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//! Ranks for `wgpu-core` locks, restricting acquisition order.
//!
//! See [`LockRank`].
/// The rank of a lock.
///
/// Each [`Mutex`], [`RwLock`], and [`SnatchLock`] in `wgpu-core` has been
/// assigned a *rank*: a node in the DAG defined at the bottom of
/// `wgpu-core/src/lock/rank.rs`. The rank of the most recently
/// acquired lock you are still holding determines which locks you may
/// attempt to acquire next.
///
/// When you create a lock in `wgpu-core`, you must specify its rank
/// by passing in a [`LockRank`] value. This module declares a
/// pre-defined set of ranks to cover everything in `wgpu-core`, named
/// after the type in which they occur, and the name of the type's
/// field that is a lock. For example, [`CommandBuffer::data`] is a
/// `Mutex`, and its rank here is the constant
/// [`COMMAND_BUFFER_DATA`].
///
/// [`Mutex`]: parking_lot::Mutex
/// [`RwLock`]: parking_lot::RwLock
/// [`SnatchLock`]: crate::snatch::SnatchLock
/// [`CommandBuffer::data`]: crate::command::CommandBuffer::data
#[derive(Debug, Copy, Clone)]
pub struct LockRank {
/// The bit representing this lock.
///
/// There should only be a single bit set in this value.
pub(super) bit: LockRankSet,
/// A bitmask of permitted successor ranks.
///
/// If `rank` is the rank of the most recently acquired lock we
/// are still holding, then `rank.followers` is the mask of
/// locks we are allowed to acquire next.
///
/// The `define_lock_ranks!` macro ensures that there are no
/// cycles in the graph of lock ranks and their followers.
pub(super) followers: LockRankSet,
}
/// Define a set of lock ranks, and each rank's permitted successors.
macro_rules! define_lock_ranks {
{
$(
$( #[ $attr:meta ] )*
rank $name:ident $member:literal followed by { $( $follower:ident ),* $(,)? }
)*
} => {
// An enum that assigns a unique number to each rank.
#[allow(non_camel_case_types, clippy::upper_case_acronyms)]
enum LockRankNumber { $( $name, )* }
bitflags::bitflags! {
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
/// A bitflags type representing a set of lock ranks.
pub struct LockRankSet: u64 {
$(
const $name = 1 << (LockRankNumber:: $name as u64);
)*
}
}
impl LockRankSet {
pub fn member_name(self) -> &'static str {
match self {
$(
LockRankSet:: $name => $member,
)*
_ => "<unrecognized LockRankSet bit>",
}
}
#[cfg_attr(not(feature = "observe_locks"), allow(dead_code))]
pub fn const_name(self) -> &'static str {
match self {
$(
LockRankSet:: $name => stringify!($name),
)*
_ => "<unrecognized LockRankSet bit>",
}
}
}
$(
// If there is any cycle in the ranking, the initializers
// for `followers` will be cyclic, and rustc will give us
// an error message explaining the cycle.
$( #[ $attr ] )*
pub const $name: LockRank = LockRank {
bit: LockRankSet:: $name,
followers: LockRankSet::empty() $( .union($follower.bit) )*,
};
)*
}
}
define_lock_ranks! {
rank COMMAND_BUFFER_DATA "CommandBuffer::data" followed by {
DEVICE_SNATCHABLE_LOCK,
DEVICE_USAGE_SCOPES,
SHARED_TRACKER_INDEX_ALLOCATOR_INNER,
BUFFER_MAP_STATE,
}
rank DEVICE_SNATCHABLE_LOCK "Device::snatchable_lock" followed by {
SHARED_TRACKER_INDEX_ALLOCATOR_INNER,
DEVICE_TRACE,
BUFFER_MAP_STATE,
// Uncomment this to see an interesting cycle.
// COMMAND_BUFFER_DATA,
}
rank BUFFER_MAP_STATE "Buffer::map_state" followed by {
DEVICE_PENDING_WRITES,
SHARED_TRACKER_INDEX_ALLOCATOR_INNER,
DEVICE_TRACE,
}
rank DEVICE_PENDING_WRITES "Device::pending_writes" followed by {
COMMAND_ALLOCATOR_FREE_ENCODERS,
SHARED_TRACKER_INDEX_ALLOCATOR_INNER,
DEVICE_LIFE_TRACKER,
}
rank DEVICE_LIFE_TRACKER "Device::life_tracker" followed by {
COMMAND_ALLOCATOR_FREE_ENCODERS,
DEVICE_TRACE,
}
rank COMMAND_ALLOCATOR_FREE_ENCODERS "CommandAllocator::free_encoders" followed by {
SHARED_TRACKER_INDEX_ALLOCATOR_INNER,
}
rank BUFFER_BIND_GROUPS "Buffer::bind_groups" followed by { }
rank BUFFER_INITIALIZATION_STATUS "Buffer::initialization_status" followed by { }
rank DEVICE_DEFERRED_DESTROY "Device::deferred_destroy" followed by { }
rank DEVICE_FENCE "Device::fence" followed by { }
#[allow(dead_code)]
rank DEVICE_TRACE "Device::trace" followed by { }
rank DEVICE_TRACKERS "Device::trackers" followed by { }
rank DEVICE_USAGE_SCOPES "Device::usage_scopes" followed by { }
rank IDENTITY_MANAGER_VALUES "IdentityManager::values" followed by { }
rank REGISTRY_STORAGE "Registry::storage" followed by { }
rank RESOURCE_POOL_INNER "ResourcePool::inner" followed by { }
rank SHARED_TRACKER_INDEX_ALLOCATOR_INNER "SharedTrackerIndexAllocator::inner" followed by { }
rank SURFACE_PRESENTATION "Surface::presentation" followed by { }
rank TEXTURE_BIND_GROUPS "Texture::bind_groups" followed by { }
rank TEXTURE_INITIALIZATION_STATUS "Texture::initialization_status" followed by { }
rank TEXTURE_VIEWS "Texture::views" followed by { }
#[cfg(test)]
rank PAWN "pawn" followed by { ROOK, BISHOP }
#[cfg(test)]
rank ROOK "rook" followed by { KNIGHT }
#[cfg(test)]
rank KNIGHT "knight" followed by { }
#[cfg(test)]
rank BISHOP "bishop" followed by { }
}