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std: Move elf TLS to sys::fast_thread_local

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This commit is contained in:
Brian Anderson 2016-09-30 20:13:58 +00:00
parent ac968c4664
commit 568840707c
5 changed files with 171 additions and 163 deletions
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167
src/libstd/sys/unix/fast_thread_local.rs Normal file
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@ -0,0 +1,167 @@
// Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![cfg(target_thread_local)]
#![unstable(feature = "thread_local_internals", issue = "0")]
use cell::{Cell, UnsafeCell};
use intrinsics;
use ptr;
pub struct Key<T> {
inner: UnsafeCell<Option<T>>,
// Metadata to keep track of the state of the destructor. Remember that
// these variables are thread-local, not global.
dtor_registered: Cell<bool>,
dtor_running: Cell<bool>,
}
unsafe impl<T> ::marker::Sync for Key<T> { }
impl<T> Key<T> {
pub const fn new() -> Key<T> {
Key {
inner: UnsafeCell::new(None),
dtor_registered: Cell::new(false),
dtor_running: Cell::new(false)
}
}
pub fn get(&'static self) -> Option<&'static UnsafeCell<Option<T>>> {
unsafe {
if intrinsics::needs_drop::<T>() && self.dtor_running.get() {
return None
}
self.register_dtor();
}
Some(&self.inner)
}
unsafe fn register_dtor(&self) {
if !intrinsics::needs_drop::<T>() || self.dtor_registered.get() {
return
}
register_dtor(self as *const _ as *mut u8,
destroy_value::<T>);
self.dtor_registered.set(true);
}
}
#[cfg(any(target_os = "linux", target_os = "fuchsia"))]
unsafe fn register_dtor_fallback(t: *mut u8, dtor: unsafe extern fn(*mut u8)) {
// The fallback implementation uses a vanilla OS-based TLS key to track
// the list of destructors that need to be run for this thread. The key
// then has its own destructor which runs all the other destructors.
//
// The destructor for DTORS is a little special in that it has a `while`
// loop to continuously drain the list of registered destructors. It
// *should* be the case that this loop always terminates because we
// provide the guarantee that a TLS key cannot be set after it is
// flagged for destruction.
use sys_common::thread_local as os;
static DTORS: os::StaticKey = os::StaticKey::new(Some(run_dtors));
type List = Vec<(*mut u8, unsafe extern fn(*mut u8))>;
if DTORS.get().is_null() {
let v: Box<List> = box Vec::new();
DTORS.set(Box::into_raw(v) as *mut u8);
}
let list: &mut List = &mut *(DTORS.get() as *mut List);
list.push((t, dtor));
unsafe extern fn run_dtors(mut ptr: *mut u8) {
while !ptr.is_null() {
let list: Box<List> = Box::from_raw(ptr as *mut List);
for &(ptr, dtor) in list.iter() {
dtor(ptr);
}
ptr = DTORS.get();
DTORS.set(ptr::null_mut());
}
}
}
// Since what appears to be glibc 2.18 this symbol has been shipped which
// GCC and clang both use to invoke destructors in thread_local globals, so
// let's do the same!
//
// Note, however, that we run on lots older linuxes, as well as cross
// compiling from a newer linux to an older linux, so we also have a
// fallback implementation to use as well.
//
// Due to rust-lang/rust#18804, make sure this is not generic!
#[cfg(target_os = "linux")]
unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern fn(*mut u8)) {
use mem;
use libc;
extern {
#[linkage = "extern_weak"]
static __dso_handle: *mut u8;
#[linkage = "extern_weak"]
static __cxa_thread_atexit_impl: *const libc::c_void;
}
if !__cxa_thread_atexit_impl.is_null() {
type F = unsafe extern fn(dtor: unsafe extern fn(*mut u8),
arg: *mut u8,
dso_handle: *mut u8) -> libc::c_int;
mem::transmute::<*const libc::c_void, F>(__cxa_thread_atexit_impl)
(dtor, t, &__dso_handle as *const _ as *mut _);
return
}
register_dtor_fallback(t, dtor);
}
// OSX's analog of the above linux function is this _tlv_atexit function.
// The disassembly of thread_local globals in C++ (at least produced by
// clang) will have this show up in the output.
#[cfg(target_os = "macos")]
unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern fn(*mut u8)) {
extern {
fn _tlv_atexit(dtor: unsafe extern fn(*mut u8),
arg: *mut u8);
}
_tlv_atexit(dtor, t);
}
// Just use the thread_local fallback implementation, at least until there's
// a more direct implementation.
#[cfg(target_os = "fuchsia")]
unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern fn(*mut u8)) {
register_dtor_fallback(t, dtor);
}
pub unsafe extern fn destroy_value<T>(ptr: *mut u8) {
let ptr = ptr as *mut Key<T>;
// Right before we run the user destructor be sure to flag the
// destructor as running for this thread so calls to `get` will return
// `None`.
(*ptr).dtor_running.set(true);
// The OSX implementation of TLS apparently had an odd aspect to it
// where the pointer we have may be overwritten while this destructor
// is running. Specifically if a TLS destructor re-accesses TLS it may
// trigger a re-initialization of all TLS variables, paving over at
// least some destroyed ones with initial values.
//
// This means that if we drop a TLS value in place on OSX that we could
// revert the value to its original state halfway through the
// destructor, which would be bad!
//
// Hence, we use `ptr::read` on OSX (to move to a "safe" location)
// instead of drop_in_place.
if cfg!(target_os = "macos") {
ptr::read((*ptr).inner.get());
} else {
ptr::drop_in_place((*ptr).inner.get());
}
}

1
src/libstd/sys/unix/mod.rs
View File

@ -38,6 +38,7 @@ pub mod backtrace;
pub mod condvar; pub mod condvar;
pub mod env; pub mod env;
pub mod ext; pub mod ext;
pub mod fast_thread_local;
pub mod fd; pub mod fd;
pub mod fs; pub mod fs;
pub mod memchr; pub mod memchr;

163
src/libstd/thread/local.rs
View File

@ -166,8 +166,8 @@ macro_rules! __thread_local_inner {
{ {
#[thread_local] #[thread_local]
#[cfg(target_thread_local)] #[cfg(target_thread_local)]
static __KEY: $crate::thread::__ElfLocalKeyInner<$t> = static __KEY: $crate::thread::__FastLocalKeyInner<$t> =
$crate::thread::__ElfLocalKeyInner::new(); $crate::thread::__FastLocalKeyInner::new();
#[cfg(not(target_thread_local))] #[cfg(not(target_thread_local))]
static __KEY: $crate::thread::__OsLocalKeyInner<$t> = static __KEY: $crate::thread::__OsLocalKeyInner<$t> =
@ -310,165 +310,6 @@ impl<T: 'static> LocalKey<T> {
} }
} }
#[cfg(target_thread_local)]
#[doc(hidden)]
pub mod elf {
use cell::{Cell, UnsafeCell};
use intrinsics;
use ptr;
pub struct Key<T> {
inner: UnsafeCell<Option<T>>,
// Metadata to keep track of the state of the destructor. Remember that
// these variables are thread-local, not global.
dtor_registered: Cell<bool>,
dtor_running: Cell<bool>,
}
unsafe impl<T> ::marker::Sync for Key<T> { }
impl<T> Key<T> {
pub const fn new() -> Key<T> {
Key {
inner: UnsafeCell::new(None),
dtor_registered: Cell::new(false),
dtor_running: Cell::new(false)
}
}
pub fn get(&'static self) -> Option<&'static UnsafeCell<Option<T>>> {
unsafe {
if intrinsics::needs_drop::<T>() && self.dtor_running.get() {
return None
}
self.register_dtor();
}
Some(&self.inner)
}
unsafe fn register_dtor(&self) {
if !intrinsics::needs_drop::<T>() || self.dtor_registered.get() {
return
}
register_dtor(self as *const _ as *mut u8,
destroy_value::<T>);
self.dtor_registered.set(true);
}
}
#[cfg(any(target_os = "linux", target_os = "fuchsia"))]
unsafe fn register_dtor_fallback(t: *mut u8, dtor: unsafe extern fn(*mut u8)) {
// The fallback implementation uses a vanilla OS-based TLS key to track
// the list of destructors that need to be run for this thread. The key
// then has its own destructor which runs all the other destructors.
//
// The destructor for DTORS is a little special in that it has a `while`
// loop to continuously drain the list of registered destructors. It
// *should* be the case that this loop always terminates because we
// provide the guarantee that a TLS key cannot be set after it is
// flagged for destruction.
use sys_common::thread_local as os;
static DTORS: os::StaticKey = os::StaticKey::new(Some(run_dtors));
type List = Vec<(*mut u8, unsafe extern fn(*mut u8))>;
if DTORS.get().is_null() {
let v: Box<List> = box Vec::new();
DTORS.set(Box::into_raw(v) as *mut u8);
}
let list: &mut List = &mut *(DTORS.get() as *mut List);
list.push((t, dtor));
unsafe extern fn run_dtors(mut ptr: *mut u8) {
while !ptr.is_null() {
let list: Box<List> = Box::from_raw(ptr as *mut List);
for &(ptr, dtor) in list.iter() {
dtor(ptr);
}
ptr = DTORS.get();
DTORS.set(ptr::null_mut());
}
}
}
// Since what appears to be glibc 2.18 this symbol has been shipped which
// GCC and clang both use to invoke destructors in thread_local globals, so
// let's do the same!
//
// Note, however, that we run on lots older linuxes, as well as cross
// compiling from a newer linux to an older linux, so we also have a
// fallback implementation to use as well.
//
// Due to rust-lang/rust#18804, make sure this is not generic!
#[cfg(target_os = "linux")]
unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern fn(*mut u8)) {
use mem;
use libc;
extern {
#[linkage = "extern_weak"]
static __dso_handle: *mut u8;
#[linkage = "extern_weak"]
static __cxa_thread_atexit_impl: *const libc::c_void;
}
if !__cxa_thread_atexit_impl.is_null() {
type F = unsafe extern fn(dtor: unsafe extern fn(*mut u8),
arg: *mut u8,
dso_handle: *mut u8) -> libc::c_int;
mem::transmute::<*const libc::c_void, F>(__cxa_thread_atexit_impl)
(dtor, t, &__dso_handle as *const _ as *mut _);
return
}
register_dtor_fallback(t, dtor);
}
// OSX's analog of the above linux function is this _tlv_atexit function.
// The disassembly of thread_local globals in C++ (at least produced by
// clang) will have this show up in the output.
#[cfg(target_os = "macos")]
unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern fn(*mut u8)) {
extern {
fn _tlv_atexit(dtor: unsafe extern fn(*mut u8),
arg: *mut u8);
}
_tlv_atexit(dtor, t);
}
// Just use the thread_local fallback implementation, at least until there's
// a more direct implementation.
#[cfg(target_os = "fuchsia")]
unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern fn(*mut u8)) {
register_dtor_fallback(t, dtor);
}
pub unsafe extern fn destroy_value<T>(ptr: *mut u8) {
let ptr = ptr as *mut Key<T>;
// Right before we run the user destructor be sure to flag the
// destructor as running for this thread so calls to `get` will return
// `None`.
(*ptr).dtor_running.set(true);
// The OSX implementation of TLS apparently had an odd aspect to it
// where the pointer we have may be overwritten while this destructor
// is running. Specifically if a TLS destructor re-accesses TLS it may
// trigger a re-initialization of all TLS variables, paving over at
// least some destroyed ones with initial values.
//
// This means that if we drop a TLS value in place on OSX that we could
// revert the value to its original state halfway through the
// destructor, which would be bad!
//
// Hence, we use `ptr::read` on OSX (to move to a "safe" location)
// instead of drop_in_place.
if cfg!(target_os = "macos") {
ptr::read((*ptr).inner.get());
} else {
ptr::drop_in_place((*ptr).inner.get());
}
}
}
#[doc(hidden)] #[doc(hidden)]
pub mod os { pub mod os {
use cell::{Cell, UnsafeCell}; use cell::{Cell, UnsafeCell};

2
src/libstd/thread/mod.rs
View File

@ -183,7 +183,7 @@ pub use self::local::{LocalKey, LocalKeyState};
#[unstable(feature = "libstd_thread_internals", issue = "0")] #[unstable(feature = "libstd_thread_internals", issue = "0")]
#[cfg(target_thread_local)] #[cfg(target_thread_local)]
#[doc(hidden)] pub use self::local::elf::Key as __ElfLocalKeyInner; #[doc(hidden)] pub use sys::fast_thread_local::Key as __FastLocalKeyInner;
#[unstable(feature = "libstd_thread_internals", issue = "0")] #[unstable(feature = "libstd_thread_internals", issue = "0")]
#[doc(hidden)] pub use self::local::os::Key as __OsLocalKeyInner; #[doc(hidden)] pub use self::local::os::Key as __OsLocalKeyInner;

1
src/tools/tidy/src/pal.rs
View File

@ -69,7 +69,6 @@ const EXCEPTION_PATHS: &'static [&'static str] = &[
"src/libstd/io/stdio.rs", "src/libstd/io/stdio.rs",
"src/libstd/num/f32.rs", "src/libstd/num/f32.rs",
"src/libstd/num/f64.rs", "src/libstd/num/f64.rs",
"src/libstd/thread/local.rs",
"src/libstd/sys/common/mod.rs", "src/libstd/sys/common/mod.rs",
"src/libstd/sys/common/net.rs", "src/libstd/sys/common/net.rs",
"src/libstd/sys/common/util.rs", "src/libstd/sys/common/util.rs",