diff options
| -rw-r--r-- | CHANGELOG.md | 1 | ||||
| -rw-r--r-- | clippy_lints/src/await_holding_lock.rs | 100 | ||||
| -rw-r--r-- | clippy_lints/src/lib.rs | 4 | ||||
| -rw-r--r-- | src/lintlist/mod.rs | 7 | ||||
| -rw-r--r-- | tests/ui/await_holding_lock.rs | 42 | ||||
| -rw-r--r-- | tests/ui/await_holding_lock.stderr | 35 |
6 files changed, 189 insertions, 0 deletions
diff --git a/CHANGELOG.md b/CHANGELOG.md index d244f8aa167..abd7167502b 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -1188,6 +1188,7 @@ Released 2018-09-13 [`assertions_on_constants`]: https://rust-lang.github.io/rust-clippy/master/index.html#assertions_on_constants [`assign_op_pattern`]: https://rust-lang.github.io/rust-clippy/master/index.html#assign_op_pattern [`assign_ops`]: https://rust-lang.github.io/rust-clippy/master/index.html#assign_ops +[`await_holding_lock`]: https://rust-lang.github.io/rust-clippy/master/index.html#await_holding_lock [`bad_bit_mask`]: https://rust-lang.github.io/rust-clippy/master/index.html#bad_bit_mask [`blacklisted_name`]: https://rust-lang.github.io/rust-clippy/master/index.html#blacklisted_name [`block_in_if_condition_expr`]: https://rust-lang.github.io/rust-clippy/master/index.html#block_in_if_condition_expr diff --git a/clippy_lints/src/await_holding_lock.rs b/clippy_lints/src/await_holding_lock.rs new file mode 100644 index 00000000000..ae4c5bfc9f7 --- /dev/null +++ b/clippy_lints/src/await_holding_lock.rs @@ -0,0 +1,100 @@ +use crate::utils::span_lint_and_note; +use if_chain::if_chain; +use rustc_hir::intravisit::FnKind; +use rustc_hir::{Body, FnDecl, HirId, IsAsync}; +use rustc_lint::{LateContext, LateLintPass}; +use rustc_session::{declare_lint_pass, declare_tool_lint}; +use rustc_span::{Span, Symbol}; + +declare_clippy_lint! { + /// **What it does:** Checks for calls to await while holding a MutexGuard. + /// + /// **Why is this bad?** This is almost certainly an error which can result + /// in a deadlock because the reactor will invoke code not visible to the + /// currently visible scope. + /// + /// **Known problems:** Detects only specifically named guard types: + /// MutexGuard, RwLockReadGuard, and RwLockWriteGuard. + /// + /// **Example:** + /// + /// ```rust + /// use std::sync::Mutex; + /// + /// async fn foo(x: &Mutex<u32>) { + /// let guard = x.lock().unwrap(); + /// *guard += 1; + /// bar.await; + /// } + /// ``` + /// Use instead: + /// ```rust + /// 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" +} + +const MUTEX_GUARD_TYPES: [&str; 3] = ["MutexGuard", "RwLockReadGuard", "RwLockWriteGuard"]; + +declare_lint_pass!(AwaitHoldingLock => [AWAIT_HOLDING_LOCK]); + +impl LateLintPass<'_, '_> for AwaitHoldingLock { + fn check_fn( + &mut self, + cx: &LateContext<'_, '_>, + fn_kind: FnKind<'_>, + _: &FnDecl<'_>, + _: &Body<'_>, + span: Span, + _: HirId, + ) { + if !is_async_fn(fn_kind) { + return; + } + + for ty_clause in &cx.tables.generator_interior_types { + if_chain! { + if let rustc_middle::ty::Adt(adt, _) = ty_clause.ty.kind; + if let Some(&sym) = cx.get_def_path(adt.did).iter().last(); + if is_symbol_mutex_guard(sym); + then { + span_lint_and_note( + cx, + AWAIT_HOLDING_LOCK, + ty_clause.span, + "this MutexGuard is held across an 'await' point", + ty_clause.scope_span.unwrap_or(span), + "these are all the await points this lock is held through" + ); + } + } + } + } +} + +fn is_async_fn(fn_kind: FnKind<'_>) -> bool { + fn_kind.header().map_or(false, |h| match h.asyncness { + IsAsync::Async => true, + IsAsync::NotAsync => false, + }) +} + +fn is_symbol_mutex_guard(sym: Symbol) -> bool { + let sym_str = sym.as_str(); + for ty in &MUTEX_GUARD_TYPES { + if sym_str == *ty { + return true; + } + } + false +} diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs index f3f73835e84..dee4188b75f 100644 --- a/clippy_lints/src/lib.rs +++ b/clippy_lints/src/lib.rs @@ -177,6 +177,7 @@ mod assertions_on_constants; mod assign_ops; mod atomic_ordering; mod attrs; +mod await_holding_lock; mod bit_mask; mod blacklisted_name; mod block_in_if_condition; @@ -497,6 +498,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: &attrs::INLINE_ALWAYS, &attrs::UNKNOWN_CLIPPY_LINTS, &attrs::USELESS_ATTRIBUTE, + &await_holding_lock::AWAIT_HOLDING_LOCK, &bit_mask::BAD_BIT_MASK, &bit_mask::INEFFECTIVE_BIT_MASK, &bit_mask::VERBOSE_BIT_MASK, @@ -864,6 +866,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: ]); // end register lints, do not remove this comment, it’s used in `update_lints` + store.register_late_pass(|| box await_holding_lock::AwaitHoldingLock); store.register_late_pass(|| box serde_api::SerdeAPI); store.register_late_pass(|| box utils::internal_lints::CompilerLintFunctions::new()); store.register_late_pass(|| box utils::internal_lints::LintWithoutLintPass::default()); @@ -1102,6 +1105,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: store.register_group(true, "clippy::pedantic", Some("clippy_pedantic"), vec![ LintId::of(&attrs::INLINE_ALWAYS), + LintId::of(&await_holding_lock::AWAIT_HOLDING_LOCK), LintId::of(&checked_conversions::CHECKED_CONVERSIONS), LintId::of(&copies::MATCH_SAME_ARMS), LintId::of(&copies::SAME_FUNCTIONS_IN_IF_CONDITION), diff --git a/src/lintlist/mod.rs b/src/lintlist/mod.rs index 95931be7341..2c466aa20c6 100644 --- a/src/lintlist/mod.rs +++ b/src/lintlist/mod.rs @@ -53,6 +53,13 @@ pub static ref ALL_LINTS: Vec<Lint> = vec![ module: "assign_ops", }, Lint { + name: "await_holding_lock", + group: "pedantic", + desc: "Inside an async function, holding a MutexGuard while calling await", + deprecation: None, + module: "await_holding_lock", + }, + Lint { name: "bad_bit_mask", group: "correctness", desc: "expressions of the form `_ & mask == select` that will only ever return `true` or `false`", diff --git a/tests/ui/await_holding_lock.rs b/tests/ui/await_holding_lock.rs new file mode 100644 index 00000000000..fab31f37ffc --- /dev/null +++ b/tests/ui/await_holding_lock.rs @@ -0,0 +1,42 @@ +// edition:2018 +#![warn(clippy::await_holding_lock)] + +use std::sync::Mutex; + +async fn bad(x: &Mutex<u32>) -> u32 { + let guard = x.lock().unwrap(); + baz().await +} + +async fn good(x: &Mutex<u32>) -> u32 { + { + let guard = x.lock().unwrap(); + let y = *guard + 1; + } + baz().await; + let guard = x.lock().unwrap(); + 47 +} + +async fn baz() -> u32 { + 42 +} + +async fn also_bad(x: &Mutex<u32>) -> u32 { + let first = baz().await; + + let guard = x.lock().unwrap(); + + let second = baz().await; + + let third = baz().await; + + first + second + third +} + +fn main() { + let m = Mutex::new(100); + good(&m); + bad(&m); + also_bad(&m); +} diff --git a/tests/ui/await_holding_lock.stderr b/tests/ui/await_holding_lock.stderr new file mode 100644 index 00000000000..8d4fd0c20a9 --- /dev/null +++ b/tests/ui/await_holding_lock.stderr @@ -0,0 +1,35 @@ +error: this MutexGuard is held across an 'await' point + --> $DIR/await_holding_lock.rs:7:9 + | +LL | let guard = x.lock().unwrap(); + | ^^^^^ + | + = note: `-D clippy::await-holding-lock` implied by `-D warnings` +note: these are all the await points this lock is held through + --> $DIR/await_holding_lock.rs:7:5 + | +LL | / let guard = x.lock().unwrap(); +LL | | baz().await +LL | | } + | |_^ + +error: this MutexGuard is held across an 'await' point + --> $DIR/await_holding_lock.rs:28:9 + | +LL | let guard = x.lock().unwrap(); + | ^^^^^ + | +note: these are all the await points this lock is held through + --> $DIR/await_holding_lock.rs:28:5 + | +LL | / let guard = x.lock().unwrap(); +LL | | +LL | | let second = baz().await; +LL | | +... | +LL | | first + second + third +LL | | } + | |_^ + +error: aborting due to 2 previous errors + |