Struct SyncFence 

pub struct SyncFence { /* private fields */ }

A kernel sync_file fence.

Default-constructs empty, as the C++ does. Here a commit’s OUT_FENCE_PTR comes back as an OwnedFd, which SyncFence::from_owned adopts.

Implementations

impl SyncFence

pub const fn new() -> Self

An empty fence holding no descriptor.

pub fn import(fd: BorrowedFd<'_>) -> Result<Self, SyncError>

Import a fence by duplicating fd.

The caller keeps ownership of fd and may close it immediately; this fence owns the duplicate. Matches the C++ import_fd, which dups for the same reason.

Errors

SyncError::Io if dup fails — in practice EMFILE.

pub const fn from_owned(fd: OwnedFd) -> Self

Take ownership of an existing descriptor without duplicating it.

The natural constructor when a commit has just produced an OUT_FENCE_PTR descriptor that nothing else holds. The C++ has no equivalent: it cannot express “this fd is yours now” in a type, so it dups unconditionally and the caller closes its copy.

pub const fn is_valid(&self) -> bool

Whether this holds a real sync_file descriptor.

pub fn as_fd(&self) -> Option<BorrowedFd<'_>>

The underlying descriptor, for a plane’s IN_FENCE_FD property.

Borrowed, never transferred: the kernel does not close IN_FENCE_FD, so this fence still closes it on drop.

pub fn into_owned_fd(self) -> Option<OwnedFd>

Release the descriptor to the caller, consuming the fence; None if it held none.

pub fn wait(&self, timeout: Duration) -> Result<(), SyncError>

Wait for the fence to signal, up to timeout.

Interruption

A signal landing mid-wait surfaces as SyncError::Io(Errno::INTR), matching the C++, which returns EINTR to its caller. This is deliberately not the PageFlip::dispatch contract (invariant 3), which retries internally: a fence wait is a caller-owned wait, and swallowing EINTR here would make the timeout unobservable to a caller that wants to act on the signal.

Errors

• SyncError::Empty if the fence holds no descriptor.
• SyncError::TimedOut if timeout elapsed first.
• SyncError::Io if poll failed.

pub fn merge(&mut self, other: Self) -> Result<(), SyncError>

Merge other into this fence.

The merged fence signals when both inputs have. other is consumed; this fence’s descriptor is replaced by the merged one.

Errors

• SyncError::Empty if either fence holds no descriptor.
• SyncError::MergeReturnedNothing if the ioctl reported success but produced no descriptor.
• SyncError::Io if the ioctl failed.

Trait Implementations

impl Debug for SyncFence

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for SyncFence

fn default() -> Self

Returns the “default value” for a type.