Add vector clock to epoll

src/shims/unix/linux/epoll.rs

@@ -4,6 +4,7 @@ use std::io;
 use std::rc::{Rc, Weak};
 use std::time::Duration;
 
+use crate::concurrency::{VClock, data_race};
 use crate::shims::unix::fd::{FdId, FileDescriptionRef, WeakFileDescriptionRef};
 use crate::shims::unix::*;
 use crate::*;
@@ -19,7 +20,7 @@ struct Epoll {
     /// and file descriptor value.
     // This is an Rc because EpollInterest need to hold a reference to update
     // it.
-    ready_list: Rc<RefCell<BTreeMap<(FdId, i32), EpollEventInstance>>>,
+    ready_list: Rc<ReadyList>,
     /// A list of thread ids blocked on this epoll instance.
     thread_id: RefCell<Vec<ThreadId>>,
 }
@@ -63,7 +64,7 @@ pub struct EpollEventInterest {
     /// <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<RefCell<BTreeMap<(FdId, i32), EpollEventInstance>>>,
+    ready_list: Rc<ReadyList>,
     /// The epoll file description that this EpollEventInterest is registered under.
     weak_epfd: WeakFileDescriptionRef,
 }
@@ -88,6 +89,12 @@ pub struct EpollReadyEvents {
     pub epollerr: bool,
 }
 
+#[derive(Debug, Default)]
+struct ReadyList {
+    mapping: RefCell<BTreeMap<(FdId, i32), EpollEventInstance>>,
+    clock: RefCell<VClock>,
+}
+
 impl EpollReadyEvents {
     pub fn new() -> Self {
         EpollReadyEvents {
@@ -127,7 +134,7 @@ impl EpollReadyEvents {
 }
 
 impl Epoll {
-    fn get_ready_list(&self) -> Rc<RefCell<BTreeMap<(FdId, i32), EpollEventInstance>>> {
+    fn get_ready_list(&self) -> Rc<ReadyList> {
         Rc::clone(&self.ready_list)
     }
 }
@@ -186,7 +193,9 @@ impl EpollInterestTable {
 }
 
 impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
-pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
+pub trait EvalContextExt<'tcx>:
+    crate::MiriInterpCxExt<'tcx> + data_race::EvalContextExt<'tcx>
+{
     /// This function returns a file descriptor referring to the new `Epoll` instance. This file
     /// descriptor is used for all subsequent calls to the epoll interface. If the `flags` argument
     /// is 0, then this function is the same as `epoll_create()`.
@@ -207,9 +216,6 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             );
         }
 
-        let mut epoll_instance = Epoll::default();
-        epoll_instance.ready_list = Rc::new(RefCell::new(BTreeMap::new()));
-
         let fd = this.machine.fds.insert_new(Epoll::default());
         Ok(Scalar::from_i32(fd))
     }
@@ -378,7 +384,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             drop(epoll_interest);
 
             // Remove related epoll_interest from ready list.
-            ready_list.borrow_mut().remove(&epoll_key);
+            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
@@ -473,8 +479,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             let epoll_file_description = epfd
                 .downcast::<Epoll>()
                 .ok_or_else(|| err_unsup_format!("non-epoll FD passed to `epoll_wait`"))?;
-            let binding = epoll_file_description.get_ready_list();
-            ready_list_empty = binding.borrow_mut().is_empty();
+            ready_list_empty = epoll_file_description.ready_list.mapping.borrow().is_empty();
             thread_ids = epoll_file_description.thread_id.borrow_mut();
         }
         if timeout == 0 || !ready_list_empty {
@@ -563,9 +568,15 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                         // holds a strong ref to epoll_interest.
                         let epfd = epoll_interest.borrow().weak_epfd.upgrade().unwrap();
                         // FIXME: We can randomly pick a thread to unblock.
-                        if let Some(thread_id) =
-                            epfd.downcast::<Epoll>().unwrap().thread_id.borrow_mut().pop()
-                        {
+
+                        let epoll = epfd.downcast::<Epoll>().unwrap();
+
+                        // Synchronize running thread to the epoll ready list.
+                        if let Some(clock) = &this.release_clock() {
+                            epoll.ready_list.clock.borrow_mut().join(clock);
+                        }
+
+                        if let Some(thread_id) = epoll.thread_id.borrow_mut().pop() {
                             waiter.push(thread_id);
                         };
                     }
@@ -619,7 +630,7 @@ 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.borrow_mut();
+        let ready_list = &mut epoll_event_interest.ready_list.mapping.borrow_mut();
         let event_instance = EpollEventInstance::new(flags, epoll_event_interest.data);
         // Triggers the notification by inserting it to the ready list.
         ready_list.insert(epoll_key, event_instance);
@@ -646,7 +657,11 @@ fn blocking_epoll_callback<'tcx>(
         .ok_or_else(|| err_unsup_format!("non-epoll FD passed to `epoll_wait`"))?;
 
     let ready_list = epoll_file_description.get_ready_list();
-    let mut ready_list = ready_list.borrow_mut();
+
+    // Synchronize waking thread from the epoll ready list.
+    ecx.acquire_clock(&ready_list.clock.borrow());
+
+    let mut ready_list = ready_list.mapping.borrow_mut();
     let mut num_of_events: i32 = 0;
     let mut array_iter = ecx.project_array_fields(events)?;