Summary:
prepare() blocks mostly just lock locks, but we don't know what order to lock - so similar
to std::lock, just iterate using try_lock until success.

Reviewed By: ot

Differential Revision: D7676738

fbshipit-source-id: 2e0d28e4829a3a21d361a5801383c1aad0d66757

Summary:
Summary of the changes
 ---
- Fix broken MSVC build:
  - Compiling `GenerateFingerprintTables.cpp` complained about missing header file `glog/logging.h`.
  - Targets `GenerateFingerprintTables` and `folly_fingerprint` don't specify `FOLLY_INCLUDE_DIRECTORIES` in its include directories.

* Introduce a "shiny" target `folly_deps` for managing folly's dependencies and interface specification.
  * `folly_deps` is an [INTERFACE library target](https://cmake.org/cmake/help/v3.0/command/add_library.html).
  * It encapsulates the interface dependencies (compile definitions, include directories, link libraries, etc.) for other targets.
  * The usage of the new target is clean and simple:
    `target_link_libraries(<target_name> (PUBLIC|PRIVATE) folly_deps)`
    (except for OBJECT library targets, like `folly_base` - included in the change).

Possible modifications
 ---
The name `folly_deps` could be replaced with a better one.
The target can be extended to include the PUBLIC compile options set on individual targets.
Reviews and suggestions welcome.
Closes https://github.com/facebook/folly/pull/818

Reviewed By: simpkins

Differential Revision: D7642870

Pulled By: Orvid

fbshipit-source-id: c1c5fdae67f5a677c82f05757217af6b6de9db02

Summary:
Turns out we needed this method to be virtual to mock it out in tests because it makes
a bunch of syscalls.

Reviewed By: yangchi

Differential Revision: D7665938

fbshipit-source-id: 1ae5768ade2c927929f5cb1f9e1ad62dad1ba237

Reviewed By: aary

Differential Revision: D7680645

fbshipit-source-id: 6a3742c215a6924ec5c1c5b8bc1d2bff315355e7

Summary:
Add `try_lock` methods to `folly::Synchronized` and add the corresponding
extensions to `LockTraits`.  These return `LockedPtr`s that are valid and
convert to true when the lock operation was successful, null otherwise

override-unit-failure

Reviewed By: yfeldblum, ot

Differential Revision: D7651765

fbshipit-source-id: eb85987a2e4476cd916747dfc2ae69d124690ee6

Summary: TDigest is designed to process a stream of data in batches. DigestBuilder is a fast, thread safe approach for buffering those writes and building a digest.

Reviewed By: davidtgoldblatt

Differential Revision: D7582745

fbshipit-source-id: 528ad9b21685746887b3a602d433662221fb875a

Summary:
Use new refcount hazptr feature.

This prevents many roundtrips through release()->retire()->~Node()->release()->retire() etc, and instead can call delete immediately through most of the chain

See D6142066

Reviewed By: yfeldblum

Differential Revision: D6290004

fbshipit-source-id: d8cfb2aa41260918a7f201765febc31d558742bb

Summary: Revert "Use unbounded queue in NotificationQueue"

Reviewed By: magedm

Differential Revision: D7669679

fbshipit-source-id: 269139fc8238896640fc60ed36c83e728ed489b4

Summary: This diff adds reads for sum, mean, and count on TDigest. The results are calculated at merge time, to make reads O(1).

Reviewed By: anakryiko

Differential Revision: D7639133

fbshipit-source-id: bb8f203ec0ed3197f090d2ce9223a2e9d1bca752

Summary:
Unset the error message callbacks when err
message so that we dont deliver errors when
not needed

Reviewed By: yfeldblum

Differential Revision: D7661052

fbshipit-source-id: 5a2330b2cd11f844649d56343307e2c75b626bdc

Summary: blame D7477268.  Some callsites use UnboundedBlockingQueue with non-copyable CPUTasks, must also have std::move here.

Reviewed By: yfeldblum

Differential Revision: D7655710

fbshipit-source-id: cf8dba1df0c1703ffea1c0c0445c7d14deaf1d61

Summary: Add missing markdown notation

Reviewed By: shixiao

Differential Revision: D7655769

fbshipit-source-id: a0db34846e48afd845b8878de84764d30330b096

Summary:
add try_take_for to BlockingQueue, utilizing new LifoSem::try_wait_for method.
To be used to kill threads after an idle period in CPUThreadPoolExecutor.

Reviewed By: magedm

Differential Revision: D7477268

fbshipit-source-id: 76ea7fa1fc3b4b5f7a7529ce1424a91eef2ac7b1

Summary:
Linux's futex checks the waiter count atomically before grabbing the lock.  This results in much better perf if there are no waiters and you call futexWake().
Add the same improvement to ParkingLot.

Reviewed By: yfeldblum

Differential Revision: D6639337

fbshipit-source-id: 6e03eff07e4c9ce327bc66d0aabd8cec051a5b19

Summary:
According to headers, `pthread_getname_np` and `pthread_setname_np` are available since iOS 3.2 and macOS 10.6.
However, guarding just on min macOS version isn't going to work for iOS/watchOS/tvOS, because it's very rarely defined.
So add another case for when `__IPHONE_OS_VERSION_MIN_REQUIRED` is defined and is above iOS 3.2, which will also make watchOS and tvOS work.

Reviewed By: yfeldblum

Differential Revision: D7648204

fbshipit-source-id: 1e608cdad3f39242eff79fbb6da8e560eeee720a

Summary:
If the default inline executor is used for folly::window, and all the futures generated by the callback are also inline, then all spawn function calls (and their associated Futures) are added to the call stack and can overflow. This fixes that issue by using QueuedImmediateExecutor, which will put the executor callback into a thread-local queue, allowing the current function to exit and destruct all objects in its stack frame. Then, only the first call to QueuedImmediateExecutor in a thread is responsible for running each subsequent callback and will do so sequentially.

This will end up allocating dynamic queues that reach a max size of two. It is possible to avoid a dynamic queue by writing a new Executor that only stores a single function, if that is too much of a performance cost.

Reviewed By: yfeldblum

Differential Revision: D7597731

fbshipit-source-id: cd8899e6c086ecff812050f7241e80f39c546706

Summary: Avoid creating a loop in the ThreadEntryList in onThreadExit

Reviewed By: djwatson

Differential Revision: D7632840

fbshipit-source-id: 409358aae16a8aed4ae654ebfeca994385b43a9e

Summary:
Neither GCC or Clang are able to optimize a `memcpy` where
the length is known to be smaller than a word: a library call is
generated. This is a simple implementation of a subword
`loadUnaligned` to be used to read the tail of a buffer when reading
one word at a time.

Reviewed By: luciang

Differential Revision: D7631978

fbshipit-source-id: d5719580e6bef82aa8e3fbdce8f873b569527a3a

Summary: This function is no longer used anywhere.

Reviewed By: Orvid

Differential Revision: D7597741

fbshipit-source-id: 296acfceb59293bbafc6f6bf9c67d951cf41f7be

Summary:
Update `make_temp_dir()` to use `shutil.rmtree()` to clean up rather than just
`os.rmdir()`.  If the function using this context manager throws it may leave
behind files inside the temporary directory, and it is useful to always clean
those up.

Also update `read_fbcode_builder_config()` to work regardless of the current
working directory.  Previously this function only worked if the current working
directory was the directory containing the configuration file.  This makes sure
that `read_fbcode_builder_config()` calls are always treated as relative to the
directory containing the configuration file being read.

Reviewed By: yfeldblum

Differential Revision: D7597743

fbshipit-source-id: 817063104081336fcc0a9f825beb74d7d4377499

Summary: Creates a new SlidingWindow data structure for general purpose use in stats code.

Reviewed By: anakryiko

Differential Revision: D7597047

fbshipit-source-id: 227438055029c2bacb5edf2943ebc9cc66fdfe36

Summary: Use unbounded queue in NotificationQueue (prev changes: D7164130, D7251343, D7278275, D7359322, D7471153, D7606076)

Reviewed By: djwatson

Differential Revision: D7408628

fbshipit-source-id: 04ae235d9b3de603e28115e11fe98fe7e9aa1f8c

Summary:
fixes #819.
Closes https://github.com/facebook/folly/pull/820

Reviewed By: yfeldblum

Differential Revision: D7642932

Pulled By: Orvid

fbshipit-source-id: c49168ddf111c851d0218b74fbbdf405e9a68fc3

Summary:
- Expose an API to erase an item from `F14Set` and do something with it before it is destroyed
- This includes (but is not limited to) being able to `std::move` it to another container while avoiding a copy
- Change erase implementations to forward to `eraseInto(...args, emptyCallback)`

Reviewed By: shixiao

Differential Revision: D7588928

fbshipit-source-id: 5e9c2bda216c5c219c333282daadd2170e6a1eba

Summary:
Adds the ability for UDP sockets to optionally
listen to errors that happen on the socket,
for example ICMP errors.

In this iteration, we explicitly do not register for
read events if an error callback is set. So even
if you set an error callback to get error events
you must register a read callback.

Reviewed By: yfeldblum

Differential Revision: D7632877

fbshipit-source-id: 43c922d0145e1da97b993f5bf4058c20d3469deb

Summary:
Clang format files related to AsyncUDPSocket.
This helps keep changes consistent.

Reviewed By: yfeldblum, lnicco

Differential Revision: D7632865

fbshipit-source-id: 0761f0cfd06417334e680ca0880280d65480fe7e

Summary: [Folly] Tweak `SharedPromise` and `FutureSplitter` docs, in particular to reflection recent changes to execution semantics.

Reviewed By: LeeHowes

Differential Revision: D7630725

fbshipit-source-id: 68da70cd86d131aa09c1909d90a793868039e84f

Summary: [Folly] All comparison predicates for `IOBuf`, not just `EqualTo`.

Reviewed By: djwatson, stevegury

Differential Revision: D7596700

fbshipit-source-id: 2d5cef2797dc75d4fb76c2d13e4a938f738da163

Summary: [Folly] comparison-to-predicate adapters for comparisons which return `ordering`.

Reviewed By: stevegury

Differential Revision: D7596712

fbshipit-source-id: 1aeccf0d38eec27cfa88af2908f3114523d6b6b5

Summary: [Folly] `to_ordering` to convert from `int` to `ordering`.

Reviewed By: stevegury

Differential Revision: D7596709

fbshipit-source-id: cf1316a7560b9398b94d1c834258f09a797a98f8

Summary: [Folly] An `ordering` type, lifted from `FixedString`.

Reviewed By: stevegury

Differential Revision: D7596713

fbshipit-source-id: ba19e1e36e75b946e14f6db9c72ac1ac3c7270e9

Summary:
D7479058 changed the exception_tracer code to export their targets in the main
folly-targets.cmake file, but I forgot to remove the `install()` command
installing the old `folly-exception-tracer-targets.cmake` file.

This would cause `cmake configure` to exit with an error if it detected it
could built the exception_tracer code, but it would still generate all of the
necessary Makefiles correctly, so subsequent `make` commands would still work.

Reviewed By: yfeldblum

Differential Revision: D7626710

fbshipit-source-id: f015032c3c42cf2911fcaf9b355fc97616ff20e1

Summary:
The cmake globbing then excluding strategy implies that if the directory
in which we are compiling has a folder named `build` on its path like `/home/alice/project/build/folly/...`, everything breaks.
Note that it is the same for `tools` and `test`, I also fixed the tools one, but the test once has many files.... Using a file list would be the real solution.
Closes https://github.com/facebook/folly/pull/815

Reviewed By: simpkins

Differential Revision: D7624035

Pulled By: yfeldblum

fbshipit-source-id: a3f1d2f82e55e070d13acc5c394d8cfdfabeb7ed

Summary:
The existing histogram approach for estimating quantiles is inadequate for common use cases. This diff introduces TDigests for estimating quantiles of streaming values.

The current histogram approach suffers from two issues:
  - The user needs to know something about the universe of values, U, and the underlying distribution in order to get reasonably accurate values
  - Because the histogram is not biased, estimating tail quantiles such as p99.9 requires a large amount of memory.

t-digests (https://github.com/tdunning/t-digest/blob/master/docs/t-digest-paper/histo.pdf) are biased digests that allow for accurate estimates of tail quantiles, while using a small amount of memory and without requiring the user to know anything about U.

The scaling function in the paper is slow, because it uses arcsin. This approach uses a sqrt function instead. Details of why this works in the comments of the TDigest file.

Reviewed By: simpkins

Differential Revision: D7512432

fbshipit-source-id: 01460433ec7380fed88e5e942ef15f032dd794bb

Summary: [Folly] Fix `constexpr` predicate names, which have embarrassing typos.

Reviewed By: igorsugak

Differential Revision: D7605352

fbshipit-source-id: e04a87fd375f09472b020380bf446c7236a39e51

Summary:
Fix broken Android build

(Note: this ignores all push blocking failures!)

Reviewed By: michalgr

Differential Revision: D7606076

fbshipit-source-id: 0cf0426a34cf62b045acb932d42a8e4a3cd5da71

Summary:
When trying to compile `folly/experimental/exception_tracer` with gcc-7.2, I get the following error:

```
ExceptionCounterLib.cpp: In instantiation of '{anonymous}::throwHandler(void*, std::type_info*, void (*)(void*))::<lambda(auto:9&)> [with auto:9 = std::unordered_map<long unsigned int, folly::exception_tracer::ExceptionStats>]':
../../../folly/Synchronized.h:162:20:   required from 'auto folly::SynchronizedBase<Subclass, (folly::detail::MutexLevel)1>::withWLock(Function&&) [with Function = {anonymous}::throwHandler(void*, std::type_info*, void (*)(void*))::<lambda(auto:9&)>; Subclass = folly::Synchronized<std::unordered_map<long unsigned int, folly::exception_tracer::ExceptionStats>, folly::RWSpinLock>]'
ExceptionCounterLib.cpp:132:4:   required from here
ExceptionCounterLib.cpp:127:21: error: uninitialized variable 'info' in 'constexpr' function
       ExceptionInfo info;
                     ^~~~
In file included from ../../../folly/experimental/exception_tracer/ExceptionCounterLib.h:22:0,
                 from ExceptionCounterLib.cpp:16:
../../../folly/experimental/exception_tracer/ExceptionTracer.h:30:8: note: 'struct folly::exception_tracer::ExceptionInfo' has no user-provided default constructor
 struct ExceptionInfo {
        ^~~~~~~~~~~~~
../../../folly/experimental/exception_tracer/ExceptionTracer.h:31:25: note: and the implicitly-defined constructor does not initialize 'const std::type_info* folly::exception_tracer::ExceptionInfo::type'
   const std::type_info* type;
                         ^~~~
```

Fixed by initializing `ExceptionInfo::type`.

Compiling with gcc 7.2 now works.
Closes https://github.com/facebook/folly/pull/812

Reviewed By: Orvid

Differential Revision: D7598341

Pulled By: yfeldblum

fbshipit-source-id: 0a8859b6d5f174484c8f2148de59a2a592dc2b25

Summary: [Folly] Rename `IOBufEqual` to `IOBufEqualTo` to correspond with the standard naming of `std::equal_to`.

Reviewed By: Orvid

Differential Revision: D7596716

fbshipit-source-id: 2e87aa4b62a002520bdd53b5b7eaba7d9bd822da

Summary:
in Linux environment, `find_package(gflass)` searches `Findgflags.cmake`.
And it cannot find  https://github.com/facebook/folly/blob/master/CMake/FindGFlags.cmake , because linux is case-sensitive environment in filenames and cause error.

```
CMake Error at CMake/folly-deps.cmake:34 (message):
  Unable to determine the target name for the GFlags package.
Call Stack (most recent call first):
  CMakeLists.txt:65 (include)
```

For linux programmers, this line should find `FindGFlags.cmake` file which exists in the same directory.
Closes https://github.com/facebook/folly/pull/805

Reviewed By: yfeldblum

Differential Revision: D7505908

Pulled By: Orvid

fbshipit-source-id: c30097a25569d293df9a1bfecbee84cece260306

Summary:
[Folly] Function objects for performing `constexpr` comparisons for C++11 or gcc49.

After upgrading to C++14 and dropping support for C++11, these may be removed because the corresponding function objects in the C++14 standard library are `constexpr`-invocable.

Reviewed By: Orvid

Differential Revision: D7590351

fbshipit-source-id: a8702115a66836aff25761f374b8a2d7dbe12074