Struct PackLock 

pub struct PackLock { /* private fields */ }

Per-pack file lock wrapper.

Construction via PackLock::open creates (or re-opens) the sidecar <pack_path>/.grex-lock but does not acquire the lock — call PackLock::acquire_async for the async-safe blocking path, PackLock::acquire for the thread-blocking synchronous path, or PackLock::try_acquire for a fail-fast probe.

Implementations

impl PackLock

pub fn open(pack_path: &Path) -> Result<Self, PackLockError>

Open (and create if missing) the sidecar <pack_path>/.grex-lock. Does not acquire the lock.

Errors

Returns PackLockError::Io if the sidecar cannot be opened or its parent directory cannot be created.

pub async fn acquire_async(self) -> Result<PackLockHold, PackLockError>

Async acquire — pairs a process-wide tokio::sync::Mutex keyed by canonical pack path with the sidecar fd-lock. Safe to call from any tokio worker without blocking the runtime. Same-thread re-entry (nested synchronous call chain that re-enters the same pack root, e.g. meta-plugin recursion through a .. child that points back at the parent) returns PackLockError::Busy rather than deadlocking.

The returned PackLockHold drops the fd-lock guard and the async mutex guard in reverse acquire order at end-of-scope.

Errors

• PackLockError::Busy on same-thread re-entry.
• PackLockError::Io on any OS-level lock failure.

pub async fn acquire_cancellable( self, cancel: &CancellationToken, ) -> Result<PackLockHold, PackLockErrorOrCancelled>

Cancellable async acquire — same semantics as PackLock::acquire_async but races the acquire against a tokio_util::sync::CancellationToken. Used by the embedded MCP server (feat-m7-1) so a notifications/cancelled from the client unblocks tool handlers that are parked on a contended pack lock.

Consumes self to mirror PackLock::acquire_async — the same boxed-fd + transmute lifetime dance is needed to hand the guard back across a spawn_blocking boundary, and reusing the consumes-self contract preserves drop ordering against PackLockHold.

OS-thread leak window — contract

fd_lock::write() is a synchronous syscall that parks the calling OS thread until the kernel releases the flock. Once the blocking call has been launched on the tokio::task::spawn_blocking pool, the runtime cannot interrupt it — there is no portable way to unpark a thread blocked in flock(2). When the cancellation token fires we resolve the outer select! with PackLockErrorOrCancelled::Cancelled immediately, but the spawned OS thread stays parked until the holder eventually releases. When that happens, the spawned thread acquires the guard, the JoinHandle resolves to Ok((boxed, guard)), and the tuple is dropped on the spot (because the select! arm has already won) — at which point the guard’s Drop releases the kernel flock and a subsequent acquirer can proceed.

In other words: cancellation is observable to the caller instantly, but the underlying OS thread holds the lock briefly past the cancel point, until the syscall returns. Callers that immediately re-attempt acquire on the same path may see transient contention until that thread drains. See .omne/cfg/mcp.md §Cancellation.

Errors

• PackLockErrorOrCancelled::Cancelled — the token fired before a guard was returned.
• PackLockErrorOrCancelled::Lock wrapping PackLockError::Busy on same-thread re-entry, or PackLockError::Io on any OS-level lock failure.

pub fn acquire(&mut self) -> Result<RwLockWriteGuard<'_, File>, PackLockError>

Thread-blocking acquire (no tokio integration). Waits on the fd-lock synchronously. Suitable for synchronous call sites only — async plugin methods MUST use PackLock::acquire_async to avoid blocking a tokio worker.

Returns a borrowed RwLockWriteGuard; the caller owns both the outer PackLock and the guard in scope. Mirrors the crate::fs::ScopedLock shape.

Errors

Returns PackLockError::Io if the OS lock call fails.

pub fn try_acquire( &mut self, ) -> Result<RwLockWriteGuard<'_, File>, PackLockError>

Non-blocking probe: return PackLockError::Busy instead of waiting when another holder has the lock. Does not engage the async mutex — purely a fail-fast diagnostics hook.

Errors

• PackLockError::Busy when a concurrent holder owns the lock.
• PackLockError::Io on any other OS-level lock failure.

pub fn path(&self) -> &Path

Sidecar path — <pack_path>/.grex-lock.

Trait Implementations

impl Debug for PackLock

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

Formats the value using the given formatter.