[starvation] make analysis work with sil instead of hil

Summary: Subtle false positives and negatives in Hil make Sil preferable. This diff gets rid of the CFG-emulation of Hil, while still using Hil expressions.

Reviewed By: da319

Differential Revision: D23815026

fbshipit-source-id: 731a6d299

infer/src/absint/AbstractDomain.ml

@@ -11,7 +11,7 @@ module F = Format
 module Types = struct
   type 'astate bottom_lifted = Bottom | NonBottom of 'astate
 
-  type 'astate top_lifted = Top | NonTop of 'astate
+  type 'astate top_lifted = Top | NonTop of 'astate [@@deriving equal]
 
   type ('below, 'astate, 'above) below_above = Below of 'below | Above of 'above | Val of 'astate
 end

infer/src/absint/AbstractDomain.mli

@@ -12,7 +12,7 @@ open! IStd
 module Types : sig
   type 'astate bottom_lifted = Bottom | NonBottom of 'astate
 
-  type 'astate top_lifted = Top | NonTop of 'astate
+  type 'astate top_lifted = Top | NonTop of 'astate [@@deriving equal]
 
   type ('below, 'astate, 'above) below_above = Below of 'below | Above of 'above | Val of 'astate
 end

infer/src/backend/StarvationGlobalAnalysis.ml

@@ -12,7 +12,7 @@ module Domain = StarvationDomain
 (* given a scheduled-work item, read the summary of the scheduled method from the disk
    and adapt its contents to the thread it was scheduled too *)
 let get_summary_of_scheduled_work (work_item : Domain.ScheduledWorkItem.t) =
-  let astate = {Domain.bottom with thread= work_item.thread} in
+  let astate = {Domain.initial with thread= work_item.thread} in
   let callsite = CallSite.make work_item.procname work_item.loc in
   let open IOption.Let_syntax in
   let* {Summary.payloads= {starvation}} = Summary.OnDisk.get work_item.procname in

infer/src/concurrency/starvation.ml

@@ -28,6 +28,15 @@ module TransferFunctions (CFG : ProcCfg.S) = struct
       actuals
 
 
+  let hilexp_of_sil ~add_deref (astate : Domain.t) silexp typ =
+    let f_resolve_id var = Domain.VarDomain.get var astate.var_state in
+    HilExp.of_sil ~include_array_indexes:false ~f_resolve_id ~add_deref silexp typ
+
+
+  let hilexp_of_sils ~add_deref astate silexps =
+    List.map silexps ~f:(fun (exp, typ) -> hilexp_of_sil ~add_deref astate exp typ)
+
+
   let rec get_access_expr (hilexp : HilExp.t) =
     match hilexp with
     | AccessExpression access_exp ->
@@ -56,12 +65,14 @@ module TransferFunctions (CFG : ProcCfg.S) = struct
              {acc with attributes} )
     in
     match HilExp.get_access_exprs assume_exp with
-    | [access_expr] when AttributeDomain.is_thread_guard access_expr astate.attributes ->
-        HilExp.eval_boolean_exp access_expr assume_exp
-        |> Option.fold ~init:astate ~f:add_thread_choice
-    | [access_expr] when AttributeDomain.is_future_done_guard access_expr astate.attributes ->
-        HilExp.eval_boolean_exp access_expr assume_exp
-        |> Option.fold ~init:astate ~f:(add_future_done_choice access_expr)
+    | [access_expr] ->
+        if AttributeDomain.is_thread_guard access_expr astate.attributes then
+          HilExp.eval_boolean_exp access_expr assume_exp
+          |> Option.fold ~init:astate ~f:add_thread_choice
+        else if AttributeDomain.is_future_done_guard access_expr astate.attributes then
+          HilExp.eval_boolean_exp access_expr assume_exp
+          |> Option.fold ~init:astate ~f:(add_future_done_choice access_expr)
+        else astate
     | _ ->
         astate
 
@@ -214,8 +225,33 @@ module TransferFunctions (CFG : ProcCfg.S) = struct
     |> Option.value ~default:astate
 
 
+  let do_metadata (metadata : Sil.instr_metadata) astate =
+    match metadata with ExitScope (vars, _) -> Domain.remove_dead_vars astate vars | _ -> astate
+
+
+  let do_load tenv ~lhs rhs_exp rhs_typ (astate : Domain.t) =
+    let lhs_var = fst lhs in
+    let add_deref = match (lhs_var : Var.t) with LogicalVar _ -> true | ProgramVar _ -> false in
+    let rhs_hil_exp = hilexp_of_sil ~add_deref astate rhs_exp rhs_typ in
+    let astate =
+      get_access_expr rhs_hil_exp
+      |> Option.value_map ~default:astate ~f:(fun acc_exp ->
+             {astate with var_state= Domain.VarDomain.set lhs_var acc_exp astate.var_state} )
+    in
+    let lhs_hil_acc_exp = HilExp.AccessExpression.base lhs in
+    do_assignment tenv lhs_hil_acc_exp rhs_hil_exp astate
+
+
+  let do_cast tenv id base_typ actuals astate =
+    match actuals with
+    | [(e, typ); _sizeof] ->
+        do_load tenv ~lhs:(Var.of_id id, base_typ) e typ astate
+    | _ ->
+        astate
+
+
   let exec_instr (astate : Domain.t) ({interproc= {proc_desc; tenv}; formals} as analysis_data) _
-      (instr : HilInstr.t) =
+      instr =
     let open ConcurrencyModels in
     let open StarvationModels in
     let get_lock_path = Domain.Lock.make formals in
@@ -225,68 +261,84 @@ module TransferFunctions (CFG : ProcCfg.S) = struct
       List.filter_map ~f:get_lock_path locks |> Domain.acquire ~tenv astate ~procname ~loc
     in
     let do_unlock locks astate = List.filter_map ~f:get_lock_path locks |> Domain.release astate in
-    match instr with
-    | Assign (lhs_access_exp, rhs_exp, _) ->
-        do_assignment tenv lhs_access_exp rhs_exp astate
-    | Metadata (Sil.ExitScope (vars, _)) ->
-        {astate with attributes= Domain.AttributeDomain.exit_scope vars astate.attributes}
-    | Metadata _ ->
-        astate
-    | Assume (assume_exp, _, _, _) ->
-        do_assume assume_exp astate
-    | Call (_, Indirect _, _, _, _) ->
+    match (instr : Sil.instr) with
+    | Metadata metadata ->
+        do_metadata metadata astate
+    | Prune (exp, _loc, _then_branch, _if_kind) ->
+        let hil_exp = hilexp_of_sil ~add_deref:false astate exp Typ.boolean in
+        do_assume hil_exp astate
+    | Load {id} when Ident.is_none id ->
         astate
-    | Call (_, Direct callee, actuals, _, _) when should_skip_analysis tenv callee actuals ->
+    | Load {id; e; typ} ->
+        do_load tenv ~lhs:(Var.of_id id, typ) e typ astate
+    | Store {e1= Lvar lhs_pvar; typ; e2} when Pvar.is_ssa_frontend_tmp lhs_pvar ->
+        do_load tenv ~lhs:(Var.of_pvar lhs_pvar, typ) e2 typ astate
+    | Store {e1; typ; e2} ->
+        let rhs_hil_exp = hilexp_of_sil ~add_deref:false astate e2 typ in
+        hilexp_of_sil ~add_deref:true astate e1 (Typ.mk_ptr typ)
+        |> get_access_expr
+        |> Option.value_map ~default:astate ~f:(fun lhs_hil_acc_exp ->
+               do_assignment tenv lhs_hil_acc_exp rhs_hil_exp astate )
+    | Call (_, Const (Cfun callee), actuals, _, _)
+      when should_skip_analysis tenv callee (hilexp_of_sils ~add_deref:false astate actuals) ->
         astate
-    | Call (ret_base, Direct callee, actuals, _, loc) -> (
-      match get_lock_effect callee actuals with
-      | Lock locks ->
-          do_lock locks loc astate
-      | GuardLock guard ->
-          Domain.lock_guard tenv astate guard ~procname ~loc
-      | GuardConstruct {guard; lock; acquire_now} -> (
-        match get_lock_path lock with
-        | Some lock_path ->
-            Domain.add_guard tenv astate guard lock_path ~acquire_now ~procname ~loc
-        | None ->
-            log_parse_error "Couldn't parse lock in guard constructor" callee actuals ;
-            astate )
-      | Unlock locks ->
-          do_unlock locks astate
-      | GuardUnlock guard ->
-          Domain.unlock_guard astate guard
-      | GuardDestroy guard ->
-          Domain.remove_guard astate guard
-      | LockedIfTrue _ | GuardLockedIfTrue _ ->
-          astate
-      | NoEffect when is_synchronized_library_call tenv callee ->
-          (* model a synchronized call without visible internal behaviour *)
-          let locks = List.hd actuals |> Option.to_list in
-          do_lock locks loc astate |> do_unlock locks
-      | NoEffect when is_java && is_strict_mode_violation tenv callee actuals ->
-          Domain.strict_mode_call ~callee ~loc astate
-      | NoEffect when is_java && is_monitor_wait tenv callee actuals ->
-          Domain.wait_on_monitor ~loc formals actuals astate
-      | NoEffect when is_java && is_future_get tenv callee actuals ->
-          Domain.future_get ~callee ~loc actuals astate
-      | NoEffect when is_java -> (
-          let ret_exp = HilExp.AccessExpression.base ret_base in
-          let astate = do_work_scheduling tenv callee actuals loc astate in
-          match may_block tenv callee actuals with
-          | Some sev ->
-              Domain.blocking_call ~callee sev ~loc astate
+    | Call ((id, base_typ), Const (Cfun callee), actuals, _, _)
+      when Procname.equal callee BuiltinDecl.__cast ->
+        do_cast tenv id base_typ actuals astate
+    | Call ((id, typ), Const (Cfun callee), sil_actuals, loc, _) -> (
+        let ret_base = (Var.of_id id, typ) in
+        let actuals = hilexp_of_sils ~add_deref:false astate sil_actuals in
+        match get_lock_effect callee actuals with
+        | Lock locks ->
+            do_lock locks loc astate
+        | GuardLock guard ->
+            Domain.lock_guard tenv astate guard ~procname ~loc
+        | GuardConstruct {guard; lock; acquire_now} -> (
+          match get_lock_path lock with
+          | Some lock_path ->
+              Domain.add_guard tenv astate guard lock_path ~acquire_now ~procname ~loc
           | None ->
-              do_call analysis_data ret_exp callee actuals loc astate )
-      | NoEffect ->
-          (* in C++/Obj C we only care about deadlocks, not starvation errors *)
-          let ret_exp = HilExp.AccessExpression.base ret_base in
-          do_call analysis_data ret_exp callee actuals loc astate )
+              log_parse_error "Couldn't parse lock in guard constructor" callee actuals ;
+              astate )
+        | Unlock locks ->
+            do_unlock locks astate
+        | GuardUnlock guard ->
+            Domain.unlock_guard astate guard
+        | GuardDestroy guard ->
+            Domain.remove_guard astate guard
+        | LockedIfTrue _ | GuardLockedIfTrue _ ->
+            astate
+        | NoEffect when is_synchronized_library_call tenv callee ->
+            (* model a synchronized call without visible internal behaviour *)
+            let locks = List.hd actuals |> Option.to_list in
+            do_lock locks loc astate |> do_unlock locks
+        | NoEffect when is_java && is_strict_mode_violation tenv callee actuals ->
+            Domain.strict_mode_call ~callee ~loc astate
+        | NoEffect when is_java && is_monitor_wait tenv callee actuals ->
+            Domain.wait_on_monitor ~loc formals actuals astate
+        | NoEffect when is_java && is_future_get tenv callee actuals ->
+            Domain.future_get ~callee ~loc actuals astate
+        | NoEffect when is_java -> (
+            let ret_exp = HilExp.AccessExpression.base ret_base in
+            let astate = do_work_scheduling tenv callee actuals loc astate in
+            match may_block tenv callee actuals with
+            | Some sev ->
+                Domain.blocking_call ~callee sev ~loc astate
+            | None ->
+                do_call analysis_data ret_exp callee actuals loc astate )
+        | NoEffect ->
+            (* in C++/Obj C we only care about deadlocks, not starvation errors *)
+            let ret_exp = HilExp.AccessExpression.base ret_base in
+            do_call analysis_data ret_exp callee actuals loc astate )
+    | Call ((id, _), _, _, _, _) ->
+        (* call havocs LHS *)
+        Domain.remove_dead_vars astate [Var.of_id id]
 
 
   let pp_session_name _node fmt = F.pp_print_string fmt "starvation"
 end
 
-module Analyzer = LowerHil.MakeAbstractInterpreter (TransferFunctions (ProcCfg.Normal))
+module Analyzer = AbstractInterpreter.MakeRPO (TransferFunctions (ProcCfg.Normal))
 
 (** Compute the attributes (of static variables) set up by the class initializer. *)
 let set_class_init_attributes procname (astate : Domain.t) =
@@ -378,7 +430,7 @@ let analyze_procedure ({InterproceduralAnalysis.proc_desc; tenv} as interproc) =
       else Fn.id
     in
     let initial =
-      Domain.bottom
+      Domain.initial
       (* set the attributes of instance variables set up by all constructors or the class initializer *)
       |> set_initial_attributes interproc
       |> set_lock_state_for_synchronized_proc |> set_thread_status_by_annotation

infer/src/concurrency/starvationDomain.ml

@@ -109,6 +109,54 @@ module Lock = struct
     String.compare (mk_str t1) (mk_str t2)
 end
 
+module AccessExpressionDomain = struct
+  open AbstractDomain.Types
+
+  type t = HilExp.AccessExpression.t top_lifted [@@deriving equal]
+
+  let pp fmt = function
+    | Top ->
+        F.pp_print_string fmt "AccExpTop"
+    | NonTop lock ->
+        HilExp.AccessExpression.pp fmt lock
+
+
+  let top = Top
+
+  let is_top = function Top -> true | NonTop _ -> false
+
+  let join lhs rhs = if equal lhs rhs then lhs else top
+
+  let leq ~lhs ~rhs = equal (join lhs rhs) rhs
+
+  let widen ~prev ~next ~num_iters:_ = join prev next
+end
+
+module VarDomain = struct
+  include AbstractDomain.SafeInvertedMap (Var) (AccessExpressionDomain)
+
+  let exit_scope init deadvars =
+    List.fold deadvars ~init ~f:(fun acc deadvar ->
+        filter
+          (fun _key acc_exp_opt ->
+            match acc_exp_opt with
+            | Top ->
+                (* should never happen in a safe inverted map *)
+                false
+            | NonTop acc_exp ->
+                let var, _ = HilExp.AccessExpression.get_base acc_exp in
+                not (Var.equal var deadvar) )
+          acc
+        |> remove deadvar )
+
+
+  let get var astate =
+    match find_opt var astate with None | Some Top -> None | Some (NonTop x) -> Some x
+
+
+  let set var acc_exp astate = add var (NonTop acc_exp) astate
+end
+
 module Event = struct
   type t =
     | LockAcquire of Lock.t
@@ -598,33 +646,26 @@ type t =
   ; critical_pairs: CriticalPairs.t
   ; attributes: AttributeDomain.t
   ; thread: ThreadDomain.t
-  ; scheduled_work: ScheduledWorkDomain.t }
+  ; scheduled_work: ScheduledWorkDomain.t
+  ; var_state: VarDomain.t }
 
-let bottom =
+let initial =
   { guard_map= GuardToLockMap.empty
   ; lock_state= LockState.top
   ; critical_pairs= CriticalPairs.empty
   ; attributes= AttributeDomain.empty
   ; thread= ThreadDomain.bottom
-  ; scheduled_work= ScheduledWorkDomain.bottom }
-
-
-let is_bottom astate =
-  GuardToLockMap.is_empty astate.guard_map
-  && LockState.is_top astate.lock_state
-  && CriticalPairs.is_empty astate.critical_pairs
-  && AttributeDomain.is_top astate.attributes
-  && ThreadDomain.is_bottom astate.thread
-  && ScheduledWorkDomain.is_bottom astate.scheduled_work
+  ; scheduled_work= ScheduledWorkDomain.bottom
+  ; var_state= VarDomain.top }
 
 
 let pp fmt astate =
   F.fprintf fmt
     "{guard_map= %a; lock_state= %a; critical_pairs= %a; attributes= %a; thread= %a; \
-     scheduled_work= %a}"
+     scheduled_work= %a; var_state= %a}"
     GuardToLockMap.pp astate.guard_map LockState.pp astate.lock_state CriticalPairs.pp
     astate.critical_pairs AttributeDomain.pp astate.attributes ThreadDomain.pp astate.thread
-    ScheduledWorkDomain.pp astate.scheduled_work
+    ScheduledWorkDomain.pp astate.scheduled_work VarDomain.pp astate.var_state
 
 
 let join lhs rhs =
@@ -633,7 +674,8 @@ let join lhs rhs =
   ; critical_pairs= CriticalPairs.join lhs.critical_pairs rhs.critical_pairs
   ; attributes= AttributeDomain.join lhs.attributes rhs.attributes
   ; thread= ThreadDomain.join lhs.thread rhs.thread
-  ; scheduled_work= ScheduledWorkDomain.join lhs.scheduled_work rhs.scheduled_work }
+  ; scheduled_work= ScheduledWorkDomain.join lhs.scheduled_work rhs.scheduled_work
+  ; var_state= VarDomain.join lhs.var_state rhs.var_state }
 
 
 let widen ~prev ~next ~num_iters:_ = join prev next
@@ -645,6 +687,7 @@ let leq ~lhs ~rhs =
   && AttributeDomain.leq ~lhs:lhs.attributes ~rhs:rhs.attributes
   && ThreadDomain.leq ~lhs:lhs.thread ~rhs:rhs.thread
   && ScheduledWorkDomain.leq ~lhs:lhs.scheduled_work ~rhs:rhs.scheduled_work
+  && VarDomain.leq ~lhs:lhs.var_state ~rhs:rhs.var_state
 
 
 let add_critical_pair ?tenv lock_state event thread ~loc acc =
@@ -825,3 +868,16 @@ let summary_of_astate : Procdesc.t -> t -> summary =
   ; scheduled_work= astate.scheduled_work
   ; attributes
   ; return_attribute }
+
+
+let remove_dead_vars (astate : t) deadvars =
+  let deadvars =
+    (* The liveness analysis will kill any variable (such as [this]) immediately after its
+       last use. This is bad for attributes that need to live until the end of the method,
+       so we restrict to SSA variables. *)
+    List.rev_filter deadvars ~f:(fun (v : Var.t) ->
+        match v with LogicalVar _ -> true | ProgramVar pvar -> Pvar.is_ssa_frontend_tmp pvar )
+  in
+  let var_state = VarDomain.exit_scope astate.var_state deadvars in
+  let attributes = AttributeDomain.exit_scope deadvars astate.attributes in
+  {astate with var_state; attributes}

infer/src/concurrency/starvationDomain.mli

@@ -45,6 +45,16 @@ module Lock : sig
   (** a stable order for avoiding reporting deadlocks twice based on the root variable type *)
 end
 
+module VarDomain : sig
+  include AbstractDomain.WithTop
+
+  type key = Var.t
+
+  val get : key -> t -> HilExp.AccessExpression.t option
+
+  val set : key -> HilExp.AccessExpression.t -> t -> t
+end
+
 module Event : sig
   type t =
     | LockAcquire of Lock.t
@@ -140,8 +150,6 @@ module AttributeDomain : sig
 
   val is_future_done_guard : HilExp.AccessExpression.t -> t -> bool
   (** does the given expr has attribute [FutureDone x] return [Some x] else [None] *)
-
-  val exit_scope : Var.t list -> t -> t
 end
 
 (** A record of scheduled parallel work: the method scheduled to run, where, and on what thread. *)
@@ -159,9 +167,13 @@ type t =
   ; critical_pairs: CriticalPairs.t
   ; attributes: AttributeDomain.t
   ; thread: ThreadDomain.t
-  ; scheduled_work: ScheduledWorkDomain.t }
+  ; scheduled_work: ScheduledWorkDomain.t
+  ; var_state: VarDomain.t }
 
-include AbstractDomain.WithBottom with type t := t
+include AbstractDomain.S with type t := t
+
+val initial : t
+(** initial domain state *)
 
 val acquire : ?tenv:Tenv.t -> t -> procname:Procname.t -> loc:Location.t -> Lock.t list -> t
 (** simultaneously acquire a number of locks, no-op if list is empty *)
@@ -226,3 +238,5 @@ val integrate_summary :
 val summary_of_astate : Procdesc.t -> t -> summary
 
 val filter_blocking_calls : t -> t
+
+val remove_dead_vars : t -> Var.t list -> t

infer/tests/codetoanalyze/java/starvation/ThreadDeadlock.java

@@ -82,17 +82,16 @@ class ThreadDeadlock {
 
   Object lockE, lockF, lockG;
 
-  public void FP_sequentialEandGOk() {
+  public void sequentialEandGOk() {
     synchronized (lockE) {
       synchronized (lockF) {
       }
     }
-    // at this point we still believe lockE is held
     synchronized (lockG) {
     }
   }
 
-  public void FP_nestedGthenEOk() {
+  public void nestedGthenEOk() {
     synchronized (lockG) {
       synchronized (lockE) {
       }

infer/tests/codetoanalyze/java/starvation/issues.exp

@@ -78,8 +78,6 @@ codetoanalyze/java/starvation/ThreadCalls.java, ThreadCalls.indirectJoinOnUIThre
 codetoanalyze/java/starvation/ThreadCalls.java, ThreadCalls.indirectSleepOnUIThreadBad():void, 24, STARVATION, no_bucket, ERROR, [[Trace 1] `void ThreadCalls.indirectSleepOnUIThreadBad()`, locks `this.lock` in `class ThreadCalls`,[Trace 2] `void ThreadCalls.lockAndSleepOnNonUIThread()`, locks `this.lock` in `class ThreadCalls`,Method call: `void ThreadCalls.sleepOnAnyThreadOk()`,calls `void Thread.sleep(long)`]
 codetoanalyze/java/starvation/ThreadCalls.java, ThreadCalls.joinOnUIThreadBad(java.lang.Thread):void, 40, STARVATION, no_bucket, ERROR, [`void ThreadCalls.joinOnUIThreadBad(Thread)`,calls `void Thread.join()`]
 codetoanalyze/java/starvation/ThreadCalls.java, ThreadCalls.sleepOnUIThreadBad():void, 17, STARVATION, no_bucket, ERROR, [`void ThreadCalls.sleepOnUIThreadBad()`,calls `void Thread.sleep(long)`]
-codetoanalyze/java/starvation/ThreadDeadlock.java, ThreadDeadlock.FP_nestedGthenEOk():void, 96, DEADLOCK, no_bucket, ERROR, [[Trace 1] `void ThreadDeadlock.FP_nestedGthenEOk()`, locks `this.lockG` in `class ThreadDeadlock`, locks `this.lockE` in `class ThreadDeadlock`,[Trace 2] `void ThreadDeadlock.FP_sequentialEandGOk()`, locks `this.lockE` in `class ThreadDeadlock`, locks `this.lockG` in `class ThreadDeadlock`]
-codetoanalyze/java/starvation/ThreadDeadlock.java, ThreadDeadlock.FP_sequentialEandGOk():void, 86, DEADLOCK, no_bucket, ERROR, [[Trace 1] `void ThreadDeadlock.FP_sequentialEandGOk()`, locks `this.lockE` in `class ThreadDeadlock`, locks `this.lockG` in `class ThreadDeadlock`,[Trace 2] `void ThreadDeadlock.FP_nestedGthenEOk()`, locks `this.lockG` in `class ThreadDeadlock`, locks `this.lockE` in `class ThreadDeadlock`]
 codetoanalyze/java/starvation/ThreadDeadlock.java, ThreadDeadlock.annotatedUiThreadBad():void, 35, DEADLOCK, no_bucket, ERROR, [[Trace 1] `void ThreadDeadlock.annotatedUiThreadBad()`, locks `this` in `class ThreadDeadlock`, locks `this.lockB` in `class ThreadDeadlock`,[Trace 2] `void ThreadDeadlock.annotatedWorkerThreadBad()`, locks `this.lockB` in `class ThreadDeadlock`, locks `this` in `class ThreadDeadlock`]
 codetoanalyze/java/starvation/ThreadDeadlock.java, ThreadDeadlock.annotatedWorkerThreadBad():void, 42, DEADLOCK, no_bucket, ERROR, [[Trace 1] `void ThreadDeadlock.annotatedWorkerThreadBad()`, locks `this.lockB` in `class ThreadDeadlock`, locks `this` in `class ThreadDeadlock`,[Trace 2] `void ThreadDeadlock.annotatedUiThreadBad()`, locks `this` in `class ThreadDeadlock`, locks `this.lockB` in `class ThreadDeadlock`]
 codetoanalyze/java/starvation/ThreadDeadlock.java, ThreadDeadlock.assertOnBackgroundThreadBad():void, 60, DEADLOCK, no_bucket, ERROR, [[Trace 1] `void ThreadDeadlock.assertOnBackgroundThreadBad()`, locks `this.lockC` in `class ThreadDeadlock`, locks `this` in `class ThreadDeadlock`,[Trace 2] `void ThreadDeadlock.assertOnUIThreadBad()`, locks `this` in `class ThreadDeadlock`, locks `this.lockC` in `class ThreadDeadlock`]