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) { /// let guard = x.lock().unwrap(); /// *guard += 1; /// bar.await; /// } /// ``` /// /// Use instead: /// ```rust,ignore /// use std::sync::Mutex; /// /// async fn foo(x: &Mutex) { /// { /// 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.unwrap_or(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) }