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Consolidate local_data implementations, and cleanup

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This moves all local_data stuff into the `local_data` module and only that
module alone. It also removes a fair amount of "super-unsafe" code in favor of
just vanilla code generated by the compiler at the same time.

Closes #8113
This commit is contained in:
Alex Crichton 2013-08-10 20:06:39 -07:00
parent 578e680477
commit 06a7195e9e
5 changed files with 476 additions and 558 deletions
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678
src/libstd/local_data.rs
View File

@ -39,11 +39,11 @@
*/
use cast;
use libc;
use prelude::*;
use task::local_data_priv::*;
#[cfg(test)] use task;
use rt::task::{Task, LocalStorage};
use util;
/**
* Indexes a task-local data slot. This pointer is used for comparison to
@ -60,263 +60,509 @@
pub enum KeyValue<T> { Key }
/**
* Remove a task-local data value from the table, returning the
* reference that was originally created to insert it.
*/
trait LocalData {}
impl<T: 'static> LocalData for T {}
// The task-local-map stores all TLS information for the currently running task.
// It is stored as an owned pointer into the runtime, and it's only allocated
// when TLS is used for the first time. This map must be very carefully
// constructed because it has many mutable loans unsoundly handed out on it to
// the various invocations of TLS requests.
//
// One of the most important operations is loaning a value via `get` to a
// caller. In doing so, the slot that the TLS entry is occupying cannot be
// invalidated because upon returning it's loan state must be updated. Currently
// the TLS map is a vector, but this is possibly dangerous because the vector
// can be reallocated/moved when new values are pushed onto it.
//
// This problem currently isn't solved in a very elegant way. Inside the `get`
// function, it internally "invalidates" all references after the loan is
// finished and looks up into the vector again. In theory this will prevent
// pointers from being moved under our feet so long as LLVM doesn't go too crazy
// with the optimizations.
//
// n.b. If TLS is used heavily in future, this could be made more efficient with
// a proper map.
#[doc(hidden)]
pub type Map = ~[Option<(*libc::c_void, TLSValue, LoanState)>];
type TLSValue = ~LocalData;
// Gets the map from the runtime. Lazily initialises if not done so already.
unsafe fn get_local_map() -> &mut Map {
use rt::local::Local;
let task: *mut Task = Local::unsafe_borrow();
match &mut (*task).storage {
// If the at_exit function is already set, then we just need to take
// a loan out on the TLS map stored inside
&LocalStorage(Some(ref mut map_ptr)) => {
return map_ptr;
}
// If this is the first time we've accessed TLS, perform similar
// actions to the oldsched way of doing things.
&LocalStorage(ref mut slot) => {
*slot = Some(~[]);
match *slot {
Some(ref mut map_ptr) => { return map_ptr }
None => abort()
}
}
}
}
#[deriving(Eq)]
enum LoanState {
NoLoan, ImmLoan, MutLoan
}
impl LoanState {
fn describe(&self) -> &'static str {
match *self {
NoLoan => "no loan",
ImmLoan => "immutable",
MutLoan => "mutable"
}
}
}
fn key_to_key_value<T: 'static>(key: Key<T>) -> *libc::c_void {
unsafe { cast::transmute(key) }
}
/// Removes a task-local value from task-local storage. This will return
/// Some(value) if the key was present in TLS, otherwise it will return None.
///
/// A runtime assertion will be triggered it removal of TLS value is attempted
/// while the value is still loaned out via `get` or `get_mut`.
pub fn pop<T: 'static>(key: Key<T>) -> Option<T> {
unsafe { local_pop(Handle::new(), key) }
let map = unsafe { get_local_map() };
let key_value = key_to_key_value(key);
for entry in map.mut_iter() {
match *entry {
Some((k, _, loan)) if k == key_value => {
if loan != NoLoan {
fail!("TLS value cannot be removed because it is currently \
borrowed as %s", loan.describe());
}
// Move the data out of the `entry` slot via util::replace.
// This is guaranteed to succeed because we already matched
// on `Some` above.
let data = match util::replace(entry, None) {
Some((_, data, _)) => data,
None => abort()
};
// Move `data` into transmute to get out the memory that it
// owns, we must free it manually later.
let (_vtable, box): (uint, ~~T) = unsafe {
cast::transmute(data)
};
// Now that we own `box`, we can just move out of it as we would
// with any other data.
return Some(**box);
}
_ => {}
}
}
return None;
}
/**
* Retrieve a task-local data value. It will also be kept alive in the
* table until explicitly removed.
*/
/// Retrieves a value from TLS. The closure provided is yielded `Some` of a
/// reference to the value located in TLS if one exists, or `None` if the key
/// provided is not present in TLS currently.
///
/// It is considered a runtime error to attempt to get a value which is already
/// on loan via the `get_mut` method provided.
pub fn get<T: 'static, U>(key: Key<T>, f: &fn(Option<&T>) -> U) -> U {
unsafe { local_get(Handle::new(), key, f) }
get_with(key, ImmLoan, f)
}
/**
* Retrieve a mutable borrowed pointer to a task-local data value.
*/
/// Retrieves a mutable value from TLS. The closure provided is yielded `Some`
/// of a reference to the mutable value located in TLS if one exists, or `None`
/// if the key provided is not present in TLS currently.
///
/// It is considered a runtime error to attempt to get a value which is already
/// on loan via this or the `get` methods. This is similar to how it's a runtime
/// error to take two mutable loans on an `@mut` box.
pub fn get_mut<T: 'static, U>(key: Key<T>, f: &fn(Option<&mut T>) -> U) -> U {
unsafe { local_get_mut(Handle::new(), key, f) }
do get_with(key, MutLoan) |x| {
match x {
None => f(None),
// We're violating a lot of compiler guarantees with this
// invocation of `transmute_mut`, but we're doing runtime checks to
// ensure that it's always valid (only one at a time).
//
// there is no need to be upset!
Some(x) => { f(Some(unsafe { cast::transmute_mut(x) })) }
}
}
}
/**
* Store a value in task-local data. If this key already has a value,
* that value is overwritten (and its destructor is run).
*/
fn get_with<T: 'static, U>(key: Key<T>,
state: LoanState,
f: &fn(Option<&T>) -> U) -> U {
// This function must be extremely careful. Because TLS can store owned
// values, and we must have some form of `get` function other than `pop`,
// this function has to give a `&` reference back to the caller.
//
// One option is to return the reference, but this cannot be sound because
// the actual lifetime of the object is not known. The slot in TLS could not
// be modified until the object goes out of scope, but the TLS code cannot
// know when this happens.
//
// For this reason, the reference is yielded to a specified closure. This
// way the TLS code knows exactly what the lifetime of the yielded pointer
// is, allowing callers to acquire references to owned data. This is also
// sound so long as measures are taken to ensure that while a TLS slot is
// loaned out to a caller, it's not modified recursively.
let map = unsafe { get_local_map() };
let key_value = key_to_key_value(key);
let pos = map.iter().position(|entry| {
match *entry {
Some((k, _, _)) if k == key_value => true, _ => false
}
});
match pos {
None => { return f(None); }
Some(i) => {
let ret;
let mut return_loan = false;
match map[i] {
Some((_, ref data, ref mut loan)) => {
match (state, *loan) {
(_, NoLoan) => {
*loan = state;
return_loan = true;
}
(ImmLoan, ImmLoan) => {}
(want, cur) => {
fail!("TLS slot cannot be borrowed as %s because \
it is already borrowed as %s",
want.describe(), cur.describe());
}
}
// data was created with `~~T as ~LocalData`, so we extract
// pointer part of the trait, (as ~~T), and then use
// compiler coercions to achieve a '&' pointer.
unsafe {
match *cast::transmute::<&TLSValue, &(uint, ~~T)>(data){
(_vtable, ref box) => {
let value: &T = **box;
ret = f(Some(value));
}
}
}
}
_ => abort()
}
// n.b. 'data' and 'loans' are both invalid pointers at the point
// 'f' returned because `f` could have appended more TLS items which
// in turn relocated the vector. Hence we do another lookup here to
// fixup the loans.
if return_loan {
match map[i] {
Some((_, _, ref mut loan)) => { *loan = NoLoan; }
None => abort()
}
}
return ret;
}
}
}
fn abort() -> ! {
#[fixed_stack_segment]; #[inline(never)];
unsafe { libc::abort() }
}
/// Inserts a value into task local storage. If the key is already present in
/// TLS, then the previous value is removed and replaced with the provided data.
///
/// It is considered a runtime error to attempt to set a key which is currently
/// on loan via the `get` or `get_mut` methods.
pub fn set<T: 'static>(key: Key<T>, data: T) {
unsafe { local_set(Handle::new(), key, data) }
let map = unsafe { get_local_map() };
let keyval = key_to_key_value(key);
// When the task-local map is destroyed, all the data needs to be cleaned
// up. For this reason we can't do some clever tricks to store '~T' as a
// '*c_void' or something like that. To solve the problem, we cast
// everything to a trait (LocalData) which is then stored inside the map.
// Upon destruction of the map, all the objects will be destroyed and the
// traits have enough information about them to destroy themselves.
//
// FIXME(#7673): This should be "~data as ~LocalData" (only one sigil)
let data = ~~data as ~LocalData:;
fn insertion_position(map: &mut Map,
key: *libc::c_void) -> Option<uint> {
// First see if the map contains this key already
let curspot = map.iter().position(|entry| {
match *entry {
Some((ekey, _, loan)) if key == ekey => {
if loan != NoLoan {
fail!("TLS value cannot be overwritten because it is
already borrowed as %s", loan.describe())
}
true
}
_ => false,
}
});
// If it doesn't contain the key, just find a slot that's None
match curspot {
Some(i) => Some(i),
None => map.iter().position(|entry| entry.is_none())
}
}
// The type of the local data map must ascribe to Send, so we do the
// transmute here to add the Send bound back on. This doesn't actually
// matter because TLS will always own the data (until its moved out) and
// we're not actually sending it to other schedulers or anything.
let data: ~LocalData = unsafe { cast::transmute(data) };
match insertion_position(map, keyval) {
Some(i) => { map[i] = Some((keyval, data, NoLoan)); }
None => { map.push(Some((keyval, data, NoLoan))); }
}
}
/**
* Modify a task-local data value. If the function returns 'None', the
* data is removed (and its reference dropped).
*/
/// Modifies a task-local value by temporarily removing it from task-local
/// storage and then re-inserting if `Some` is returned from the closure.
///
/// This function will have the same runtime errors as generated from `pop` and
/// `set` (the key must not currently be on loan
pub fn modify<T: 'static>(key: Key<T>, f: &fn(Option<T>) -> Option<T>) {
unsafe {
match f(pop(::cast::unsafe_copy(&key))) {
Some(next) => { set(key, next); }
None => {}
}
match f(pop(key)) {
Some(next) => { set(key, next); }
None => {}
}
}
#[test]
fn test_tls_multitask() {
static my_key: Key<@~str> = &Key;
set(my_key, @~"parent data");
do task::spawn {
// TLS shouldn't carry over.
assert!(get(my_key, |k| k.map_move(|k| *k)).is_none());
set(my_key, @~"child data");
assert!(*(get(my_key, |k| k.map_move(|k| *k)).unwrap()) ==
~"child data");
// should be cleaned up for us
}
// Must work multiple times
assert!(*(get(my_key, |k| k.map_move(|k| *k)).unwrap()) == ~"parent data");
assert!(*(get(my_key, |k| k.map_move(|k| *k)).unwrap()) == ~"parent data");
assert!(*(get(my_key, |k| k.map_move(|k| *k)).unwrap()) == ~"parent data");
}
#[cfg(test)]
mod tests {
use prelude::*;
use super::*;
use task;
#[test]
fn test_tls_overwrite() {
static my_key: Key<@~str> = &Key;
set(my_key, @~"first data");
set(my_key, @~"next data"); // Shouldn't leak.
assert!(*(get(my_key, |k| k.map_move(|k| *k)).unwrap()) == ~"next data");
}
#[test]
fn test_tls_pop() {
static my_key: Key<@~str> = &Key;
set(my_key, @~"weasel");
assert!(*(pop(my_key).unwrap()) == ~"weasel");
// Pop must remove the data from the map.
assert!(pop(my_key).is_none());
}
#[test]
fn test_tls_modify() {
static my_key: Key<@~str> = &Key;
modify(my_key, |data| {
match data {
Some(@ref val) => fail!("unwelcome value: %s", *val),
None => Some(@~"first data")
#[test]
fn test_tls_multitask() {
static my_key: Key<@~str> = &Key;
set(my_key, @~"parent data");
do task::spawn {
// TLS shouldn't carry over.
assert!(get(my_key, |k| k.map_move(|k| *k)).is_none());
set(my_key, @~"child data");
assert!(*(get(my_key, |k| k.map_move(|k| *k)).unwrap()) ==
~"child data");
// should be cleaned up for us
}
});
modify(my_key, |data| {
match data {
Some(@~"first data") => Some(@~"next data"),
Some(@ref val) => fail!("wrong value: %s", *val),
None => fail!("missing value")
}
});
assert!(*(pop(my_key).unwrap()) == ~"next data");
}
#[test]
fn test_tls_crust_automorestack_memorial_bug() {
// This might result in a stack-canary clobber if the runtime fails to
// set sp_limit to 0 when calling the cleanup extern - it might
// automatically jump over to the rust stack, which causes next_c_sp
// to get recorded as something within a rust stack segment. Then a
// subsequent upcall (esp. for logging, think vsnprintf) would run on
// a stack smaller than 1 MB.
static my_key: Key<@~str> = &Key;
do task::spawn {
set(my_key, @~"hax");
// Must work multiple times
assert!(*(get(my_key, |k| k.map_move(|k| *k)).unwrap()) == ~"parent data");
assert!(*(get(my_key, |k| k.map_move(|k| *k)).unwrap()) == ~"parent data");
assert!(*(get(my_key, |k| k.map_move(|k| *k)).unwrap()) == ~"parent data");
}
}
#[test]
fn test_tls_multiple_types() {
static str_key: Key<@~str> = &Key;
static box_key: Key<@@()> = &Key;
static int_key: Key<@int> = &Key;
do task::spawn {
set(str_key, @~"string data");
#[test]
fn test_tls_overwrite() {
static my_key: Key<@~str> = &Key;
set(my_key, @~"first data");
set(my_key, @~"next data"); // Shouldn't leak.
assert!(*(get(my_key, |k| k.map_move(|k| *k)).unwrap()) == ~"next data");
}
#[test]
fn test_tls_pop() {
static my_key: Key<@~str> = &Key;
set(my_key, @~"weasel");
assert!(*(pop(my_key).unwrap()) == ~"weasel");
// Pop must remove the data from the map.
assert!(pop(my_key).is_none());
}
#[test]
fn test_tls_modify() {
static my_key: Key<@~str> = &Key;
modify(my_key, |data| {
match data {
Some(@ref val) => fail!("unwelcome value: %s", *val),
None => Some(@~"first data")
}
});
modify(my_key, |data| {
match data {
Some(@~"first data") => Some(@~"next data"),
Some(@ref val) => fail!("wrong value: %s", *val),
None => fail!("missing value")
}
});
assert!(*(pop(my_key).unwrap()) == ~"next data");
}
#[test]
fn test_tls_crust_automorestack_memorial_bug() {
// This might result in a stack-canary clobber if the runtime fails to
// set sp_limit to 0 when calling the cleanup extern - it might
// automatically jump over to the rust stack, which causes next_c_sp
// to get recorded as something within a rust stack segment. Then a
// subsequent upcall (esp. for logging, think vsnprintf) would run on
// a stack smaller than 1 MB.
static my_key: Key<@~str> = &Key;
do task::spawn {
set(my_key, @~"hax");
}
}
#[test]
fn test_tls_multiple_types() {
static str_key: Key<@~str> = &Key;
static box_key: Key<@@()> = &Key;
static int_key: Key<@int> = &Key;
do task::spawn {
set(str_key, @~"string data");
set(box_key, @@());
set(int_key, @42);
}
}
#[test]
fn test_tls_overwrite_multiple_types() {
static str_key: Key<@~str> = &Key;
static box_key: Key<@@()> = &Key;
static int_key: Key<@int> = &Key;
do task::spawn {
set(str_key, @~"string data");
set(int_key, @42);
// This could cause a segfault if overwriting-destruction is done
// with the crazy polymorphic transmute rather than the provided
// finaliser.
set(int_key, @31337);
}
}
#[test]
#[should_fail]
fn test_tls_cleanup_on_failure() {
static str_key: Key<@~str> = &Key;
static box_key: Key<@@()> = &Key;
static int_key: Key<@int> = &Key;
set(str_key, @~"parent data");
set(box_key, @@());
set(int_key, @42);
}
}
#[test]
fn test_tls_overwrite_multiple_types() {
static str_key: Key<@~str> = &Key;
static box_key: Key<@@()> = &Key;
static int_key: Key<@int> = &Key;
do task::spawn {
set(str_key, @~"string data");
set(int_key, @42);
// This could cause a segfault if overwriting-destruction is done
// with the crazy polymorphic transmute rather than the provided
// finaliser.
do task::spawn {
// spawn_linked
set(str_key, @~"string data");
set(box_key, @@());
set(int_key, @42);
fail!();
}
// Not quite nondeterministic.
set(int_key, @31337);
}
}
#[test]
#[should_fail]
fn test_tls_cleanup_on_failure() {
static str_key: Key<@~str> = &Key;
static box_key: Key<@@()> = &Key;
static int_key: Key<@int> = &Key;
set(str_key, @~"parent data");
set(box_key, @@());
do task::spawn {
// spawn_linked
set(str_key, @~"string data");
set(box_key, @@());
set(int_key, @42);
fail!();
}
// Not quite nondeterministic.
set(int_key, @31337);
fail!();
}
#[test]
fn test_static_pointer() {
static key: Key<@&'static int> = &Key;
static VALUE: int = 0;
let v: @&'static int = @&VALUE;
set(key, v);
}
#[test]
fn test_static_pointer() {
static key: Key<@&'static int> = &Key;
static VALUE: int = 0;
let v: @&'static int = @&VALUE;
set(key, v);
}
#[test]
fn test_owned() {
static key: Key<~int> = &Key;
set(key, ~1);
#[test]
fn test_owned() {
static key: Key<~int> = &Key;
set(key, ~1);
do get(key) |v| {
do get(key) |v| {
do get(key) |v| {
do get(key) |v| {
assert_eq!(**v.unwrap(), 1);
}
assert_eq!(**v.unwrap(), 1);
}
assert_eq!(**v.unwrap(), 1);
}
assert_eq!(**v.unwrap(), 1);
}
set(key, ~2);
do get(key) |v| {
assert_eq!(**v.unwrap(), 2);
}
}
#[test]
fn test_get_mut() {
static key: Key<int> = &Key;
set(key, 1);
do get_mut(key) |v| {
*v.unwrap() = 2;
set(key, ~2);
do get(key) |v| {
assert_eq!(**v.unwrap(), 2);
}
}
do get(key) |v| {
assert_eq!(*v.unwrap(), 2);
#[test]
fn test_get_mut() {
static key: Key<int> = &Key;
set(key, 1);
do get_mut(key) |v| {
*v.unwrap() = 2;
}
do get(key) |v| {
assert_eq!(*v.unwrap(), 2);
}
}
}
#[test]
fn test_same_key_type() {
static key1: Key<int> = &Key;
static key2: Key<int> = &Key;
static key3: Key<int> = &Key;
static key4: Key<int> = &Key;
static key5: Key<int> = &Key;
set(key1, 1);
set(key2, 2);
set(key3, 3);
set(key4, 4);
set(key5, 5);
#[test]
fn test_same_key_type() {
static key1: Key<int> = &Key;
static key2: Key<int> = &Key;
static key3: Key<int> = &Key;
static key4: Key<int> = &Key;
static key5: Key<int> = &Key;
set(key1, 1);
set(key2, 2);
set(key3, 3);
set(key4, 4);
set(key5, 5);
get(key1, |x| assert_eq!(*x.unwrap(), 1));
get(key2, |x| assert_eq!(*x.unwrap(), 2));
get(key3, |x| assert_eq!(*x.unwrap(), 3));
get(key4, |x| assert_eq!(*x.unwrap(), 4));
get(key5, |x| assert_eq!(*x.unwrap(), 5));
}
get(key1, |x| assert_eq!(*x.unwrap(), 1));
get(key2, |x| assert_eq!(*x.unwrap(), 2));
get(key3, |x| assert_eq!(*x.unwrap(), 3));
get(key4, |x| assert_eq!(*x.unwrap(), 4));
get(key5, |x| assert_eq!(*x.unwrap(), 5));
}
#[test]
#[should_fail]
fn test_nested_get_set1() {
static key: Key<int> = &Key;
set(key, 4);
do get(key) |_| {
#[test]
#[should_fail]
fn test_nested_get_set1() {
static key: Key<int> = &Key;
set(key, 4);
do get(key) |_| {
set(key, 4);
}
}
}
#[test]
#[should_fail]
fn test_nested_get_mut2() {
static key: Key<int> = &Key;
set(key, 4);
do get(key) |_| {
get_mut(key, |_| {})
#[test]
#[should_fail]
fn test_nested_get_mut2() {
static key: Key<int> = &Key;
set(key, 4);
do get(key) |_| {
get_mut(key, |_| {})
}
}
}
#[test]
#[should_fail]
fn test_nested_get_mut3() {
static key: Key<int> = &Key;
set(key, 4);
do get_mut(key) |_| {
get(key, |_| {})
#[test]
#[should_fail]
fn test_nested_get_mut3() {
static key: Key<int> = &Key;
set(key, 4);
do get_mut(key) |_| {
get(key, |_| {})
}
}
}
#[test]
#[should_fail]
fn test_nested_get_mut4() {
static key: Key<int> = &Key;
set(key, 4);
do get_mut(key) |_| {
get_mut(key, |_| {})
#[test]
#[should_fail]
fn test_nested_get_mut4() {
static key: Key<int> = &Key;
set(key, 4);
do get_mut(key) |_| {
get_mut(key, |_| {})
}
}
}

4
src/libstd/rt/mod.rs
View File

@ -55,10 +55,6 @@
*/
#[doc(hidden)];
#[deny(unused_imports)];
#[deny(unused_mut)];
#[deny(unused_variable)];
#[deny(unused_unsafe)];
use cell::Cell;
use clone::Clone;

29
src/libstd/rt/task.rs
View File

@ -16,8 +16,8 @@
use borrow;
use cast::transmute;
use cleanup;
use local_data;
use libc::{c_void, uintptr_t};
use ptr;
use prelude::*;
use option::{Option, Some, None};
use rt::borrowck;
@ -80,7 +80,7 @@ pub enum SchedHome {
}
pub struct GarbageCollector;
pub struct LocalStorage(*c_void, Option<extern "Rust" fn(*c_void)>);
pub struct LocalStorage(Option<local_data::Map>);
pub struct Unwinder {
unwinding: bool,
@ -130,7 +130,7 @@ pub fn new_sched_task() -> Task {
Task {
heap: LocalHeap::new(),
gc: GarbageCollector,
storage: LocalStorage(ptr::null(), None),
storage: LocalStorage(None),
logger: StdErrLogger,
unwinder: Unwinder { unwinding: false },
taskgroup: None,
@ -164,7 +164,7 @@ pub fn new_root_homed(stack_pool: &mut StackPool,
Task {
heap: LocalHeap::new(),
gc: GarbageCollector,
storage: LocalStorage(ptr::null(), None),
storage: LocalStorage(None),
logger: StdErrLogger,
unwinder: Unwinder { unwinding: false },
taskgroup: None,
@ -186,7 +186,7 @@ pub fn new_child_homed(&mut self,
Task {
heap: LocalHeap::new(),
gc: GarbageCollector,
storage: LocalStorage(ptr::null(), None),
storage: LocalStorage(None),
logger: StdErrLogger,
unwinder: Unwinder { unwinding: false },
taskgroup: None,
@ -233,15 +233,8 @@ pub fn run(&mut self, f: &fn()) {
// Run the task main function, then do some cleanup.
do f.finally {
// Destroy task-local storage. This may run user dtors.
match self.storage {
LocalStorage(ptr, Some(ref dtor)) => {
(*dtor)(ptr)
}
_ => ()
}
// First, destroy task-local storage. This may run user dtors.
//
// FIXME #8302: Dear diary. I'm so tired and confused.
// There's some interaction in rustc between the box
// annihilator and the TLS dtor by which TLS is
@ -253,7 +246,13 @@ pub fn run(&mut self, f: &fn()) {
// TLS would be reinitialized but never destroyed,
// but somehow this works. I have no idea what's going
// on but this seems to make things magically work. FML.
self.storage = LocalStorage(ptr::null(), None);
//
// (added after initial comment) A possible interaction here is
// that the destructors for the objects in TLS themselves invoke
// TLS, or possibly some destructors for those objects being
// annihilated invoke TLS. Sadly these two operations seemed to
// be intertwined, and miraculously work for now...
self.storage.take();
// Destroy remaining boxes. Also may run user dtors.
unsafe { cleanup::annihilate(); }

322
src/libstd/task/local_data_priv.rs
View File

@ -1,322 +0,0 @@
// Copyright 2012 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.
#[allow(missing_doc)];
use cast;
use libc;
use local_data;
use prelude::*;
use ptr;
use unstable::raw;
use util;
use rt::task::{Task, LocalStorage};
pub enum Handle {
NewHandle(*mut LocalStorage)
}
impl Handle {
pub fn new() -> Handle {
use rt::local::Local;
unsafe {
let task: *mut Task = Local::unsafe_borrow();
NewHandle(&mut (*task).storage)
}
}
}
#[deriving(Eq)]
enum LoanState {
NoLoan, ImmLoan, MutLoan
}
impl LoanState {
fn describe(&self) -> &'static str {
match *self {
NoLoan => "no loan",
ImmLoan => "immutable",
MutLoan => "mutable"
}
}
}
trait LocalData {}
impl<T: 'static> LocalData for T {}
// The task-local-map stores all TLS information for the currently running task.
// It is stored as an owned pointer into the runtime, and it's only allocated
// when TLS is used for the first time. This map must be very carefully
// constructed because it has many mutable loans unsoundly handed out on it to
// the various invocations of TLS requests.
//
// One of the most important operations is loaning a value via `get` to a
// caller. In doing so, the slot that the TLS entry is occupying cannot be
// invalidated because upon returning it's loan state must be updated. Currently
// the TLS map is a vector, but this is possibly dangerous because the vector
// can be reallocated/moved when new values are pushed onto it.
//
// This problem currently isn't solved in a very elegant way. Inside the `get`
// function, it internally "invalidates" all references after the loan is
// finished and looks up into the vector again. In theory this will prevent
// pointers from being moved under our feet so long as LLVM doesn't go too crazy
// with the optimizations.
//
// n.b. Other structures are not sufficient right now:
// * HashMap uses ~[T] internally (push reallocates/moves)
// * TreeMap is plausible, but it's in extra
// * dlist plausible, but not in std
// * a custom owned linked list was attempted, but difficult to write
// and involved a lot of extra code bloat
//
// n.b. Has to be stored with a pointer at outermost layer; the foreign call
// returns void *.
//
// n.b. If TLS is used heavily in future, this could be made more efficient with
// a proper map.
type TaskLocalMap = ~[Option<(*libc::c_void, TLSValue, LoanState)>];
type TLSValue = ~LocalData:;
fn cleanup_task_local_map(map_ptr: *libc::c_void) {
unsafe {
assert!(!map_ptr.is_null());
// Get and keep the single reference that was created at the
// beginning.
let _map: TaskLocalMap = cast::transmute(map_ptr);
// All local_data will be destroyed along with the map.
}
}
// Gets the map from the runtime. Lazily initialises if not done so already.
unsafe fn get_local_map(handle: Handle) -> &mut TaskLocalMap {
unsafe fn newsched_map(local: *mut LocalStorage) -> &mut TaskLocalMap {
// This is based on the same idea as the oldsched code above.
match &mut *local {
// If the at_exit function is already set, then we just need to take
// a loan out on the TLS map stored inside
&LocalStorage(ref mut map_ptr, Some(_)) => {
assert!(map_ptr.is_not_null());
return cast::transmute(map_ptr);
}
// If this is the first time we've accessed TLS, perform similar
// actions to the oldsched way of doing things.
&LocalStorage(ref mut map_ptr, ref mut at_exit) => {
assert!(map_ptr.is_null());
assert!(at_exit.is_none());
let map: TaskLocalMap = ~[];
*map_ptr = cast::transmute(map);
*at_exit = Some(cleanup_task_local_map);
return cast::transmute(map_ptr);
}
}
}
match handle {
NewHandle(local_storage) => newsched_map(local_storage)
}
}
unsafe fn key_to_key_value<T: 'static>(key: local_data::Key<T>) -> *libc::c_void {
let pair: raw::Closure = cast::transmute_copy(&key);
return pair.code as *libc::c_void;
}
pub unsafe fn local_pop<T: 'static>(handle: Handle,
key: local_data::Key<T>) -> Option<T> {
let map = get_local_map(handle);
let key_value = key_to_key_value(key);
for entry in map.mut_iter() {
match *entry {
Some((k, _, loan)) if k == key_value => {
if loan != NoLoan {
fail!("TLS value cannot be removed because it is already \
borrowed as %s", loan.describe());
}
// Move the data out of the `entry` slot via util::replace. This
// is guaranteed to succeed because we already matched on `Some`
// above.
let data = match util::replace(entry, None) {
Some((_, data, _)) => data,
None => abort(),
};
// Move `data` into transmute to get out the memory that it
// owns, we must free it manually later.
let (_vtable, box): (uint, ~~T) = cast::transmute(data);
// Read the box's value (using the compiler's built-in
// auto-deref functionality to obtain a pointer to the base)
let ret = ptr::read_ptr(cast::transmute::<&T, *mut T>(*box));
// Finally free the allocated memory. we don't want this to
// actually touch the memory inside because it's all duplicated
// now, so the box is transmuted to a 0-sized type. We also use
// a type which references `T` because currently the layout
// could depend on whether T contains managed pointers or not.
let _: ~~[T, ..0] = cast::transmute(box);
// Everything is now deallocated, and we own the value that was
// located inside TLS, so we now return it.
return Some(ret);
}
_ => {}
}
}
return None;
}
pub unsafe fn local_get<T: 'static, U>(handle: Handle,
key: local_data::Key<T>,
f: &fn(Option<&T>) -> U) -> U {
local_get_with(handle, key, ImmLoan, f)
}
pub unsafe fn local_get_mut<T: 'static, U>(handle: Handle,
key: local_data::Key<T>,
f: &fn(Option<&mut T>) -> U) -> U {
do local_get_with(handle, key, MutLoan) |x| {
match x {
None => f(None),
// We're violating a lot of compiler guarantees with this
// invocation of `transmute_mut`, but we're doing runtime checks to
// ensure that it's always valid (only one at a time).
//
// there is no need to be upset!
Some(x) => { f(Some(cast::transmute_mut(x))) }
}
}
}
unsafe fn local_get_with<T: 'static, U>(handle: Handle,
key: local_data::Key<T>,
state: LoanState,
f: &fn(Option<&T>) -> U) -> U {
// This function must be extremely careful. Because TLS can store owned
// values, and we must have some form of `get` function other than `pop`,
// this function has to give a `&` reference back to the caller.
//
// One option is to return the reference, but this cannot be sound because
// the actual lifetime of the object is not known. The slot in TLS could not
// be modified until the object goes out of scope, but the TLS code cannot
// know when this happens.
//
// For this reason, the reference is yielded to a specified closure. This
// way the TLS code knows exactly what the lifetime of the yielded pointer
// is, allowing callers to acquire references to owned data. This is also
// sound so long as measures are taken to ensure that while a TLS slot is
// loaned out to a caller, it's not modified recursively.
let map = get_local_map(handle);
let key_value = key_to_key_value(key);
let pos = map.iter().position(|entry| {
match *entry {
Some((k, _, _)) if k == key_value => true, _ => false
}
});
match pos {
None => { return f(None); }
Some(i) => {
let ret;
let mut return_loan = false;
match map[i] {
Some((_, ref data, ref mut loan)) => {
match (state, *loan) {
(_, NoLoan) => {
*loan = state;
return_loan = true;
}
(ImmLoan, ImmLoan) => {}
(want, cur) => {
fail!("TLS slot cannot be borrowed as %s because \
it is already borrowed as %s",
want.describe(), cur.describe());
}
}
// data was created with `~~T as ~LocalData`, so we extract
// pointer part of the trait, (as ~~T), and then use
// compiler coercions to achieve a '&' pointer.
match *cast::transmute::<&TLSValue, &(uint, ~~T)>(data) {
(_vtable, ref box) => {
let value: &T = **box;
ret = f(Some(value));
}
}
}
_ => abort()
}
// n.b. 'data' and 'loans' are both invalid pointers at the point
// 'f' returned because `f` could have appended more TLS items which
// in turn relocated the vector. Hence we do another lookup here to
// fixup the loans.
if return_loan {
match map[i] {
Some((_, _, ref mut loan)) => { *loan = NoLoan; }
None => { abort(); }
}
}
return ret;
}
}
}
fn abort() -> ! {
#[fixed_stack_segment]; #[inline(never)];
unsafe { libc::abort() }
}
pub unsafe fn local_set<T: 'static>(handle: Handle,
key: local_data::Key<T>,
data: T) {
let map = get_local_map(handle);
let keyval = key_to_key_value(key);
// When the task-local map is destroyed, all the data needs to be cleaned
// up. For this reason we can't do some clever tricks to store '~T' as a
// '*c_void' or something like that. To solve the problem, we cast
// everything to a trait (LocalData) which is then stored inside the map.
// Upon destruction of the map, all the objects will be destroyed and the
// traits have enough information about them to destroy themselves.
//
// FIXME(#7673): This should be "~data as ~LocalData" (without the colon at
// the end, and only one sigil)
let data = ~~data as ~LocalData:;
fn insertion_position(map: &mut TaskLocalMap,
key: *libc::c_void) -> Option<uint> {
// First see if the map contains this key already
let curspot = map.iter().position(|entry| {
match *entry {
Some((ekey, _, loan)) if key == ekey => {
if loan != NoLoan {
fail!("TLS value cannot be overwritten because it is
already borrowed as %s", loan.describe())
}
true
}
_ => false,
}
});
// If it doesn't contain the key, just find a slot that's None
match curspot {
Some(i) => Some(i),
None => map.iter().position(|entry| entry.is_none())
}
}
match insertion_position(map, keyval) {
Some(i) => { map[i] = Some((keyval, data, NoLoan)); }
None => { map.push(Some((keyval, data, NoLoan))); }
}
}

1
src/libstd/task/mod.rs
View File

@ -52,7 +52,6 @@
#[cfg(test)] use ptr;
#[cfg(test)] use task;
mod local_data_priv;
pub mod spawn;
/**