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Merge pull request #4115 from RalfJung/epoll

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epoll: avoid some clones
This commit is contained in:
Oli Scherer 2024-12-29 09:04:36 +00:00 • committed by GitHub
commit cabc386bd1
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2 changed files with 40 additions and 41 deletions
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8
src/tools/miri/src/shims/files.rs
View file

@ -50,9 +50,15 @@ impl<T: ?Sized> FileDescriptionRef<T> {
}
/// Holds a weak reference to the actual file description.
#[derive(Clone, Debug)]
#[derive(Debug)]
pub struct WeakFileDescriptionRef<T: ?Sized>(Weak<FdIdWith<T>>);
impl<T: ?Sized> Clone for WeakFileDescriptionRef<T> {
fn clone(&self) -> Self {
WeakFileDescriptionRef(self.0.clone())
}
}
impl<T: ?Sized> FileDescriptionRef<T> {
pub fn downgrade(this: &Self) -> WeakFileDescriptionRef<T> {
WeakFileDescriptionRef(Rc::downgrade(&this.0))

73
src/tools/miri/src/shims/unix/linux_like/epoll.rs
View file

@ -12,7 +12,7 @@ use crate::shims::unix::UnixFileDescription;
use crate::*;
/// An `Epoll` file descriptor connects file handles and epoll events
#[derive(Clone, Debug, Default)]
#[derive(Debug, Default)]
struct Epoll {
/// A map of EpollEventInterests registered under this epoll instance.
/// Each entry is differentiated using FdId and file descriptor value.
@ -20,9 +20,7 @@ struct Epoll {
/// A map of EpollEventInstance that will be returned when `epoll_wait` is called.
/// Similar to interest_list, the entry is also differentiated using FdId
/// and file descriptor value.
// This is an Rc because EpollInterest need to hold a reference to update
// it.
ready_list: Rc<ReadyList>,
ready_list: ReadyList,
/// A list of thread ids blocked on this epoll instance.
blocked_tid: RefCell<Vec<ThreadId>>,
}
@ -59,7 +57,7 @@ impl EpollEventInstance {
/// see the man page:
///
/// <https://man7.org/linux/man-pages/man2/epoll_ctl.2.html>
#[derive(Clone, Debug)]
#[derive(Debug)]
pub struct EpollEventInterest {
/// The file descriptor value of the file description registered.
/// This is only used for ready_list, to inform userspace which FD triggered an event.
@ -73,9 +71,9 @@ pub struct EpollEventInterest {
/// but only u64 is supported for now.
/// <https://man7.org/linux/man-pages/man3/epoll_event.3type.html>
data: u64,
/// Ready list of the epoll instance under which this EpollEventInterest is registered.
ready_list: Rc<ReadyList>,
/// The epoll file description that this EpollEventInterest is registered under.
/// This is weak to avoid cycles, but an upgrade is always guaranteed to succeed
/// because only the `Epoll` holds a strong ref to a `EpollEventInterest`.
weak_epfd: WeakFileDescriptionRef<Epoll>,
}
@ -142,12 +140,6 @@ impl EpollReadyEvents {
}
}
impl Epoll {
fn get_ready_list(&self) -> Rc<ReadyList> {
Rc::clone(&self.ready_list)
}
}
impl FileDescription for Epoll {
fn name(&self) -> &'static str {
"epoll"
@ -279,12 +271,11 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
let Some(epfd) = this.machine.fds.get(epfd_value) else {
return this.set_last_error_and_return_i32(LibcError("EBADF"));
};
let epoll_file_description = epfd
let epfd = epfd
.downcast::<Epoll>()
.ok_or_else(|| err_unsup_format!("non-epoll FD passed to `epoll_ctl`"))?;
let mut interest_list = epoll_file_description.interest_list.borrow_mut();
let ready_list = &epoll_file_description.ready_list;
let mut interest_list = epfd.interest_list.borrow_mut();
let Some(fd_ref) = this.machine.fds.get(fd) else {
return this.set_last_error_and_return_i32(LibcError("EBADF"));
@ -345,30 +336,33 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
}
}
// Create an epoll_interest.
let interest = Rc::new(RefCell::new(EpollEventInterest {
fd_num: fd,
events,
data,
ready_list: Rc::clone(ready_list),
weak_epfd: FileDescriptionRef::downgrade(&epoll_file_description),
}));
if op == epoll_ctl_add {
// Create an epoll_interest.
let interest = Rc::new(RefCell::new(EpollEventInterest {
fd_num: fd,
events,
data,
weak_epfd: FileDescriptionRef::downgrade(&epfd),
}));
// Notification will be returned for current epfd if there is event in the file
// descriptor we registered.
check_and_update_one_event_interest(&fd_ref, &interest, id, this)?;
// Insert an epoll_interest to global epoll_interest list.
this.machine.epoll_interests.insert_epoll_interest(id, Rc::downgrade(&interest));
interest_list.insert(epoll_key, Rc::clone(&interest));
interest_list.insert(epoll_key, interest);
} else {
// Directly modify the epoll_interest so the global epoll_event_interest table
// will be updated too.
let mut epoll_interest = interest_list.get_mut(&epoll_key).unwrap().borrow_mut();
epoll_interest.events = events;
epoll_interest.data = data;
// Modify the existing interest.
let epoll_interest = interest_list.get_mut(&epoll_key).unwrap();
{
let mut epoll_interest = epoll_interest.borrow_mut();
epoll_interest.events = events;
epoll_interest.data = data;
}
// Updating an FD interest triggers events.
check_and_update_one_event_interest(&fd_ref, epoll_interest, id, this)?;
}
// Notification will be returned for current epfd if there is event in the file
// descriptor we registered.
check_and_update_one_event_interest(&fd_ref, &interest, id, this)?;
interp_ok(Scalar::from_i32(0))
} else if op == epoll_ctl_del {
let epoll_key = (id, fd);
@ -381,7 +375,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
drop(epoll_interest);
// Remove related epoll_interest from ready list.
ready_list.mapping.borrow_mut().remove(&epoll_key);
epfd.ready_list.mapping.borrow_mut().remove(&epoll_key);
// Remove dangling EpollEventInterest from its global table.
// .unwrap() below should succeed because the file description id must have registered
@ -587,13 +581,14 @@ fn ready_list_next(
/// notification to only one epoll instance.
fn check_and_update_one_event_interest<'tcx>(
fd_ref: &DynFileDescriptionRef,
interest: &Rc<RefCell<EpollEventInterest>>,
interest: &RefCell<EpollEventInterest>,
id: FdId,
ecx: &MiriInterpCx<'tcx>,
) -> InterpResult<'tcx, bool> {
// Get the bitmask of ready events for a file description.
let ready_events_bitmask = fd_ref.as_unix().get_epoll_ready_events()?.get_event_bitmask(ecx);
let epoll_event_interest = interest.borrow();
let epfd = epoll_event_interest.weak_epfd.upgrade().unwrap();
// This checks if any of the events specified in epoll_event_interest.events
// match those in ready_events.
let flags = epoll_event_interest.events & ready_events_bitmask;
@ -601,7 +596,7 @@ fn check_and_update_one_event_interest<'tcx>(
// insert an epoll_return to the ready list.
if flags != 0 {
let epoll_key = (id, epoll_event_interest.fd_num);
let ready_list = &mut epoll_event_interest.ready_list.mapping.borrow_mut();
let mut ready_list = epfd.ready_list.mapping.borrow_mut();
let mut event_instance = EpollEventInstance::new(flags, epoll_event_interest.data);
// If we are tracking data races, remember the current clock so we can sync with it later.
ecx.release_clock(|clock| {
@ -623,9 +618,7 @@ fn return_ready_list<'tcx>(
events: &MPlaceTy<'tcx>,
ecx: &mut MiriInterpCx<'tcx>,
) -> InterpResult<'tcx> {
let ready_list = epfd.get_ready_list();
let mut ready_list = ready_list.mapping.borrow_mut();
let mut ready_list = epfd.ready_list.mapping.borrow_mut();
let mut num_of_events: i32 = 0;
let mut array_iter = ecx.project_array_fields(events)?;