use synchronous reads for call stack computation, but extend artifact cache with the ability to say that a non-retryable failure occurred, so that we can fall back to stale call stacks

src/dbg_engine/dbg_engine_ctrl.c

@@ -1781,9 +1781,10 @@ d_unwind_from_thread(Arena *arena, D_Handle thread, U64 endt_us)
   D_Unwind unwind = { .flags = D_UnwindFlag_Error };
   
   //////////////////////////////
-  //- rjf: grab run state pre-unwind computing
+  //- rjf: grab generations pre-unwind computing
   //
-  U64 run_gen = d_run_gen();
+  U64 mem_gen = d_mem_gen();
+  U64 reg_gen = d_reg_gen();
   
   //////////////////////////////
   //- rjf: unpack args
@@ -1889,19 +1890,16 @@ d_unwind_from_thread(Arena *arena, D_Handle thread, U64 endt_us)
         // stale. if it can't be read, the unwind fails.
         if(step.status == UWND_StepStatus_FailedMemoryRead)
         {
-          D_ProcessMemorySlice slice = d_process_memory_slice_from_vaddr_range(scratch.arena, process_entity->handle, step.missed_read_vaddr_range, 1, endt_us);
-          String8 data = slice.data;
-          if(slice.stale)
+          U64 size_desired = dim_1u64(step.missed_read_vaddr_range);
+          U8 *data = push_array(scratch.arena, U8, size_desired);
+          U64 size = d_process_read(process_entity->handle, step.missed_read_vaddr_range, data);
+          if(size == size_desired)
           {
-            unwind.flags |= D_UnwindFlag_Stale;
-          }
-          else if(data.size < dim_1u64(step.missed_read_vaddr_range))
-          {
-            unwind.flags |= D_UnwindFlag_Error;
+            memory_map_push(scratch.arena, &memory_map, step.missed_read_vaddr_range, data);
           }
           else
           {
-            memory_map_push(scratch.arena, &memory_map, step.missed_read_vaddr_range, data.str);
+            unwind.flags |= D_UnwindFlag_Error;
           }
         }
         
@@ -1949,6 +1947,18 @@ d_unwind_from_thread(Arena *arena, D_Handle thread, U64 endt_us)
     }
   }
   
+  //- rjf: if we failed, but our generations changed, mark the 'stale' bit
+  if(unwind.flags & D_UnwindFlag_Error)
+  {
+    U64 post_reg_gen = d_reg_gen();
+    U64 post_mem_gen = d_mem_gen();
+    if(post_reg_gen != reg_gen ||
+       post_mem_gen != mem_gen)
+    {
+      unwind.flags |= D_UnwindFlag_Stale;
+    }
+  }
+  
   //- rjf: bake frames list into result array
   {
     unwind.frames.count = frame_node_count;
@@ -5626,7 +5636,7 @@ d_data_from_process_vaddr_range(Arena *arena, D_Handle process, Rng1U64 vaddr_ra
 //- rjf: process memory artifact cache
 
 internal AC_Artifact
-d_memory_artifact_create(String8 key, B32 *cancel_signal, B32 *retry_out, U64 *gen_out)
+d_memory_artifact_create(String8 key, B32 *cancel_signal, AC_Status *status_out, U64 *gen_out)
 {
   AC_Artifact artifact = {0};
   {
@@ -5768,7 +5778,7 @@ d_memory_artifact_create(String8 key, B32 *cancel_signal, B32 *retry_out, U64 *g
     //- rjf: retry on mem gen "tearing", and if the range is non-empty
     if(pre_read_mem_gen != post_read_mem_gen && range_size != 0)
     {
-      retry_out[0] = 1;
+      status_out[0] = AC_Status_NeedRetry;
     }
     
     //- rjf: bundle content key as artifact
@@ -5981,7 +5991,7 @@ d_process_memory_read(D_Handle process, Rng1U64 range, B32 *is_stale_out, void *
 //~ rjf: TLS Address Artifact Cache Hooks / Lookups
 
 internal AC_Artifact
-d_tls_vaddr_artifact_create(String8 key, B32 *cancel_signal, B32 *retry_out, U64 *gen_out)
+d_tls_vaddr_artifact_create(String8 key, B32 *cancel_signal, AC_Status *status_out, U64 *gen_out)
 {
   // rjf: unpack key
   D_Handle thread = {0};
@@ -6008,7 +6018,7 @@ d_tls_vaddr_artifact_create(String8 key, B32 *cancel_signal, B32 *retry_out, U64
   // rjf: if not successful -> retry
   if(!success)
   {
-    retry_out[0] = 1;
+    status_out[0] = AC_Status_NeedRetry;
   }
   
   // rjf: package as artifact
@@ -6017,11 +6027,6 @@ d_tls_vaddr_artifact_create(String8 key, B32 *cancel_signal, B32 *retry_out, U64
   return artifact;
 }
 
-internal void d_tls_vaddr_artifact_destroy(AC_Artifact artifact)
-{
-  // NOTE(rjf): no-op
-}
-
 internal U64
 d_cached_tls_vaddr_from_thread_module(D_Handle thread_handle, D_Handle module_handle, U64 endt_us, B32 *stale_out)
 {
@@ -6029,7 +6034,7 @@ d_cached_tls_vaddr_from_thread_module(D_Handle thread_handle, D_Handle module_ha
   Access *access = access_open();
   D_Handle key_data[] = {thread_handle, module_handle};
   String8 key = str8((U8 *)&key_data[0], sizeof(key_data));
-  AC_Artifact artifact = ac_artifact_from_key(access, key, d_tls_vaddr_artifact_create, d_tls_vaddr_artifact_destroy, endt_us, .stale_out = stale_out);
+  AC_Artifact artifact = ac_artifact_from_key(access, key, d_tls_vaddr_artifact_create, 0, endt_us, .stale_out = stale_out);
   result = artifact.u64[0];
   access_close(access);
   return result;
@@ -6039,7 +6044,7 @@ d_cached_tls_vaddr_from_thread_module(D_Handle thread_handle, D_Handle module_ha
 //~ rjf: Call Stack Artifact Cache Hooks / Lookups
 
 internal AC_Artifact
-d_call_stack_artifact_create(String8 key, B32 *cancel_signal, B32 *retry_out, U64 *gen_out)
+d_call_stack_artifact_create(String8 key, B32 *cancel_signal, AC_Status *status_out, U64 *gen_out)
 {
   AC_Artifact artifact = {0};
   {
@@ -6168,14 +6173,19 @@ d_call_stack_artifact_create(String8 key, B32 *cancel_signal, B32 *retry_out, U6
         pre_reg_gen = d_reg_gen();
         pre_mem_gen = d_mem_gen();
         unwind = d_unwind_from_thread(arena, thread_handle, now_time_us()+100);
-        if(!(unwind.flags & D_UnwindFlag_Stale))
+        if(unwind.flags & D_UnwindFlag_Stale)
         {
-          good = 1;
-          call_stack[0] = d_call_stack_from_unwind(arena, process, &unwind);
+          retry = 1;
+        }
+        else if(unwind.flags & D_UnwindFlag_Error)
+        {
+          good = 0;
+          retry = 0;
         }
         else
         {
-          retry = 1;
+          good = 1;
+          call_stack[0] = d_call_stack_from_unwind(arena, process, &unwind);
         }
         post_reg_gen = d_reg_gen();
         post_mem_gen = d_mem_gen();
@@ -6204,8 +6214,19 @@ d_call_stack_artifact_create(String8 key, B32 *cancel_signal, B32 *retry_out, U6
       artifact.u64[1] = (U64)call_stack;
     }
     
-    //- rjf: mark retry
-    retry_out[0] = retry;
+    //- rjf: mark status
+    if(retry)
+    {
+      status_out[0] = AC_Status_NeedRetry;
+    }
+    else if(good)
+    {
+      status_out[0] = AC_Status_Good;
+    }
+    else
+    {
+      status_out[0] = AC_Status_Failed;
+    }
     
     scratch_end(scratch);
   }
@@ -6243,7 +6264,7 @@ d_call_stack_from_thread(Access *access, D_Handle thread_handle, B32 high_priori
 //~ rjf: Call Stack Tree Artifact Cache Hooks / Lookups
 
 internal AC_Artifact
-d_call_stack_tree_artifact_create(String8 key, B32 *cancel_signal, B32 *retry_out, U64 *gen_out)
+d_call_stack_tree_artifact_create(String8 key, B32 *cancel_signal, AC_Status *status_out, U64 *gen_out)
 {
   Temp scratch = scratch_begin(0, 0);
   Access *access = access_open();
@@ -6354,7 +6375,7 @@ d_call_stack_tree_artifact_create(String8 key, B32 *cancel_signal, B32 *retry_ou
   //- rjf: retry on stale
   if(stale)
   {
-    retry_out[0] = 1;
+    status_out[0] = AC_Status_NeedRetry;
   }
   
   access_close(access);

src/dbg_engine/dbg_engine_ctrl.h

@@ -640,7 +640,7 @@ internal String8 d_data_from_process_vaddr_range(Arena *arena, D_Handle process,
 #define d_process_write_struct(process, vaddr, ptr) d_process_write((process), r1u64((vaddr), (vaddr)+(sizeof(*ptr))), (ptr))
 
 //- rjf: process memory artifact cache
-internal AC_Artifact d_memory_artifact_create(String8 key, B32 *cancel_signal, B32 *retry_out, U64 *gen_out);
+internal AC_Artifact d_memory_artifact_create(String8 key, B32 *cancel_signal, AC_Status *status_out, U64 *gen_out);
 internal void d_memory_artifact_destroy(AC_Artifact artifact);
 internal C_Key d_key_from_process_vaddr_range(D_Handle process, Rng1U64 vaddr_range, B32 zero_terminated, B32 wait_for_fresh, U64 endt_us, B32 *out_is_stale);
 
@@ -652,21 +652,20 @@ internal B32 d_process_memory_read(D_Handle process, Rng1U64 range, B32 *is_stal
 ////////////////////////////////
 //~ rjf: TLS Address Artifact Cache Hooks / Lookups
 
-internal AC_Artifact d_tls_vaddr_artifact_create(String8 key, B32 *cancel_signal, B32 *retry_out, U64 *gen_out);
-internal void d_tls_vaddr_artifact_destroy(AC_Artifact artifact);
+internal AC_Artifact d_tls_vaddr_artifact_create(String8 key, B32 *cancel_signal, AC_Status *status_out, U64 *gen_out);
 internal U64 d_cached_tls_vaddr_from_thread_module(D_Handle thread_handle, D_Handle module_handle, U64 endt_us, B32 *stale_out);
 
 ////////////////////////////////
 //~ rjf: Call Stack Artifact Cache Hooks / Lookups
 
-internal AC_Artifact d_call_stack_artifact_create(String8 key, B32 *cancel_signal, B32 *retry_out, U64 *gen_out);
+internal AC_Artifact d_call_stack_artifact_create(String8 key, B32 *cancel_signal, AC_Status *status_out, U64 *gen_out);
 internal void d_call_stack_artifact_destroy(AC_Artifact artifact);
 internal D_CallStack d_call_stack_from_thread(Access *access, D_Handle thread_handle, B32 high_priority, U64 endt_us);
 
 ////////////////////////////////
 //~ rjf: Call Stack Tree Artifact Cache Hooks / Lookups
 
-internal AC_Artifact d_call_stack_tree_artifact_create(String8 key, B32 *cancel_signal, B32 *retry_out, U64 *gen_out);
+internal AC_Artifact d_call_stack_tree_artifact_create(String8 key, B32 *cancel_signal, AC_Status *status_out, U64 *gen_out);
 internal void d_call_stack_tree_artifact_destroy(AC_Artifact artifact);
 internal D_CallStackTree d_call_stack_tree(Access *access, U64 endt_us);