Summary:
Thread 1:
  - Creates an eventfd X
  - Registers X with an event base
  - Closes X
  - Unregisters X from the event base

Thread 2:
  - Creates some other file descriptor (eventfd or socket or whatever); the operating system reuses file descriptor #X.

The unregistering of X from the event base in thread 1 races with the opening of reused X in thread 2.

The fix is to unregister X before closing X.

Reviewed By: yfeldblum

Differential Revision: D27962155

fbshipit-source-id: 1bcb62c7ebe0297ab9687e1a0edf37d319637fda

Summary: Replace the uses of `FOLLY_CL_USE_FOLLY_TLS` in some cases with C++ checks on `kIsMobile`.

Differential Revision: D27669672

fbshipit-source-id: 79a29896653f2fa62b10b488220d8cf83cba3d00

Summary: To use `std::atomic`, we need `#include <atomic>`.

Reviewed By: Mizuchi

Differential Revision: D27932606

fbshipit-source-id: 8d29a56a75b27ae35bac37b87a7e6d6d1661030e

Summary: The facility was renamed in gtest.

Reviewed By: praihan

Differential Revision: D27904281

fbshipit-source-id: 3f00b4371e17cd85672ad7ef706cea4ca1ba5c64

Summary: On apple platforms, posix sem is deprecated. On windows, it does not exist. So switch to the native-semaphore wrapper.

Reviewed By: chadaustin

Differential Revision: D27903002

fbshipit-source-id: d53c7762fea3123cf67cda48fdd87489a0ee496c

Summary:
A semaphore type which wraps the platform native semaphore type.

On Windows, this is the Windows semaphore type. On Apple, this is the semaphore type from libdispatch. Otherwise, this is the POSIX semaphore type, which is deprecated on Apple and unavailable on Windows.

Reviewed By: Orvid

Differential Revision: D27951114

fbshipit-source-id: e6a870f656eecd3ba41c2efed038b916c124d0e8

Summary:
The migration to tpx broke Watchman's tests because test_bser relies on YARN_YARN_OFFLINE_MIRROR being set in the environment and tpx doesn't forward environment variables into the test.

Explicitly forward them ourselves.

Reviewed By: fanzeyi

Differential Revision: D27897172

fbshipit-source-id: 16c8017a89979802bd9d443825ed4e22cb6ff6c9

Summary:
This diff enables a symmetrical pattern to `makeGuard()`/`dismiss()`: `makeDismissedGuard()` will create a guard that will not execute unless `rehired()`'d.

This is for use cases where the guard's scope is wider than where the condition on whether it should execute is evaluated. For example
```
State state;
auto guard = makeDismissedGuard([&] { cleanup(state); });
if (modifyStateInAWayThatRequiresCleanup(state)) {
  guard.rehire();
}
// Use state.
```

Reviewed By: yfeldblum

Differential Revision: D27931274

fbshipit-source-id: fbf7048dc991b73553cd6429f5e73345e4104d49

Summary:
Permit calls of the form:

```lang=c++
FOLLY_SAFE_DCHECK(expr);
```

Reviewed By: ot

Differential Revision: D27843903

fbshipit-source-id: 23869720822fcdba0845c42279855b101c8e2b36

Reviewed By: praihan

Differential Revision: D27800735

fbshipit-source-id: 26f2c1be72bb66864173beb87244129dd6194c8d

Summary: It is possible to have concurrent calls to `SingletonVault::setType` and `SingletonHolder::createInstance`. In which cases, non-atomic accesses to `SingletonVault::type_` race.

Differential Revision: D27904167

fbshipit-source-id: be01ee375d37839629b2e1d64bec99e32cd7e213

Summary:
Add a benchmark for `rcu_retire`. Remove perf code from the rcu tests.

As a motivating side-effect, removes faulty calls to `printf` which fail to compile across platforms, including mac.

Differential Revision: D27902852

fbshipit-source-id: 1698a0fd8ca3731f0b794cb1c2cb08c4bfb5d714

Summary:
Using `extern template struct` can be tricky - best to avoid.

Use static storage but no longer use static initialization to avoid all issues surrounding ODR, global initializers, etc. Microbenchmarks show no significant hit.

Add a global constructor to continue triggering initialization at static initialization time.

Differential Revision: D27746718

fbshipit-source-id: c5288c33412a80bb813c8d615794b9773cef323c

Differential Revision: D27859994

fbshipit-source-id: afde93e853a08a3d65f3d817cd2bbad337bfbfce

Summary:
To encourage migration to safer executors, add transitional *Unsafe names for the old, mutable, global executors. This is consistent with the use of *Unsafe elsewhere in the async framework.

(Note: this ignores all push blocking failures!)

Reviewed By: yfeldblum

Differential Revision: D26418111

fbshipit-source-id: 414ee238ed4ae43619ce8d671fa5725f0679f67e

Summary:
It looks like the various CMAKE_CXX_FLAGS_* are simply ineffective, and I'm not
sure why, setting CMAKE_CXX_FLAGS does work though, and CMake appears to add
some release/debug flags to it when generating Ninja files.

Reviewed By: fanzeyi

Differential Revision: D27862117

fbshipit-source-id: a89f6182b5bae9a087f8fcfd4c5f9526f91e2adf

Summary: Avoid calling arbitrary user code from within the scope of framework `catch` blocks. Instead, get the current exception in the catch block, save it, and call the user code after.

Differential Revision: D27842318

fbshipit-source-id: de3ebabc5c08332701a619a93b6e01bfccc0ea71

Summary:
Storing the `__PRETTY_FUNCTION__` for logging has an unreasonable cost on (non-strippable) binary size for debug builds, as different template instantiation will produce long, demangled, and non-mergeable strings.

If necessary, all the information is retrievable from the debug info (even if the function is inlined), where it's stored in much more efficient form. So, switch to `__func__`, which is stripped.

Reviewed By: yfeldblum, luciang

Differential Revision: D27825136

fbshipit-source-id: d499084c7e7b24db1cd46aa2b03f4a590c6eddc3

Summary: Doing so is a bug that can take some time to pin down. Fail at the callsite instead to make this easier.

Reviewed By: yfeldblum

Differential Revision: D27829947

fbshipit-source-id: e3628331ffb687718309e130e8e0f2f78c4eb1aa

Summary:
Add support for AsyncSocket connect bind to device

(Note: this ignores all push blocking failures!)

Reviewed By: danobi

Differential Revision: D27784176

fbshipit-source-id: d7efe3ef59b26aa69552d5f8109f89457ee5fe66

Summary: To avoid the marginal but still unnecessary compile-time cost of constructing a lambda. And enclose the full thing in braces so it can be used in an unbraced `if`.

Reviewed By: ot, luciang

Differential Revision: D27817005

fbshipit-source-id: 9a1a6e0389fea5907a3a20cffbd6a029b0a85eb9

Reviewed By: Mizuchi

Differential Revision: D27669414

fbshipit-source-id: 617e0b5f17fa8ce5505f7f16b00516ba7f21b064

Summary: Why is unsafeGetUnlocked() used here? It seems obviously not safe when we're iterating on the vector after. Am I missing something?

Reviewed By: andriigrynenko

Differential Revision: D27748519

fbshipit-source-id: fe8a78408fdf59e83f5261740e4703f876ad9f9d

Summary: Avoid enlarging data sections. The use of `static` causes data sections to be smaller in certain critical cases.

Reviewed By: cmds, luciang

Differential Revision: D27813138

fbshipit-source-id: 020b14927be5ac035d5f66e7cd652a58f8f820d0

Summary:
Add support for AsyncSocket readv operations

(Note: this ignores all push blocking failures!)

Reviewed By: danobi

Differential Revision: D27585275

fbshipit-source-id: d9a410a4c5d60af06c187e0abb5bd11b7054a6b9

Summary: Should address various build issues.

Reviewed By: Orvid

Differential Revision: D27699043

fbshipit-source-id: 7bcb827c3372e6243554e8bf04426c041b2c62a4

Summary:
It's not safe to expect that the executor is alive after a task is added to the queue (this task could be holding the last KeepAlive and when finished - it may unblock the executor shutdown).
The fix is to hold a KeepAlive if some operation has to be done after adding to the queue. However it's safe to avoid this in a case where executor thread count will never drop below 1 (otherwise not having active threads may result in a deadlock) and we already have the maximum number of threads running. This optimization should help avoid grabbing the KeepAlive on the fast path.

The difference from the previous implementation is that we still start with 0 threads. But keep minThreads at at least 1.

Differential Revision: D27751098

fbshipit-source-id: 7b992a73b40984376893c1fe2a4a072002f0a12a

Summary: To differentiate serialization and deserialization errors.

Reviewed By: yfeldblum

Differential Revision: D27743086

fbshipit-source-id: 8eb4fe1a1733e3effd0aa0478f59160381738db2

Summary:
The build was failing at link time with the claim that `__PRETTY_FUNCTION__` was in a discarded section. This occurs only under some versions of gcc with asan enabled.

This approach works by making a copy of `__PRETTY_FUNCTION__` without ever taking a reference to it.

This may not be the ideal fix, but it is the first one that worked upon experimentation.

Differential Revision: D27786615

fbshipit-source-id: 2845c85bdc8158d4b2da7cd200ce55f982285a21

Summary: Since `[[gnu::weakref]]` can be used effectively in cases where `[[gnu::weak]]` cannot.

Reviewed By: Orvid

Differential Revision: D27672340

fbshipit-source-id: 4882f0176726aece411359c25411f0f4be7fc59f

Summary: Add some functions for looking at the code generated by `AccessSpreader<>::current()` and `AccessSpreader<>::cachedCurrent()`.

Differential Revision: D27747508

fbshipit-source-id: 0bc44938e810ec76ead50b6d4c1ade4aec9f8282

Summary:
Add support for AsyncServerSocket bind to device

(Note: this ignores all push blocking failures!)

Reviewed By: danobi

Differential Revision: D27778929

fbshipit-source-id: fa051be2aa5c1b3df5e0c0f30adc3a58de7b7704

Summary: Since HeaderClientChannel now accepts a transport unique_ptr there's no need to have this deleter exposed outside of HeaderClientChannel.

Reviewed By: iahs

Differential Revision: D27729209

fbshipit-source-id: 064b03afdfe567b6df6437348596f0f6f97f6aaf

Summary:
Pull Request resolved: https://github.com/facebook/folly/pull/1561

As title.

Reviewed By: jdq

Differential Revision: D27736665

fbshipit-source-id: 2f09ea4dad25389a46faccca4a5803ea9e077e0d

Summary:
Create a new class, ConstructorCallback, that when included as a member in
another class (e.g., Foo) allows other functions to register and receive
callbacks every time any of Foo's constructors are called.

Main implementation concern is to be extremely lightweight (e.g., avoid locks)
assuming that most code calling this will be performance optimized (both
for CPU and mem).

Implement as a static array of functions:

1) Static array instead of dynamic (e.g., vector):
  vector occasionally resizes so avoid locking during resize
2) Don't allow removing callback functions:
  simplify the calling of funcitons, again to avoid locks and races
3) Use function callbacks instead of objects with an observer pattern
  (e.g., like AsyncSocket::LifecycleObserver) to ensure that there
  won't be races on shutdown.  Functions are static where classes can
  de-allocate at shutdown and since we don't allow un-registering the
  call back, it's not easy to remove the race for a class.

Reviewed By: simpkins

Differential Revision: D27056139

fbshipit-source-id: 0846e0d55124cfde2e15acbe18e01ca5e327e7df

Summary:
`DigestBuilder` caches the cpu id and invalidates it when it detects contention, but the critical section is small enough that it is possible for two thread to end up on a conflicting slot but not detect it for some time, causing cache-line pingponging in the meantime.

Switch to `cachedCurrent()` instead, which uses the number of accesses to invalidate the cache, and is successfully adopted by other high-concurrency primitives.

Reviewed By: yfeldblum

Differential Revision: D27726518

fbshipit-source-id: 05d70ad9f101df4a8797e44cc3cbe94cbd1cb7b8

Summary:
GmockHelpersTest.cpp is the only one that fails to build with GCC after this change.
Also only 5 tests are failing at this point.

Reviewed By: pixelb

Differential Revision: D27728248

fbshipit-source-id: ded994f466347a8826ba90429a13237c21d3af5e

Summary:
F14 map `iterator` doesn't define `operator==` or `operator!=` to itself.
Those member functions take `const_iterator` as the right-hand side,
relying on the ability to convert implicitly from `iterator` to
`const_iterator`. This interacts poorly with c++20's default equality
operators, triggering clang's `-Wambiguous-reversed-operator`.

This diff replaces the equality member functions with friends that use
the same left-hand and right-hand types.  iterator != const_iterator
will now compile by implicitly converting the left-hand-side and then
calling `operator!=(const_iterator const&, const_iterator const&)`,
rather than calling `iterator::operator!=(const_iterator const&)`.
This resolves the ambiguity in c++20, and should work fine on earlier
versions, although I have not tested it on anything except c++17.

Pull Request resolved: https://github.com/facebook/folly/pull/1544

Test Plan: does it build?

Reviewed By: yfeldblum

Differential Revision: D27479086

Pulled By: shixiao

fbshipit-source-id: 0d42dbdc056cec58a36de3a816883736a761d0f6

Summary: Consistently use `Observer` and `Snapshot` like everywhere else in these files instead of `folly::Observer::{Observer,Snapshot}`.

Reviewed By: yfeldblum

Differential Revision: D27685699

fbshipit-source-id: 7eca35b9d113d8d9cd8ca631be2ad54c827431ea

Summary:
Nothing uses the skipFraction in LockFreeRingBuffer::currentTail, and
floating point math for discrete fractions can be hard to reason
about, so remove this dead code.

Differential Revision: D27717906

fbshipit-source-id: b25e2bea25ab66c59e8c76a80d75140db474c46d