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| 1 | +use crate::utils::{match_type, paths, span_lint_and_help, SpanlessEq}; |
| 2 | +use if_chain::if_chain; |
| 3 | +use rustc_hir::intravisit::{self as visit, NestedVisitorMap, Visitor}; |
| 4 | +use rustc_hir::{Expr, ExprKind, MatchSource}; |
| 5 | +use rustc_lint::{LateContext, LateLintPass}; |
| 6 | +use rustc_middle::hir::map::Map; |
| 7 | +use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| 8 | + |
| 9 | +declare_clippy_lint! { |
| 10 | + /// **What it does:** Checks for `Mutex::lock` calls in `if let` expression |
| 11 | + /// with lock calls in any of the else blocks. |
| 12 | + /// |
| 13 | + /// **Why is this bad?** The Mutex lock remains held for the whole |
| 14 | + /// `if let ... else` block and deadlocks. |
| 15 | + /// |
| 16 | + /// **Known problems:** None. |
| 17 | + /// |
| 18 | + /// **Example:** |
| 19 | + /// |
| 20 | + /// ```rust,ignore |
| 21 | + /// if let Ok(thing) = mutex.lock() { |
| 22 | + /// do_thing(); |
| 23 | + /// } else { |
| 24 | + /// mutex.lock(); |
| 25 | + /// } |
| 26 | + /// ``` |
| 27 | + /// Should be written |
| 28 | + /// ```rust,ignore |
| 29 | + /// let locked = mutex.lock(); |
| 30 | + /// if let Ok(thing) = locked { |
| 31 | + /// do_thing(thing); |
| 32 | + /// } else { |
| 33 | + /// use_locked(locked); |
| 34 | + /// } |
| 35 | + /// ``` |
| 36 | + pub IF_LET_MUTEX, |
| 37 | + correctness, |
| 38 | + "locking a `Mutex` in an `if let` block can cause deadlocks" |
| 39 | +} |
| 40 | + |
| 41 | +declare_lint_pass!(IfLetMutex => [IF_LET_MUTEX]); |
| 42 | + |
| 43 | +impl LateLintPass<'_, '_> for IfLetMutex { |
| 44 | + fn check_expr(&mut self, cx: &LateContext<'_, '_>, ex: &'_ Expr<'_>) { |
| 45 | + let mut arm_visit = ArmVisitor { |
| 46 | + mutex_lock_called: false, |
| 47 | + found_mutex: None, |
| 48 | + cx, |
| 49 | + }; |
| 50 | + let mut op_visit = OppVisitor { |
| 51 | + mutex_lock_called: false, |
| 52 | + found_mutex: None, |
| 53 | + cx, |
| 54 | + }; |
| 55 | + if let ExprKind::Match( |
| 56 | + ref op, |
| 57 | + ref arms, |
| 58 | + MatchSource::IfLetDesugar { |
| 59 | + contains_else_clause: true, |
| 60 | + }, |
| 61 | + ) = ex.kind |
| 62 | + { |
| 63 | + op_visit.visit_expr(op); |
| 64 | + if op_visit.mutex_lock_called { |
| 65 | + for arm in *arms { |
| 66 | + arm_visit.visit_arm(arm); |
| 67 | + } |
| 68 | + |
| 69 | + if arm_visit.mutex_lock_called && arm_visit.same_mutex(cx, op_visit.found_mutex.unwrap()) { |
| 70 | + span_lint_and_help( |
| 71 | + cx, |
| 72 | + IF_LET_MUTEX, |
| 73 | + ex.span, |
| 74 | + "calling `Mutex::lock` inside the scope of another `Mutex::lock` causes a deadlock", |
| 75 | + None, |
| 76 | + "move the lock call outside of the `if let ...` expression", |
| 77 | + ); |
| 78 | + } |
| 79 | + } |
| 80 | + } |
| 81 | + } |
| 82 | +} |
| 83 | + |
| 84 | +/// Checks if `Mutex::lock` is called in the `if let _ = expr. |
| 85 | +pub struct OppVisitor<'tcx, 'l> { |
| 86 | + mutex_lock_called: bool, |
| 87 | + found_mutex: Option<&'tcx Expr<'tcx>>, |
| 88 | + cx: &'tcx LateContext<'tcx, 'l>, |
| 89 | +} |
| 90 | + |
| 91 | +impl<'tcx, 'l> Visitor<'tcx> for OppVisitor<'tcx, 'l> { |
| 92 | + type Map = Map<'tcx>; |
| 93 | + |
| 94 | + fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { |
| 95 | + if_chain! { |
| 96 | + if let Some(mutex) = is_mutex_lock_call(self.cx, expr); |
| 97 | + then { |
| 98 | + self.found_mutex = Some(mutex); |
| 99 | + self.mutex_lock_called = true; |
| 100 | + return; |
| 101 | + } |
| 102 | + } |
| 103 | + visit::walk_expr(self, expr); |
| 104 | + } |
| 105 | + |
| 106 | + fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { |
| 107 | + NestedVisitorMap::None |
| 108 | + } |
| 109 | +} |
| 110 | + |
| 111 | +/// Checks if `Mutex::lock` is called in any of the branches. |
| 112 | +pub struct ArmVisitor<'tcx, 'l> { |
| 113 | + mutex_lock_called: bool, |
| 114 | + found_mutex: Option<&'tcx Expr<'tcx>>, |
| 115 | + cx: &'tcx LateContext<'tcx, 'l>, |
| 116 | +} |
| 117 | + |
| 118 | +impl<'tcx, 'l> Visitor<'tcx> for ArmVisitor<'tcx, 'l> { |
| 119 | + type Map = Map<'tcx>; |
| 120 | + |
| 121 | + fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) { |
| 122 | + if_chain! { |
| 123 | + if let Some(mutex) = is_mutex_lock_call(self.cx, expr); |
| 124 | + then { |
| 125 | + self.found_mutex = Some(mutex); |
| 126 | + self.mutex_lock_called = true; |
| 127 | + return; |
| 128 | + } |
| 129 | + } |
| 130 | + visit::walk_expr(self, expr); |
| 131 | + } |
| 132 | + |
| 133 | + fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { |
| 134 | + NestedVisitorMap::None |
| 135 | + } |
| 136 | +} |
| 137 | + |
| 138 | +impl<'tcx, 'l> ArmVisitor<'tcx, 'l> { |
| 139 | + fn same_mutex(&self, cx: &LateContext<'_, '_>, op_mutex: &Expr<'_>) -> bool { |
| 140 | + if let Some(arm_mutex) = self.found_mutex { |
| 141 | + SpanlessEq::new(cx).eq_expr(op_mutex, arm_mutex) |
| 142 | + } else { |
| 143 | + false |
| 144 | + } |
| 145 | + } |
| 146 | +} |
| 147 | + |
| 148 | +fn is_mutex_lock_call<'a>(cx: &LateContext<'a, '_>, expr: &'a Expr<'_>) -> Option<&'a Expr<'a>> { |
| 149 | + if_chain! { |
| 150 | + if let ExprKind::MethodCall(path, _span, args) = &expr.kind; |
| 151 | + if path.ident.to_string() == "lock"; |
| 152 | + let ty = cx.tables.expr_ty(&args[0]); |
| 153 | + if match_type(cx, ty, &paths::MUTEX); |
| 154 | + then { |
| 155 | + Some(&args[0]) |
| 156 | + } else { |
| 157 | + None |
| 158 | + } |
| 159 | + } |
| 160 | +} |
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