rust-clippy/clippy_lints/src/await_holding_lock.rs

97 lines
3.6 KiB
Rust

use crate::utils::{match_def_path, paths, span_lint_and_note};
use rustc_hir::def_id::DefId;
use rustc_hir::{AsyncGeneratorKind, Body, BodyId, GeneratorKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty::GeneratorInteriorTypeCause;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::Span;
declare_clippy_lint! {
/// **What it does:** Checks for calls to await while holding a
/// non-async-aware MutexGuard.
///
/// **Why is this bad?** The Mutex types found in syd::sync and parking_lot
/// are not designed to operator in an async context across await points.
///
/// There are two potential solutions. One is to use an asynx-aware Mutex
/// type. Many asynchronous foundation crates provide such a Mutex type. The
/// other solution is to ensure the mutex is unlocked before calling await,
/// either by introducing a scope or an explicit call to Drop::drop.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// ```rust,ignore
/// use std::sync::Mutex;
///
/// async fn foo(x: &Mutex<u32>) {
/// let guard = x.lock().unwrap();
/// *guard += 1;
/// bar.await;
/// }
/// ```
///
/// Use instead:
/// ```rust,ignore
/// use std::sync::Mutex;
///
/// async fn foo(x: &Mutex<u32>) {
/// {
/// let guard = x.lock().unwrap();
/// *guard += 1;
/// }
/// bar.await;
/// }
/// ```
pub AWAIT_HOLDING_LOCK,
pedantic,
"Inside an async function, holding a MutexGuard while calling await"
}
declare_lint_pass!(AwaitHoldingLock => [AWAIT_HOLDING_LOCK]);
impl LateLintPass<'_, '_> for AwaitHoldingLock {
fn check_body(&mut self, cx: &LateContext<'_, '_>, body: &'_ Body<'_>) {
use AsyncGeneratorKind::{Block, Closure, Fn};
match body.generator_kind {
Some(GeneratorKind::Async(Block))
| Some(GeneratorKind::Async(Closure))
| Some(GeneratorKind::Async(Fn)) => {
let body_id = BodyId {
hir_id: body.value.hir_id,
};
let def_id = cx.tcx.hir().body_owner_def_id(body_id);
let tables = cx.tcx.typeck_tables_of(def_id);
check_interior_types(cx, &tables.generator_interior_types, body.value.span);
},
_ => {},
}
}
}
fn check_interior_types(cx: &LateContext<'_, '_>, ty_causes: &[GeneratorInteriorTypeCause<'_>], span: Span) {
for ty_cause in ty_causes {
if let rustc_middle::ty::Adt(adt, _) = ty_cause.ty.kind {
if is_mutex_guard(cx, adt.did) {
span_lint_and_note(
cx,
AWAIT_HOLDING_LOCK,
ty_cause.span,
"this MutexGuard is held across an 'await' point. Consider using an async-aware Mutex type or ensuring the MutexGuard is dropped before calling await.",
ty_cause.scope_span.or(Some(span)),
"these are all the await points this lock is held through",
);
}
}
}
}
fn is_mutex_guard(cx: &LateContext<'_, '_>, def_id: DefId) -> bool {
match_def_path(cx, def_id, &paths::MUTEX_GUARD)
|| match_def_path(cx, def_id, &paths::RWLOCK_READ_GUARD)
|| match_def_path(cx, def_id, &paths::RWLOCK_WRITE_GUARD)
|| match_def_path(cx, def_id, &paths::PARKING_LOT_MUTEX_GUARD)
|| match_def_path(cx, def_id, &paths::PARKING_LOT_RWLOCK_READ_GUARD)
|| match_def_path(cx, def_id, &paths::PARKING_LOT_RWLOCK_WRITE_GUARD)
}