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make F64Table concurency safe

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This commit is contained in:
Bennet Bleßmann
2023-09-02 22:27:43 +02:00
parent c7ec5a13a5
commit 5928d64d7a
3 changed files with 114 additions and 63 deletions
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165
src/arena.rs
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@@ -4,12 +4,16 @@ use crate::machine::loader::LiveLoadState;
use crate::machine::machine_indices::*;
use crate::machine::streams::*;
use crate::raw_block::*;
use crate::rcu::Rcu;
use crate::rcu::RcuRef;
use crate::read::*;
use crate::parser::dashu::{Integer, Rational};
use ordered_float::OrderedFloat;
use tokio::sync::RwLock;
use std::alloc;
use std::cell::UnsafeCell;
use std::fmt;
use std::hash::{Hash, Hasher};
use std::mem;
@@ -34,25 +38,35 @@ macro_rules! float_alloc {
let result = $e;
#[allow(unused_unsafe)]
unsafe {
$arena.f64_tbl.build_with(result)
$arena.f64_tbl.build_with(result).as_ptr()
}
}};
}
#[cfg(test)]
use std::cell::RefCell;
use std::sync::Arc;
use std::sync::Mutex;
use std::sync::Weak;
const F64_TABLE_INIT_SIZE: usize = 1 << 16;
const F64_TABLE_ALIGN: usize = 8;
#[cfg(test)]
thread_local! {
static F64_TABLE_BUF_BASE: RefCell<*const u8> = RefCell::new(ptr::null_mut());
#[inline(always)]
fn global_f64table() -> &'static RwLock<Weak<F64Table>> {
#[cfg(feature = "rust_beta_channel")]
{
// const Weak::new will be stabilized in 1.73 which is currently in beta,
// till then we need a OnceLock for initialization
static GLOBAL_ATOM_TABLE: RwLock<Weak<F64Table>> = RwLock::const_new(Weak::new());
&GLOBAL_ATOM_TABLE
}
#[cfg(not(feature = "rust_beta_channel"))]
{
use std::sync::OnceLock;
static GLOBAL_ATOM_TABLE: OnceLock<RwLock<Weak<F64Table>>> = OnceLock::new();
GLOBAL_ATOM_TABLE.get_or_init(|| RwLock::new(Weak::new()))
}
}
#[cfg(not(test))]
static mut F64_TABLE_BUF_BASE: *const u8 = ptr::null_mut();
impl RawBlockTraits for F64Table {
#[inline]
fn init_size() -> usize {
@@ -67,65 +81,86 @@ impl RawBlockTraits for F64Table {
#[derive(Debug)]
pub struct F64Table {
block: RawBlock<F64Table>,
}
#[cfg(test)]
fn set_f64_tbl_buf_base(ptr: *const u8) {
F64_TABLE_BUF_BASE.with(|f64_table_buf_base| {
*f64_table_buf_base.borrow_mut() = ptr;
});
}
#[cfg(test)]
pub(crate) fn get_f64_tbl_buf_base() -> *const u8 {
F64_TABLE_BUF_BASE.with(|f64_table_buf_base| *f64_table_buf_base.borrow())
}
#[cfg(not(test))]
fn set_f64_tbl_buf_base(ptr: *const u8) {
unsafe {
F64_TABLE_BUF_BASE = ptr;
}
}
#[cfg(not(test))]
pub(crate) fn get_f64_tbl_buf_base() -> *const u8 {
unsafe { F64_TABLE_BUF_BASE }
block: Rcu<RawBlock<F64Table>>,
update: Mutex<()>,
}
#[inline(always)]
pub fn lookup_float(offset: usize) -> *mut OrderedFloat<f64> {
let base = get_f64_tbl_buf_base() as usize;
(base + offset) as *mut _
pub fn lookup_float(
offset: F64Offset,
) -> RcuRef<RawBlock<F64Table>, UnsafeCell<OrderedFloat<f64>>> {
let f64table = global_f64table()
.blocking_read()
.upgrade()
.expect("We should only be looking up floats while there is a float table");
RcuRef::try_map(f64table.block.active_epoch(), |raw_block| unsafe {
raw_block
.base
.offset(offset.0 as isize)
.cast_mut()
.cast::<UnsafeCell<OrderedFloat<f64>>>()
.as_ref()
})
.expect("The offset should result in a non-null pointer")
}
impl F64Table {
#[inline]
pub fn new() -> Self {
let table = Self {
block: RawBlock::new(),
};
set_f64_tbl_buf_base(table.block.base);
table
pub fn new() -> Arc<Self> {
let upgraded = global_f64table().blocking_read().upgrade();
// don't inline upgraded, otherwise temporary will be dropped too late in case of None
if let Some(atom_table) = upgraded {
atom_table
} else {
let mut guard = global_f64table().blocking_write();
// try to upgrade again in case we lost the race on the write lock
if let Some(atom_table) = guard.upgrade() {
atom_table
} else {
let atom_table = Arc::new(Self {
block: Rcu::new(RawBlock::new()),
update: Mutex::new(()),
});
*guard = Arc::downgrade(&atom_table);
atom_table
}
}
}
pub unsafe fn build_with(&mut self, value: f64) -> F64Ptr {
pub unsafe fn build_with(&self, value: f64) -> F64Offset {
let update_guard = self.update.lock();
// we don't have an index table for lookups as AtomTable does so
// just get the epoch after we take the upgrade lock
let mut block_epoch = self.block.active_epoch();
let mut ptr;
loop {
ptr = self.block.alloc(mem::size_of::<f64>());
ptr = block_epoch.alloc(mem::size_of::<f64>());
if ptr.is_null() {
self.block.grow();
set_f64_tbl_buf_base(self.block.base);
let new_block = block_epoch.grow_new().unwrap();
self.block.replace(new_block);
block_epoch = self.block.active_epoch();
} else {
break;
}
}
ptr::write(ptr as *mut OrderedFloat<f64>, OrderedFloat(value));
F64Ptr(ptr::NonNull::new_unchecked(ptr as *mut _))
let float = F64Offset {
0: ptr as usize - block_epoch.base as usize,
};
// atometable would have to update the index table at this point
// expicit drop to ensure we don't accidentally drop it early
drop(update_guard);
float
}
}
@@ -336,12 +371,18 @@ pub trait ArenaAllocated: Sized {
}
}
#[derive(Copy, Clone, Debug)]
pub struct F64Ptr(pub ptr::NonNull<OrderedFloat<f64>>);
#[derive(Debug)]
pub struct F64Ptr(RcuRef<RawBlock<F64Table>, UnsafeCell<OrderedFloat<f64>>>);
impl Clone for F64Ptr {
fn clone(&self) -> Self {
Self(RcuRef::clone(&self.0))
}
}
impl PartialEq for F64Ptr {
fn eq(&self, other: &F64Ptr) -> bool {
self.0 == other.0 || &**self == &**other
RcuRef::ptr_eq(&self.0, &other.0) || self.deref() == other.deref()
}
}
@@ -377,26 +418,26 @@ impl Deref for F64Ptr {
#[inline]
fn deref(&self) -> &Self::Target {
unsafe { &*self.0.as_ptr() }
unsafe { &*self.0.get().as_ref().unwrap() }
}
}
impl DerefMut for F64Ptr {
#[inline]
fn deref_mut(&mut self) -> &mut Self::Target {
unsafe { &mut *self.0.as_ptr() }
unsafe { &mut *self.0.get().as_mut().unwrap() }
}
}
impl F64Ptr {
#[inline(always)]
pub fn from_offset(offset: usize) -> Self {
unsafe { F64Ptr(ptr::NonNull::new_unchecked(lookup_float(offset))) }
pub fn from_offset(offset: F64Offset) -> Self {
Self(lookup_float(offset))
}
#[inline(always)]
pub fn as_offset(&self) -> F64Offset {
F64Offset(self.0.as_ptr() as usize - get_f64_tbl_buf_base() as usize)
F64Offset(self.0.get() as usize - RcuRef::get_root(&self.0).base as usize)
}
}
@@ -416,7 +457,7 @@ impl F64Offset {
#[inline(always)]
pub fn as_ptr(self) -> F64Ptr {
F64Ptr::from_offset(self.0)
F64Ptr::from_offset(self)
}
#[inline(always)]
@@ -672,7 +713,7 @@ struct AllocSlab {
#[derive(Debug)]
pub struct Arena {
base: *mut AllocSlab,
pub f64_tbl: F64Table,
pub f64_tbl: Arc<F64Table>,
}
unsafe impl Send for Arena {}
@@ -804,6 +845,8 @@ const_assert!(mem::size_of::<OrderedFloat<f64>>() == 8);
#[cfg(test)]
mod tests {
use std::ops::Deref;
use crate::machine::mock_wam::*;
use crate::machine::partial_string::*;
@@ -812,15 +855,15 @@ mod tests {
#[test]
fn float_ptr_cast() {
let mut wam = MockWAM::new();
let wam = MockWAM::new();
let f = 0f64;
let fp = float_alloc!(f, wam.machine_st.arena);
let mut cell = HeapCellValue::from(fp);
let mut cell = HeapCellValue::from(fp.clone());
assert_eq!(cell.get_tag(), HeapCellValueTag::F64);
assert_eq!(cell.get_mark_bit(), false);
assert_eq!(*fp, OrderedFloat(f));
assert_eq!(fp.deref(), &OrderedFloat(f));
cell.set_mark_bit(true);