lukaspiatkowski

fbshipit-source-id: 5023d147823166a8754be852c29b1e7b0e6d9f5f

Summary: remove pushmi from folly

Reviewed By: yfeldblum

Differential Revision: D22531090

fbshipit-source-id: 3e6561f220cc3fd227dec321112ec848c4f17c6f

Summary:
Add warning about using the default inline executor for asynchronous reclamation, which may lead to deadlock if there are unintended circular dependencies. The use of inline executor is likely due to not calling folly::enable_hazptr_thread_pool_executor at some earlier point (e.g., due to not calling folly::init()).

Also changed some function names for easy identification and fixed typos.

Reviewed By: yfeldblum

Differential Revision: D22536210

fbshipit-source-id: 89e74411a909ec97b03e8ff90f7039ab233c087b

Summary:
Pull Request resolved: https://github.com/facebookexperimental/eden/pull/27

Pull Request resolved: https://github.com/facebookexperimental/rust-shed/pull/9

Original diffs: D22417488 (https://github.com/facebook/folly/commit/43d80f110b181dd7f72f0f935322a58f9cbb5147), D22528869 (https://github.com/facebook/folly/commit/3930a6ef4437f161c50ac27141cd397eda999fa7)

Reviewed By: markbt

Differential Revision: D22571972

fbshipit-source-id: c6f013565680a757b642dd79e647207fce3351ec

Summary: Fix building folly sysuio portability when targeting the iOS simulator, because the current Xcode 12 SDK does not contain `preadv` and `pwritev` for the iOS simulator on Catalina, even though it declares it's there, so we get link errors.

Reviewed By: yfeldblum

Differential Revision: D22569172

fbshipit-source-id: 870b47063cb37a24364d1de292aba1f966edfb7c

Summary:
This diff adds a constructor that takes an `AsyncSocket*`, so that lifecycle observers are informed via `move` when a socket is transformed.

If one `AsyncSocket` is constructed from another using the `AsyncSocket(AsyncSocket* oldAsyncSocket)` constructor, then `move(oldSocket, newSocket)` will be triggered for attached observers, allowing the observers to detach from the old socket and attach to the new socket. However, we currently transform between `AsyncSocket` by detaching the fd and event base, and passing them to the new constructor:

```
# from FizzAcceptorHandshakeHelper.cpp
auto evb = transport_->getEventBase();
auto fd = transport_->getUnderlyingTransport<folly::AsyncSocket>()
                ->detachNetworkSocket()
                .toFd();
transport_.reset();
sslSocket_ = createSSLSocket(sslContext_, evb, fd);
```

When this happens, any `AsyncSocket::LifecycleObserver` that were attached on accept to become separated from the fd/socket that they're attempting to follow. With this change, we can do the following instead (next diff):

```
 sslSocket_ = createSSLSocket(
      sslContext_, transport_->getUnderlyingTransport<folly::AsyncSocket>());
transport_.reset();
```

Because `createSSLSocket` uses the `AsyncSocket*` constructor, the `move` observer event will be triggered.

Differential Revision: D21614835

fbshipit-source-id: 6c995f879fe41935850247a28ff8af2b33349445

Summary:
Adds `AsyncTransport::LifecycleCallback`, an observer that is notified when a transport is closed and destroyed.

Currently only supported for `AsyncSocket` and derived types (e.g., `AsyncSSLSocket`).

`AsyncSocket::LifecycleCallback` is derived from `AsyncTransport::LifecycleCallback` and adds support for additional lifecycle events relevant to `AsyncSocket`.

Details:
- Can be used by instrumentation that ties its lifetime to that of the transport.
- Intentionally separate from all existing callbacks that may be added / used by application logic because it is designed to be used by instrumentation that is generic, and thus separate / unaware of application logic.
- Multiple observer can be registered, but a `folly::small_vector` is used to minimize alloc overhead in the common case of 0 - 2 being registered.
- The observer implementation is responsible for calling `removeLifecycleObserver` to remove itself if it is destroyed before the socket is destroyed.

Differential Revision: D21613750

fbshipit-source-id: 92bb5de30bc8bab56fa29e62800bf58e47486f1e

Summary:
We have traditionally used `WriteFlags::EOR` to communicate that ACK timestamping should occur. This is confusing and mostly for legacy reasons when we had a custom kernel patch that would send ACK timestamps if the EoR flag was set.

Creating proper flags for ACK and SCHED timestamps. I will integrate the logic that uses these flags into `AsyncSocket` in a subsequent diff.

Differential Revision: D22039799

fbshipit-source-id: 23f534365475bb67f91d86657919cce02439f0c8