[Lldb-commits] [PATCH] D131130: [lldb] Improve EXC_RESOURCE exception reason

[Jonas Devlieghere via Phabricator via lldb-commits]

JDevlieghere created this revision.
JDevlieghere added reviewers: jasonmolenda, jingham.
Herald added a project: All.
JDevlieghere requested review of this revision.

Jason noted that the stop message we print for a memory high water mark notification (EXC_RESOURCE) could be clearer. Currently, the stop message looks like this:

  * thread #3, queue = 'com.apple.CFNetwork.LoaderQ', stop reason = EXC_RESOURCE RESOURCE_TYPE_MEMORY (limit=14 MB, unused=0x0)
      frame #0: 0x00000001f6a8c09c dyld`dyld4::APIs::dyld_shared_cache_some_image_overridden()
  dyld`dyld4::APIs::dyld_shared_cache_some_image_overridden:
  ->  0x1f6a8c09c <+0>:  pacibsp
      0x1f6a8c0a0 <+4>:  sub    sp, sp, #0x30
      0x1f6a8c0a4 <+8>:  stp    x20, x19, [sp, #0x10]
      0x1f6a8c0a8 <+12>: stp    x29, x30, [sp, #0x20]

It's hard to read the message because the exception and the types (EXC_RESOURCE RESOURCE_TYPE_MEMORY) blend together. Additionally, the "observed=0x0" should not be printed for memory limit exceptions.

I wanted to continue to include the resource type from `<kern/exc_resource.h>` while also explaining what it actually is.  With this path, the stop reason now looks like this:

  * thread #5, stop reason = EXC_RESOURCE (RESOURCE_TYPE_MEMORY: high watermark memory limit exceeded) (limit=14 MB)
      frame #0: 0x000000022500bb90 libsystem_pthread.dylib`start_wqthread
  libsystem_pthread.dylib`start_wqthread:
  ->  0x22500bb90 <+0>: stp    xzr, xzr, [sp, #-0x10]!
      0x22500bb94 <+4>: bl     0x22500bcd8               ; _pthread_wqthread
      0x22500bb98 <+8>: brk    #0x1

rdar://40466897


https://reviews.llvm.org/D131130

Files:
  lldb/source/Plugins/Process/Utility/StopInfoMachException.cpp


Index: lldb/source/Plugins/Process/Utility/StopInfoMachException.cpp
===================================================================
--- lldb/source/Plugins/Process/Utility/StopInfoMachException.cpp
+++ lldb/source/Plugins/Process/Utility/StopInfoMachException.cpp
@@ -410,7 +410,7 @@
 
       switch (resource_type) {
       case RESOURCE_TYPE_CPU:
-        exc_desc = "EXC_RESOURCE RESOURCE_TYPE_CPU";
+        exc_desc = "EXC_RESOURCE (RESOURCE_TYPE_CPU: CPU usage monitor tripped)";
         snprintf(code_desc_buf, sizeof(code_desc_buf), "%d%%",
                  (int)EXC_RESOURCE_CPUMONITOR_DECODE_PERCENTAGE(m_exc_code));
         snprintf(subcode_desc_buf, sizeof(subcode_desc_buf), "%d%%",
@@ -418,7 +418,7 @@
                      m_exc_subcode));
         break;
       case RESOURCE_TYPE_WAKEUPS:
-        exc_desc = "EXC_RESOURCE RESOURCE_TYPE_WAKEUPS";
+        exc_desc = "EXC_RESOURCE (RESOURCE_TYPE_WAKEUPS: idle wakeups monitor tripped)";
         snprintf(
             code_desc_buf, sizeof(code_desc_buf), "%d w/s",
             (int)EXC_RESOURCE_CPUMONITOR_DECODE_WAKEUPS_PERMITTED(m_exc_code));
@@ -427,11 +427,11 @@
                      m_exc_subcode));
         break;
       case RESOURCE_TYPE_MEMORY:
-        exc_desc = "EXC_RESOURCE RESOURCE_TYPE_MEMORY";
+        exc_desc = "EXC_RESOURCE (RESOURCE_TYPE_MEMORY: high watermark memory limit exceeded)";
         snprintf(code_desc_buf, sizeof(code_desc_buf), "%d MB",
                  (int)EXC_RESOURCE_HWM_DECODE_LIMIT(m_exc_code));
         subcode_desc = nullptr;
-        subcode_label = "unused";
+        subcode_label = nullptr;
         break;
 #if defined(RESOURCE_TYPE_IO)
       // RESOURCE_TYPE_IO is introduced in macOS SDK 10.12.
@@ -470,7 +470,7 @@
   if (m_exc_data_count >= 2) {
     if (subcode_desc)
       strm.Printf(", %s=%s", subcode_label, subcode_desc);
-    else
+    else if (subcode_label)
       strm.Printf(", %s=0x%" PRIx64, subcode_label, m_exc_subcode);
   }
 


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