simplify, fix thread-safety

Author: vtjnash

Compiler/src/typeinfer.jl

@@ -1559,9 +1559,6 @@ end
 
 function typeinf_ext_toplevel(interp::AbstractInterpreter, mi::MethodInstance, source_mode::UInt8)
     ci = typeinf_ext(interp, mi, source_mode)
-    if isa(ci, CodeInstance) && ccall(:jl_recording_inference_entrance_backtraces, Cint, ()) != 0
-        ccall(:jl_push_inference_entrance_backtraces, Cvoid, (Any,), ci => backtrace())
-    end
     ci = add_codeinsts_to_jit!(interp, ci, source_mode)
     return ci
 end

doc/src/devdocs/diagnostics.md

@@ -25,3 +25,13 @@ different purposes:
   `ccall`s records a backtrace on every entrance to type-inference, so that
   SnoopCompile can determine the caller of a dynamically-dispatched call. This
   is needed to attribute "cause" for new type inference.
+
+  The `jl_set_inference_entrance_backtraces` function accepts an array where
+  inference entrance events will be recorded. Each inference event stores two
+  consecutive array elements: first the `CodeInstance` object, then the
+  backtrace representation. So for N inference events, the array will contain 2N
+  elements arranged as: `[ci₁, bt₁, ci₂, bt₂, ..., ciₙ, btₙ]`.
+
+  Note that the backtrace elements `btᵢ` contain raw backtrace data that
+  typically needs to be processed using `stacktrace(Base._reformat_bt(btᵢ...))`.
+  to convert them into a usable stack trace format for analysis.

src/gf.c

@@ -492,6 +492,14 @@ jl_code_instance_t *jl_type_infer(jl_method_instance_t *mi, size_t world, uint8_
     if (ci && !jl_is_code_instance(ci)) {
         ci = NULL;
     }
+
+    // Record inference entrance backtrace if enabled
+    if (ci) {
+        JL_GC_PUSH1(&ci);
+        jl_push_inference_entrance_backtraces((jl_value_t*)ci);
+        JL_GC_POP();
+    }
+
     JL_GC_POP();
 #endif
 

src/julia.h

@@ -2276,8 +2276,7 @@ JL_DLLEXPORT jl_value_t *jl_object_top_module(jl_value_t* v) JL_NOTSAFEPOINT;
 JL_DLLEXPORT void jl_set_newly_inferred(jl_value_t *newly_inferred);
 JL_DLLEXPORT void jl_push_newly_inferred(jl_value_t *ci);
 JL_DLLEXPORT void jl_set_inference_entrance_backtraces(jl_value_t *inference_entrance_backtraces);
-JL_DLLEXPORT int jl_recording_inference_entrance_backtraces(void);
-JL_DLLEXPORT void jl_push_inference_entrance_backtraces(jl_value_t *ci_bt_pair);
+JL_DLLEXPORT void jl_push_inference_entrance_backtraces(jl_value_t *ci);
 JL_DLLEXPORT void jl_write_compiler_output(void);
 
 // parsing

src/julia_internal.h

@@ -1506,6 +1506,7 @@ size_t rec_backtrace_ctx(jl_bt_element_t *bt_data, size_t maxsize, bt_context_t
 size_t rec_backtrace_ctx_dwarf(jl_bt_element_t *bt_data, size_t maxsize, bt_context_t *ctx, jl_gcframe_t *pgcstack) JL_NOTSAFEPOINT;
 #endif
 JL_DLLEXPORT jl_value_t *jl_get_backtrace(void);
+JL_DLLEXPORT jl_value_t *jl_backtrace_from_here(int returnsp, int skip);
 void jl_critical_error(int sig, int si_code, bt_context_t *context, jl_task_t *ct);
 JL_DLLEXPORT void jl_raise_debugger(void) JL_NOTSAFEPOINT;
 JL_DLLEXPORT void jl_gdblookup(void* ip) JL_NOTSAFEPOINT;

src/staticdata_utils.c

@@ -142,21 +142,24 @@ JL_DLLEXPORT void jl_set_inference_entrance_backtraces(jl_value_t* _inference_en
     assert(_inference_entrance_backtraces == NULL || _inference_entrance_backtraces == jl_nothing || jl_is_array(_inference_entrance_backtraces));
     if (_inference_entrance_backtraces == jl_nothing)
         _inference_entrance_backtraces = NULL;
+    JL_LOCK(&inference_entrance_backtraces_mutex);
     inference_entrance_backtraces = (jl_array_t*) _inference_entrance_backtraces;
+    JL_UNLOCK(&inference_entrance_backtraces_mutex);
 }
 
-JL_DLLEXPORT int jl_recording_inference_entrance_backtraces(void)
-{
-    return inference_entrance_backtraces != NULL;
-}
 
-JL_DLLEXPORT void jl_push_inference_entrance_backtraces(jl_value_t* ci_bt_pair)
+JL_DLLEXPORT void jl_push_inference_entrance_backtraces(jl_value_t* ci)
 {
-    assert(inference_entrance_backtraces);
     JL_LOCK(&inference_entrance_backtraces_mutex);
+    if (inference_entrance_backtraces == NULL) {
+        JL_UNLOCK(&inference_entrance_backtraces_mutex);
+        return;
+    }
+    jl_value_t* backtrace = jl_backtrace_from_here(0, 1);
     size_t end = jl_array_nrows(inference_entrance_backtraces);
-    jl_array_grow_end(inference_entrance_backtraces, 1);
-    jl_array_ptr_set(inference_entrance_backtraces, end, ci_bt_pair);
+    jl_array_grow_end(inference_entrance_backtraces, 2);
+    jl_array_ptr_set(inference_entrance_backtraces, end, ci);
+    jl_array_ptr_set(inference_entrance_backtraces, end + 1, backtrace);
     JL_UNLOCK(&inference_entrance_backtraces_mutex);
 }
 

test/stacktraces.jl

@@ -279,15 +279,21 @@ end
     ccall(:jl_set_inference_entrance_backtraces, Cvoid, (Any,), nothing)
     ln = @__LINE__() - 2
     fl = Symbol(@__FILE__())
-    @test length(dispatch_backtraces) == 2
+    @test length(dispatch_backtraces) == 4  # 2 ci-backtrace pairs, stored as 4 separate elements
     mcallee, mcaller = only(methods(callee)), only(methods(caller))
-    @test any(dispatch_backtraces) do (ci, trace)
-        ci.def.def === mcallee && any(stacktrace(trace)) do sf
+    # Extract pairs from the flattened array format: ci at odd indices, backtrace at even indices
+    pairs = [(dispatch_backtraces[i], dispatch_backtraces[i+1]) for i in 1:2:length(dispatch_backtraces)]
+    @test any(pairs) do (ci, trace)
+        # trace is a SimpleVector from jl_backtrace_from_here, need to reformat before stacktrace
+        bt = Base._reformat_bt(trace[1], trace[2])
+        ci.def.def === mcallee && any(stacktrace(bt)) do sf
             sf.file == fl && sf.line == ln
         end
     end
-    @test any(dispatch_backtraces) do (ci, trace)
-        ci.def.def === mcaller && any(stacktrace(trace)) do sf
+    @test any(pairs) do (ci, trace)
+        # trace is a SimpleVector from jl_backtrace_from_here, need to reformat before stacktrace
+        bt = Base._reformat_bt(trace[1], trace[2])
+        ci.def.def === mcaller && any(stacktrace(bt)) do sf
             sf.file == fl && sf.line == ln
         end
     end