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Fix the dequeuing order of items in a FutexBucket

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He Sun 2020-08-11 20:30:09 +08:00 committed by Tate, Hongliang Tian
parent 6d39587c40
commit b04aa2d7ea
1 changed files with 26 additions and 21 deletions
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47
src/libos/src/process/do_futex.rs
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@ -75,7 +75,7 @@ pub fn futex_wait(
futex_val: i32, futex_val: i32,
timeout: &Option<timespec_t>, timeout: &Option<timespec_t>,
) -> Result<()> { ) -> Result<()> {
info!( debug!(
"futex_wait addr: {:#x}, val: {}, timeout: {:?}", "futex_wait addr: {:#x}, val: {}, timeout: {:?}",
futex_addr as usize, futex_val, timeout futex_addr as usize, futex_val, timeout
); );
@ -130,6 +130,11 @@ pub fn futex_wait(
/// Do futex wake /// Do futex wake
pub fn futex_wake(futex_addr: *const i32, max_count: usize) -> Result<usize> { pub fn futex_wake(futex_addr: *const i32, max_count: usize) -> Result<usize> {
debug!(
"futex_wake addr: {:#x}, max_count: {}",
futex_addr as usize, max_count
);
// Get and lock the futex bucket // Get and lock the futex bucket
let futex_key = FutexKey::new(futex_addr); let futex_key = FutexKey::new(futex_addr);
let (_, futex_bucket_ref) = FUTEX_BUCKETS.get_bucket(futex_key); let (_, futex_bucket_ref) = FUTEX_BUCKETS.get_bucket(futex_key);
@ -266,29 +271,29 @@ impl FutexBucket {
self.queue.push_back(item); self.queue.push_back(item);
} }
// TODO: this is an O(N) operation. Try to make it more efficient
pub fn dequeue_item(&mut self, futex_item: &FutexItem) -> Option<FutexItem> { pub fn dequeue_item(&mut self, futex_item: &FutexItem) -> Option<FutexItem> {
let item_i = self.queue.iter().position(|item| *item == *futex_item); let item_i = self.queue.iter().position(|item| *item == *futex_item);
if item_i.is_none() { if item_i.is_none() {
return None; return None;
} }
self.queue.swap_remove_back(item_i.unwrap()) self.queue.remove(item_i.unwrap())
} }
// TODO: consider using std::future to improve the readability // TODO: consider using std::future to improve the readability
pub fn dequeue_and_wake_items(&mut self, key: FutexKey, max_count: usize) -> usize { pub fn dequeue_and_wake_items(&mut self, key: FutexKey, max_count: usize) -> usize {
let mut count = 0; let mut count = 0;
let mut idx = 0;
let mut items_to_wake = Vec::new(); let mut items_to_wake = Vec::new();
while count < max_count && idx < self.queue.len() {
if key == self.queue[idx].key { self.queue.retain(|item| {
if let Some(item) = self.queue.swap_remove_back(idx) { if count >= max_count || key != item.key {
items_to_wake.push(item); true
count += 1;
}
} else { } else {
idx += 1; items_to_wake.push(item.clone());
} count += 1;
false
} }
});
FutexItem::batch_wake(&items_to_wake); FutexItem::batch_wake(&items_to_wake);
count count
@ -315,18 +320,18 @@ impl FutexBucket {
max_nrequeues: usize, max_nrequeues: usize,
) -> () { ) -> () {
let mut count = 0; let mut count = 0;
let mut idx = 0;
while count < max_nrequeues && idx < self.queue.len() { self.queue.retain(|item| {
if key == self.queue[idx].key { if count >= max_nrequeues || key != item.key {
if let Some(mut item) = self.queue.swap_remove_back(idx) { true
item.key = new_key;
another.enqueue_item(item);
count += 1;
}
} else { } else {
idx += 1; let mut new_item = item.clone();
} new_item.key = new_key;
another.enqueue_item(new_item);
count += 1;
false
} }
});
} }
} }