Bug 1023461 - Record filename and line number for chrome JS entries; r=snorp

xpcom/threads/ThreadStackHelper.cpp

@@ -8,10 +8,15 @@
 #include "nsJSPrincipals.h"
 #include "nsScriptSecurityManager.h"
 #include "jsfriendapi.h"
+#include "prprf.h"
+
+#include "js/OldDebugAPI.h"
 
 #include "mozilla/Assertions.h"
 #include "mozilla/Move.h"
 
+#include <string.h>
+
 #ifdef XP_LINUX
 #include <unistd.h>
 #include <sys/syscall.h>
@@ -59,6 +64,7 @@ ThreadStackHelper::ThreadStackHelper()
 #endif
     mStackToFill(nullptr)
   , mMaxStackSize(Stack::sMaxInlineStorage)
+  , mMaxBufferSize(0)
 {
 #if defined(XP_LINUX)
   mThreadID = ::syscall(SYS_gettid);
@@ -202,7 +208,11 @@ ThreadStackHelper::PrepareStackBuffer(Stack& aStack)
   }
 #endif
   MOZ_ASSERT(mPseudoStack);
-  MOZ_ALWAYS_TRUE(aStack.reserve(mMaxStackSize));
+  if (!aStack.reserve(mMaxStackSize) ||
+      !aStack.reserve(aStack.capacity()) || // reserve up to the capacity
+      !aStack.EnsureBufferCapacity(mMaxBufferSize)) {
+    return false;
+  }
   mStackToFill = &aStack;
   return true;
 #else
@@ -232,21 +242,46 @@ IsChromeJSScript(JSScript* aScript)
 
 const char*
 ThreadStackHelper::AppendJSEntry(const volatile StackEntry* aEntry,
+                                 intptr_t& aAvailableBufferSize,
                                  const char* aPrevLabel)
 {
   // May be called from another thread or inside a signal handler.
   // We assume querying the script is safe but we must not manupulate it.
+  // Also we must not allocate any memory from heap.
   MOZ_ASSERT(aEntry->isJs());
   MOZ_ASSERT(aEntry->script());
 
   const char* label;
   if (IsChromeJSScript(aEntry->script())) {
+    const char* const filename = JS_GetScriptFilename(aEntry->script());
+    unsigned lineno = JS_PCToLineNumber(nullptr, aEntry->script(),
+                                        aEntry->pc());
+    MOZ_ASSERT(filename);
+
+    char buffer[64]; // Enough to fit longest js file name from the tree
+    const char* const basename = strrchr(filename, '/');
+    size_t len = PR_snprintf(buffer, sizeof(buffer), "%s:%u",
+                             basename ? basename + 1 : filename, lineno);
+    if (len < sizeof(buffer)) {
+      if (mStackToFill->IsSameAsEntry(aPrevLabel, buffer)) {
+        return aPrevLabel;
+      }
+
+      // Keep track of the required buffer size
+      aAvailableBufferSize -= (len + 1);
+      if (aAvailableBufferSize >= 0) {
+        // Buffer is big enough.
+        return mStackToFill->InfallibleAppendViaBuffer(buffer, len);
+      }
+      // Buffer is not big enough; fall through to using static label below.
+    }
+    // snprintf failed or buffer is not big enough.
     label = "(chrome script)";
   } else {
     label = "(content script)";
   }
 
-  if (label == aPrevLabel) {
+  if (mStackToFill->IsSameAsEntry(aPrevLabel, label)) {
     return aPrevLabel;
   }
   mStackToFill->infallibleAppend(label);
@@ -258,8 +293,12 @@ ThreadStackHelper::AppendJSEntry(const volatile StackEntry* aEntry,
 void
 ThreadStackHelper::FillStackBuffer()
 {
+  MOZ_ASSERT(mStackToFill->empty());
+
 #ifdef MOZ_ENABLE_PROFILER_SPS
-  size_t reservedSize = mMaxStackSize;
+  size_t reservedSize = mStackToFill->capacity();
+  size_t reservedBufferSize = mStackToFill->AvailableBufferSize();
+  intptr_t availableBufferSize = intptr_t(reservedBufferSize);
 
   // Go from front to back
   const volatile StackEntry* entry = mPseudoStack->mStack;
@@ -267,24 +306,32 @@ ThreadStackHelper::FillStackBuffer()
   // Deduplicate identical, consecutive frames
   const char* prevLabel = nullptr;
   for (; reservedSize-- && entry != end; entry++) {
-    /* We only accept non-copy labels, because
-       we are unable to actually copy labels here */
+    /* We only accept non-copy labels, including js::RunScript,
+       because we only want static labels in the hang stack. */
     if (entry->isCopyLabel()) {
       continue;
     }
     if (entry->isJs()) {
-      prevLabel = AppendJSEntry(entry, prevLabel);
+      prevLabel = AppendJSEntry(entry, availableBufferSize, prevLabel);
       continue;
     }
     const char* const label = entry->label();
-    if (label == prevLabel) {
+    if (mStackToFill->IsSameAsEntry(prevLabel, label)) {
       continue;
     }
     mStackToFill->infallibleAppend(label);
     prevLabel = label;
   }
-  // If we exited early due to buffer size, expand the buffer for next time
-  mMaxStackSize += (end - entry);
+
+  // end != entry if we exited early due to not enough reserved frames.
+  // Expand the number of reserved frames for next time.
+  mMaxStackSize = mStackToFill->capacity() + (end - entry);
+
+  // availableBufferSize < 0 if we needed a larger buffer than we reserved.
+  // Calculate a new reserve size for next time.
+  if (availableBufferSize < 0) {
+    mMaxBufferSize = reservedBufferSize - availableBufferSize;
+  }
 #endif
 }