diff --git a/src/tools/miri/src/shims/unix/linux/epoll.rs b/src/tools/miri/src/shims/unix/linux/epoll.rs index ff0709dd5ac1..c4bd38c47e54 100644 --- a/src/tools/miri/src/shims/unix/linux/epoll.rs +++ b/src/tools/miri/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; 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>>, + ready_list: Rc, /// A list of thread ids blocked on this epoll instance. thread_id: RefCell>, } @@ -63,7 +64,7 @@ pub struct EpollEventInterest { /// data: u64, /// Ready list of the epoll instance under which this EpollEventInterest is registered. - ready_list: Rc>>, + ready_list: Rc, /// 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>, + clock: RefCell, +} + impl EpollReadyEvents { pub fn new() -> Self { EpollReadyEvents { @@ -127,7 +134,7 @@ impl EpollReadyEvents { } impl Epoll { - fn get_ready_list(&self) -> Rc>> { + fn get_ready_list(&self) -> Rc { Rc::clone(&self.ready_list) } } @@ -207,9 +214,6 @@ 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)) } @@ -377,7 +381,7 @@ 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 @@ -471,8 +475,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> { let epoll_file_description = epfd .downcast::() .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 { @@ -561,9 +564,15 @@ 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::().unwrap().thread_id.borrow_mut().pop() - { + + let epoll = epfd.downcast::().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); }; } @@ -617,7 +626,7 @@ 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); @@ -644,7 +653,11 @@ 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)?; diff --git a/src/tools/miri/tests/pass-dep/libc/libc-epoll-blocking.rs b/src/tools/miri/tests/pass-dep/libc/libc-epoll-blocking.rs index eb38529ae57d..d7675a40163c 100644 --- a/src/tools/miri/tests/pass-dep/libc/libc-epoll-blocking.rs +++ b/src/tools/miri/tests/pass-dep/libc/libc-epoll-blocking.rs @@ -1,5 +1,5 @@ //@only-target: linux -// test_epoll_block_then_unblock depends on a deterministic schedule. +// test_epoll_block_then_unblock and test_epoll_race depend on a deterministic schedule. //@compile-flags: -Zmiri-preemption-rate=0 use std::convert::TryInto; @@ -12,6 +12,7 @@ fn main() { test_epoll_block_without_notification(); test_epoll_block_then_unblock(); test_notification_after_timeout(); + test_epoll_race(); } // Using `as` cast since `EPOLLET` wraps around @@ -137,3 +138,41 @@ fn test_notification_after_timeout() { let expected_value = fds[0] as u64; check_epoll_wait::<1>(epfd, &[(expected_event, expected_value)], 10); } + +// This test shows a data_race before epoll had vector clocks added. +fn test_epoll_race() { + // Create an epoll instance. + let epfd = unsafe { libc::epoll_create1(0) }; + assert_ne!(epfd, -1); + + // Create an eventfd instance. + let flags = libc::EFD_NONBLOCK | libc::EFD_CLOEXEC; + let fd = unsafe { libc::eventfd(0, flags) }; + + // Register eventfd with the epoll instance. + let mut ev = libc::epoll_event { events: EPOLL_IN_OUT_ET, u64: fd as u64 }; + let res = unsafe { libc::epoll_ctl(epfd, libc::EPOLL_CTL_ADD, fd, &mut ev) }; + assert_eq!(res, 0); + + static mut VAL: u8 = 0; + let thread1 = thread::spawn(move || { + // Write to the static mut variable. + unsafe { VAL = 1 }; + // Write to the eventfd instance. + let sized_8_data: [u8; 8] = 1_u64.to_ne_bytes(); + let res = unsafe { libc::write(fd, sized_8_data.as_ptr() as *const libc::c_void, 8) }; + // read returns number of bytes that have been read, which is always 8. + assert_eq!(res, 8); + }); + thread::yield_now(); + // epoll_wait for the event to happen. + let expected_event = u32::try_from(libc::EPOLLIN | libc::EPOLLOUT).unwrap(); + let expected_value = u64::try_from(fd).unwrap(); + check_epoll_wait::<8>(epfd, &[(expected_event, expected_value)], -1); + // Read from the static mut variable. + #[allow(static_mut_refs)] + unsafe { + assert_eq!(VAL, 1) + }; + thread1.join().unwrap(); +}