[gold commit] PR gold/14860: Fix race condition.

[ccoutant at google dot com (Cary Coutant)]

This patch fixes a race condition in Eh_frame_hdr::record_fde. When
running multi-threaded, many Write_sections tasks may call record_fde_,
which pushes an entry onto a shared vector. We need to hold a lock
while modifying the vector.

-cary


2013-11-14  Cary Coutant  <ccoutant@google.com>

gold/
	PR gold/14860
	* ehframe.cc (Eh_frame_hdr::Eh_frame_hdr): Initialize lock_.
	(Ehframe_hdr::set_final_data_size): Allocate a Lock.
	* ehframe.h (Eh_frame_hdr::record_fde): Hold the lock while
	updating fde_offsets_.
	(Eh_frame_hdr::lock_): New data member.


commit b8b27651e665a28de137c1dcfca501b41424788d
Author: Cary Coutant <ccoutant@google.com>
Date:   Fri Oct 11 14:12:16 2013 -0700

    Fix race condition in Eh_frame_hdr.

diff --git a/gold/ehframe.cc b/gold/ehframe.cc
index 08a9ec6..be262bf 100644
--- a/gold/ehframe.cc
+++ b/gold/ehframe.cc
@@ -84,7 +84,8 @@ Eh_frame_hdr::Eh_frame_hdr(Output_section* eh_frame_section,
     eh_frame_section_(eh_frame_section),
     eh_frame_data_(eh_frame_data),
     fde_offsets_(),
-    any_unrecognized_eh_frame_sections_(false)
+    any_unrecognized_eh_frame_sections_(false),
+    lock_(NULL)
 {
 }
 
@@ -102,6 +103,9 @@ Eh_frame_hdr::set_final_data_size()
       this->fde_offsets_.reserve(fde_count);
     }
   this->set_data_size(data_size);
+  // We need a lock for updating the fde_offsets_ vector while writing
+  // the FDEs.
+  this->lock_ = new Lock();
 }
 
 // Write the data to the file.
diff --git a/gold/ehframe.h b/gold/ehframe.h
index 8aab8b8..d5ac668 100644
--- a/gold/ehframe.h
+++ b/gold/ehframe.h
@@ -60,7 +60,10 @@ class Eh_frame_hdr : public Output_section_data
   record_fde(section_offset_type fde_offset, unsigned char fde_encoding)
   {
     if (!this->any_unrecognized_eh_frame_sections_)
-      this->fde_offsets_.push_back(std::make_pair(fde_offset, fde_encoding));
+      {
+	Hold_lock(*this->lock_);
+	this->fde_offsets_.push_back(std::make_pair(fde_offset, fde_encoding));
+      }
   }
 
  protected:
@@ -157,6 +160,8 @@ class Eh_frame_hdr : public Output_section_data
   // Whether we found any .eh_frame sections which we could not
   // process.
   bool any_unrecognized_eh_frame_sections_;
+  // Lock held while updating fde_offsets_.
+  Lock* lock_;
 };
 
 // This class holds an FDE.