Summary:
The deps for Fedora in the public README are a little out of date.  Add /
update some.

Reviewed By: yfeldblum

Differential Revision: D22951514

fbshipit-source-id: 645af3df1b71dcdab06408d73d99c34c482ea534

Summary:
When we do the context switch onto the fiber, the stack frame points back to
the main context stack. While the fiber is running, this allows backtraces to
continue back onto the main context. When the fiber is suspended, we execute
code on the main context's stack, the pointers to this stack are now garbage,
backtracing in gdb runs into problems, such as garbage frames, gdb
crashes, and occasional cycles.

The fix here is to write a 0 to the saved return address in the last frame, when a fiber suspends.
gdb detects this and stops the trace
  #38 folly::fibers::FiberManager::activateFiber(folly::fibers::Fiber*) (this=0x0, fiber=0x0) at folly/fibers/FiberManagerInternal-inl.h:82
  #39 folly::fibers::FiberManager::runReadyFiber(folly::fibers::Fiber*) (this=0x0, fiber=0x0) at folly/fibers/FiberManagerInternal-inl.h:127
  #40 0x0000000000000000 in  ()

I gated the fix to linux since I'm not sure about the ABI for other platforms.

Reviewed By: yfeldblum

Differential Revision: D22774189

fbshipit-source-id: 2d4ad67a4a01bebc4ff1f9c285f6e3e95d13432c

Summary:
- Move to the newer and forward moving libzstd-dev
https://packages.ubuntu.com/search?suite=default&section=all&arch=any&keywords=libzstd&searchon=names

Reviewed By: wez

Differential Revision: D22981784

fbshipit-source-id: 3647357aad60f2335ea494c35c174e9ffec61346

Summary: The find path reads a node that the insert path writes; they need to have acquire/release semantics due to the node being allocated on the fly.

Reviewed By: yfeldblum, magedm

Differential Revision: D22937394

fbshipit-source-id: c1497ed1764cd43e396bc520e9b716cdfe29e5ca

Summary:
Redirecting stdout means that ninja/cmake won't act as if it's invoked
interactively, ie: it will buffer the output, show every single files being
compiled (instead of just a line or progress), etc. This results in a fairly
janky UX when getdeps is used on the command line. By not redirecting stdout,
we get immediate feedback about the tests being run, and the files being
compiled.

Reviewed By: wez

Differential Revision: D22967815

fbshipit-source-id: 872ddbf421065686c384a3a876d0acb8832baf2e

Summary: [Folly] Prefer `std::condition_t` vs preprocessor in `AsyncSocket`.

Reviewed By: bschlinker, lnicco

Differential Revision: D22975614

fbshipit-source-id: 562d1b794ec3dbab538ad507b2ec5d0fe07c7757

Summary: [Folly] Let `exceptionStr` peek into unknown exception types when building with libstdc++ via `std::exception_ptr::__cxa_exception_type()`.

Reviewed By: ot, luciang

Differential Revision: D22521812

fbshipit-source-id: b75811ed4159df81e651c5df1386c406f6ac6d60

Summary: Generic code taking in a `Task<void|T>` cannot easily forward the result without throwing exceptions because the `return_value` overload taking a `Try` cannot be added to `Task<void>` which already has `return_void`. Instead we use `yield_value` as we did with `co_error` to make the desired generic code possible.

Reviewed By: lewissbaker

Differential Revision: D22934887

fbshipit-source-id: ec50de5832f9038d92749bdde2c1d43244288a3c

Summary: We know ahead of time the size of this list, so may as well pre-allocate space for it

Reviewed By: yfeldblum

Differential Revision: D22838412

fbshipit-source-id: 7d70495fe0910e65dfea49fe7baf675308ab9331

Summary: If the binary is compiled as PIE, such as in the case of TSAN, the kStringValue symbol's value, which is an address that in turn points to the "coconuts" character array, may be stored as 0 in the binary file, and rely on the dynamic linker to relocate at loading time. The corresponding relocation entry (in the .rela.dyn section) contains the relative offset instead. We do not seem to have implemented parsing of the relocation section, so this diff changes the test to be more lenient, and upon seeing a zero will just verify the address of the symbol against the live binary.

Reviewed By: yfeldblum

Differential Revision: D22782080

fbshipit-source-id: ffbfc7c23b84865fb29bbfb782feb896d687594b

Summary: Add the ability to set the event EventRecvmsgCallback

Reviewed By: danobi

Differential Revision: D22959687

fbshipit-source-id: 274cecf4ab4b8015d5e7e725c7e899f603cea7a0

Summary: [Folly] Add missing include in `folly/ExceptionString.cpp`.

Reviewed By: ot, luciang

Differential Revision: D22529764

fbshipit-source-id: 91af74023fd81b1882a19889fd92fda4e1bdfcc7

Summary:
Two issues:
 - Executor not properly shutdown before destruction
 - Shadow stack overflow due to TSAN not handling fibers correctly. For this we just reduce the number of tasks for now; the proper fix would be likely quite involved and it's not clear whether it's worth it at this point since I think it only affects diagnostic messages that TSAN prints.

Reviewed By: yfeldblum

Differential Revision: D22901657

fbshipit-source-id: 833454e6f54ab6fc7c53333157197345e8d887e2

Summary:
Environment variable WITH_ASAN can be set to enable building
 with ASAN options.

 Ran into issues with getdeps.py extensions P137131160.
 Once that is resolved will do away with the ENV approach

 Requires building folly lib also with ASAN to avoid linking issues

Reviewed By: shri-khare

Differential Revision: D22860508

fbshipit-source-id: 48dea49378319972894f69b11bac6fa63ee20db9

Summary: This spin lock is not required, and guards quite a complex region that could easily fallback to the slow path

Reviewed By: andriigrynenko

Differential Revision: D22839268

fbshipit-source-id: 045a3562a2d4358b4c95e155a4b9958b2b7f67d4

Summary:
Two ordering issues:

setTreeNode cannot store the node as relaxed, because the node is newly allocated before storing, and if another thread gets the node pointer value, relaxed ordering cannot guarantee that the node has been fully initialized before it.

There are two ways this node can be read, one via optimisticReadValue, which loads with memory_order_acquired, which would now correctly synchronize with the release; the other is readValue, which I think was intended to be used only when the lock corresponding to the node is held, but there is one case on line 781 in forceInsert where we fail to acquire the lock but it looks like we want to retry unless we're out of capacity (on a best effort basis) and therefore we call readValue to check the capacity (on a best effort basis), so it looks as if memory_order_relaxed is okay, but it is not, because the node is a pointer that may not be fully initialized with relaxed ordering. So I'm changing that to memory_order_acquire as well.

In general it's not really valid to use relaxed ordering if the value is a pointer and the pointee is allocated on the fly.

Reviewed By: yfeldblum

Differential Revision: D22936002

fbshipit-source-id: 1c8a000b6033e4a81df5f9a5e850cfe350dbeb15

Summary: Remove TSAN code that caused an assert

Reviewed By: andriigrynenko

Differential Revision: D22925613

fbshipit-source-id: 67cf634ccd29453a6e399951b8bf541a2c471104

Summary:
The SymbolizePrinter classes are portable to any unix, so split them
into their own target.

Reviewed By: yfeldblum, luciang

Differential Revision: D22883912

fbshipit-source-id: 3bce6d6584182b818bf803da187eae56477bac8a

Summary:
In the interest of using SignalHandler on macOS, which does not use
ELF, break some dependencies and split the targets.

Reviewed By: yfeldblum, luciang

Differential Revision: D22883896

fbshipit-source-id: e576b6e1684522fc1665c864780faea882d0263a

Summary: The memory ordering when loading the `waiter_` atomic must be at least memory_order_acquire to ensure that anything sequenced after timedWaitThread happens before the corresponding post call. In fact, this is already the memory ordering used in the non-timed version Baton::waitThread.

Differential Revision: D22901656

fbshipit-source-id: 8e8156bdfda02d6b26565b91054ef3cc59a28e8a

Summary: Add support for TimerFD async recv

Reviewed By: kevin-vigor

Differential Revision: D22860507

fbshipit-source-id: e1afc9d72608f5a574413e1230d6665420240af7

Summary: Add APIs to disable rx/tx checksum for UDP over IPV6

Differential Revision: D22487077

fbshipit-source-id: 22af21b108e84782ec0a76ccbc49eaafa73bd266

Summary: Mcrouter has a logger thread which queries the fiber manager for 3 stats; these stats are non-atomic and therefore this causes a race. This diff applies a simple fix to make these atomic. It does not feel like this is the best fix though, so let me know if anyone has ideas for a better fix. It feels that stats should be provided some other way (rather than a bunch of atomics)...

Reviewed By: yfeldblum

Differential Revision: D22878457

fbshipit-source-id: f17544b38836c454162b83cfa570c90c5e7e6b9a

Summary:
port serdes object type is introduced in 1.5.2

upgrading tp2 sai dependency to 1.5.2

note that for first time, oss build failed, i had to back out removing http_proxy and https_proxy indicated here - D17429928

Differential Revision: D22888202

fbshipit-source-id: c0f90b1caa01603d25b0559188ae961df1dd13d5

Summary: TSAN has a limit of 8128 threads.

Reviewed By: yfeldblum

Differential Revision: D22888242

fbshipit-source-id: 12b78e11145de433dfa31ea1480649af7f8dac57

Summary: Simplify the interface as the touch(), remove() methods are not needed now.

Reviewed By: therealgymmy

Differential Revision: D22547658

fbshipit-source-id: 6d5c799fb21cb4cb6ee20203c820f4d6ff7e8255

Summary: Like ASAN, TSAN also maps large memory regions. So disable the rlimit for TSAN as well.

Differential Revision: D22743326

fbshipit-source-id: 5023b66f1526894c77e6c693a2481f6ade388b9e

Summary: [Folly] Avoid `std::forward` in `folly/futures/` since function template instantiation is expensive at compile time and `std::forward` is, when used correctly, nothing more than library sugar for straightforward syntax.

Reviewed By: LeeHowes

Differential Revision: D22673234

fbshipit-source-id: f88bc8c8aa13797ae6eccf1a421a47ff135589e1

Summary:
Some of the CHECKs and DCHECKs in F14 are often tripped by users
that write to an F14 map or set from multiple threads without proper
concurrency control.  This diff adds a message to those locations that
suggests that they may have a race condition.

Reviewed By: yfeldblum

Differential Revision: D22826369

fbshipit-source-id: 8d5e96feea4dbb8dda404980d9a9d3412fb2eb64

Summary:
See task T70610458 description for the TSAN error reported.

The scenario that can trigger this race condition is:
 * Thread A has a ThreadEntryNode N whose `next` points to thread B's ThreadEntry.
 * Thread B exits, which causes it to delete its ThreadEntry and all its nodes; therefore writing `N->next = <the next entry after B>`.
 * At the same time, thread A accesses the thread local corresponding to N; when checking whether the ThreadEntryNode is already added to the linked list, it checks whether the `next` pointer is null; this read races with the above write.

Even though this is a technically a race condition, it is unlikely to actually trigger any negative effect in practice, because at thread exit, the overwrite of `N->next = ...` will never assign a nullptr, so it will never affect the outcome of `if (!next)` in thread A. Only the thread that owns the ThreadEntryNode has the ability to change between `next == nullptr` and `next != nullptr`. (The former is called "zero" in the code). Nonetheless, C++ says "race condition leads to undefined behavior", so it's still good to fix...

It's not clear what the best way to fix this is. Here I've presented one fix, which is to introduce another field in ThreadEntryNode that is private to the thread and simply indicates whether the node is zero; this field is strictly accessed by only the owning thread and therefore will not cause a race condition. I used a bit in `id` to not increase memory consumption, but maybe that's not important - I don't know. I'm also unsure about the performance implications.

Let me know if anyone has different ideas; I'm very open to suggestions here.

Reviewed By: yfeldblum

Differential Revision: D22743031

fbshipit-source-id: 12722ca241a224b546a0f6763b125e922813c844

Summary: Turned it into a thread_local instead. Only affects tests.

Reviewed By: yfeldblum

Differential Revision: D22744469

fbshipit-source-id: cbe8263d560f5abad27c7e61b1963aecf090a94e

Summary:
See RefCountTest.cpp for a newly added test. When one thread is decrementing a local refcount and another thread is decrementing a global refcount, and the global decrement results in global zero, the second thread can reasonably expect to be able to safely destroy the refcount object. However, a memory ordering issue in LocalRefCount::collect() causes TSAN to detect a write-delete race condition on the inUpdate_ variable (though that variable is not the cause of the issue).

This diff changes collect() to use memory_order_acquire so that upon reading false, collect() may exit while assuming that all memory accesses in update() are complete. This way, any memory accesses (such as a read of refCount_.state_ in update()) happen before a delete of the whole TLRefCount like so:

 - A memory access in update() is sequenced before the release store of false into inUpdate_ at the SCOPE_EXIT of the function,
 - which synchronizes with the acquire load at the end of collect()
 - which is sequenced before the deletion that can only happen after collect()

Without this diff, the second relationship above is broken and TSAN complains.

I also updated the comment on top of inUpdate_ to better reflect the purpose. I couldn't understand the original comment (which seems to suggest it's related to refcount *correctness* rather than a write-delete race), but maybe I missed something there.

Reviewed By: yfeldblum

Differential Revision: D22805717

fbshipit-source-id: 34cf72676760526ba457f939e307ed03dc722528

Summary:
we do have some periodic maintentenance tasks... if those are initialized
lazily on a requests handling path, they  will capture current rctx and keep it
it alive forever.

Reviewed By: yfeldblum

Differential Revision: D22859344

fbshipit-source-id: 3655d874dee22aaf74b4d80631d4a58e83539752

Summary: AppBytesWitten was no longer updated correctly for AsyncSSLSocket, fix this.

Reviewed By: bschlinker

Differential Revision: D22847139

fbshipit-source-id: 8cabb9883e5ad64c49a283a0d83b8087def4d5ae

Summary:
Currently when context string is "", we will still append whitespace to log header. This looks like:
```
I0729 17:36:53.249270 438847 ThriftServerEventHandler.cpp:21 ] Sampling servers
```
which is less readable compared to
```
I0729 17:36:53.249270 438847 ThriftServerEventHandler.cpp:21] Sampling servers
```
. Ideally empty context string should mean "there's no context string to report here", so we should not put an extra delimiter in such case.

Reviewed By: simpkins

Differential Revision: D22835634

fbshipit-source-id: c7fc6de4036050eac3b7d16bf607c637d1394c44

Reviewed By: yfeldblum

Differential Revision: D22843001

fbshipit-source-id: 55f48de90f16c53983ea94c8e1102c5b33e25195

Summary:
I'm using AsyncPipe heavily in D22593723. At one iteration I needed to assign with move a holding object and it wouldn't compile because the operator doesn't return any value

Here's the error: `folly/experimental/coro/AsyncPipe.h:54:3: error: control reaches end of non-void function [-Werror,-Wreturn-type]`

Reviewed By: yfeldblum

Differential Revision: D22593724

fbshipit-source-id: 53f27b95c1dff0068a375291d4ee6f445f892dd9

Summary: [Folly] Move an `exception_ptr` in `exceptionStr`, which should be ever-so-slightly cheaper than copying it since that may avoid atomic refcount operations. It's not much cheaper overall because the throw/catch machinery remains expensive.

Reviewed By: ot, luciang

Differential Revision: D22529858

fbshipit-source-id: 7e5d4ec5c1ca601a766c63133ae759651ae7be85

Summary: [Folly] Outline `exceptionStr` function bodies and move them to the `.cpp`.

Reviewed By: ot, luciang

Differential Revision: D22529702

fbshipit-source-id: 165c14009f224e86e63b3a3126c8b837cf3793f5

Summary: [Folly] Skip the safe-assert dep on FileUtil since it really needs only the combinators.

Reviewed By: Orvid

Differential Revision: D22699899

fbshipit-source-id: 73485439e397c10210d09eacbb38116e3e0a50a0