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Adjust and correct parts of the futex implementation code

This commit is contained in:
Chen Chengjun 2025-06-16 02:02:22 +00:00 committed by Tate, Hongliang Tian
parent 45059bad21
commit 860bb6c07f
2 changed files with 17 additions and 22 deletions
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1
kernel/src/process/posix_thread/futex.rs
View File

@ -113,7 +113,6 @@ pub fn futex_wake_bitset(
let (_, futex_bucket_ref) = get_futex_bucket(futex_key);
let mut futex_bucket = futex_bucket_ref.lock();
let res = futex_bucket.remove_and_wake_items(futex_key, max_count);
drop(futex_bucket);
Ok(res)
}

38
kernel/src/syscall/futex.rs
View File

@ -21,10 +21,10 @@ use crate::{
pub fn sys_futex(
futex_addr: Vaddr,
futex_op: i32,
futex_val: u64,
futex_val: u32,
utime_addr: Vaddr,
futex_new_addr: u64,
bitset: u64,
futex_new_addr: Vaddr,
bitset: u32,
ctx: &Context,
) -> Result<SyscallReturn> {
let (futex_op, futex_flags) = futex_op_and_flags_from_u32(futex_op as _)?;
@ -33,13 +33,6 @@ pub fn sys_futex(
futex_op, futex_flags, futex_addr, futex_val
);
let get_futex_val = |val: i32| -> Result<usize> {
if val < 0 {
return_errno_with_message!(Errno::EINVAL, "the futex val must not be negative");
}
Ok(val as usize)
};
let get_futex_timeout = |timeout_addr: Vaddr| -> Result<Option<ManagedTimeout<'static>>> {
if timeout_addr == 0 {
return Ok(None);
@ -107,21 +100,18 @@ pub fn sys_futex(
.map(|_| 0)
}
FutexOp::FUTEX_WAKE => {
// From gVisor/test/syscalls/linux/futex.cc:260: "The Linux kernel wakes one waiter even if val is 0 or negative."
// To be consistent with Linux, we set the max_count to 1 if it is 0 or negative.
let max_count = (futex_val as i32).max(1) as usize;
futex_wake(futex_addr as _, max_count, pid).map(|count| count as isize)
let max_count = futex_val_to_max_count(futex_val);
futex_wake(futex_addr as _, max_count, pid)
}
FutexOp::FUTEX_WAKE_BITSET => {
// From gVisor/test/syscalls/linux/futex.cc:260: "The Linux kernel wakes one waiter even if val is 0 or negative."
// To be consistent with Linux, we set the max_count to 1 if it is 0 or negative.
let max_count = (futex_val as i32).max(1) as usize;
let max_count = futex_val_to_max_count(futex_val);
futex_wake_bitset(futex_addr as _, max_count, bitset as _, pid)
.map(|count| count as isize)
}
FutexOp::FUTEX_REQUEUE => {
let max_nwakes = get_futex_val(futex_val as i32)?;
let max_nrequeues = get_futex_val(utime_addr as i32)?;
let max_nwakes = futex_val_to_max_count(futex_val);
// The `utime_addr` is used as the maximum number of requeues in this case.
// When `utime_addr` is 0 or negative, it means no requeues.
let max_nrequeues = (utime_addr as i32).max(0) as usize;
futex_requeue(
futex_addr as _,
max_nwakes,
@ -129,7 +119,6 @@ pub fn sys_futex(
futex_new_addr as _,
pid,
)
.map(|nwakes| nwakes as _)
}
_ => {
warn!("futex op = {:?}", futex_op);
@ -145,3 +134,10 @@ pub fn sys_futex(
debug!("futex returns, tid= {} ", ctx.posix_thread.tid());
Ok(SyscallReturn::Return(res as _))
}
fn futex_val_to_max_count(futex_val: u32) -> usize {
// From gVisor/test/syscalls/linux/futex.cc:260: "The Linux kernel wakes one
// waiter even if val is 0 or negative." To be consistent with Linux, we set
// the max_count to 1 if it is 0 or negative.
(futex_val as i32).max(1) as usize
}