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comment and test regarding notifications on writes that dont change readiness
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@ -35,6 +35,7 @@ impl EpollEventInstance {
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EpollEventInstance { events, data }
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}
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}
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/// EpollEventInterest registers the file description information to an epoll
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/// instance during a successful `epoll_ctl` call. It also stores additional
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/// information needed to check and update readiness state for `epoll_wait`.
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@ -434,7 +435,9 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
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/// For a specific file description, get its ready events and update
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/// the corresponding ready list. This function is called whenever a file description
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/// is registered with epoll, or when its readiness *might* have changed.
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/// is registered with epoll, or the buffer it reads from / writes to changed.
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/// This *will* report an event if anyone is subscribed to it, without any further
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/// filtering, so do not call this function when an FD didn't have anything happen to it!
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fn check_and_update_readiness(&self, fd_ref: &FileDescriptionRef) -> InterpResult<'tcx, ()> {
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let this = self.eval_context_ref();
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let id = fd_ref.get_id();
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@ -200,6 +200,7 @@ impl FileDescription for SocketPair {
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drop(writebuf);
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// Notification should be provided for peer fd as it became readable.
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// The kernel does this even if the fd was already readable before, so we follow suit.
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ecx.check_and_update_readiness(&peer_fd)?;
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return Ok(Ok(actual_write_size));
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@ -83,6 +83,18 @@ fn test_epoll_socketpair() {
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let expected_value = u64::try_from(fds[1]).unwrap();
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assert!(check_epoll_wait::<8>(epfd, vec![(expected_event, expected_value)]));
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// Check that this is indeed using "ET" (edge-trigger) semantics: a second epoll should return nothing.
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assert!(check_epoll_wait::<8>(epfd, vec![]));
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// Write some more to fd[0].
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let data = "abcde".as_bytes().as_ptr();
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let res = unsafe { libc::write(fds[0], data as *const libc::c_void, 5) };
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assert_eq!(res, 5);
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// This did not change the readiness of fd[1]. And yet, we're seeing the event reported
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// again by the kernel, so Miri does the same.
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assert!(check_epoll_wait::<8>(epfd, vec![(expected_event, expected_value)]));
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// Close the peer socketpair.
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let res = unsafe { libc::close(fds[0]) };
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assert_eq!(res, 0);
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