[PATCH v4 23/34] Pre-read DWARF section data

[Tom Tromey <tom@tromey.com>]

Because BFD is not thread-safe, we need to be sure that any section
data that is needed is read before trying to do any DWARF indexing in
the background.

This patch takes a simple approach to this -- it pre-reads the
"info"-related sections.  This is done for the main file, but also any
auxiliary files as well, such as the DWO file.

This patch could be perhaps enhanced by removing some now-redundant
calls to dwarf2_section_info::read.
---
 gdb/dwarf2/read.c | 221 +++++++++++++++++++++-------------------------
 gdb/dwarf2/read.h |   4 +
 2 files changed, 103 insertions(+), 122 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index c329ba5057b..094aa21303e 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -2039,6 +2039,25 @@ dwarf2_get_section_info (struct objfile *objfile,
   *sizep = info->size;
 }
 
+/* See dwarf2/read.h.  */
+
+void
+dwarf2_per_bfd::map_info_sections (struct objfile *objfile)
+{
+  info.read (objfile);
+  abbrev.read (objfile);
+  line.read (objfile);
+  str.read (objfile);
+  str_offsets.read (objfile);
+  line_str.read (objfile);
+  ranges.read (objfile);
+  rnglists.read (objfile);
+  addr.read (objfile);
+
+  for (auto &section : types)
+    section.read (objfile);
+}
+
 \f
 /* DWARF quick_symbol_functions support.  */
 
@@ -7831,7 +7850,7 @@ dwarf2_build_psymtabs_hard (dwarf2_per_objfile *per_objfile)
   scoped_restore restore_reading_psyms
     = make_scoped_restore (&per_bfd->reading_partial_symbols, true);
 
-  per_bfd->info.read (objfile);
+  per_bfd->map_info_sections (objfile);
 
   /* Any cached compilation units will be linked by the per-objfile
      read_in_chain.  Make sure to free them when we're done.  */
@@ -8018,8 +8037,16 @@ create_all_comp_units (dwarf2_per_objfile *per_objfile)
 
   dwz_file *dwz = dwarf2_get_dwz_file (per_objfile->per_bfd);
   if (dwz != NULL)
-    read_comp_units_from_section (per_objfile, &dwz->info, &dwz->abbrev, 1,
-				  types_htab, rcuh_kind::COMPILE);
+    {
+      /* Pre-read the sections we'll need to construct an index.  */
+      struct objfile *objfile = per_objfile->objfile;
+      dwz->abbrev.read (objfile);
+      dwz->info.read (objfile);
+      dwz->str.read (objfile);
+      dwz->line.read (objfile);
+      read_comp_units_from_section (per_objfile, &dwz->info, &dwz->abbrev, 1,
+				    types_htab, rcuh_kind::COMPILE);
+    }
 
   per_objfile->per_bfd->signatured_types = std::move (types_htab);
 }
@@ -12635,69 +12662,47 @@ open_dwo_file (dwarf2_per_objfile *per_objfile,
    size of each of the DWO debugging sections we are interested in.  */
 
 static void
-dwarf2_locate_dwo_sections (bfd *abfd, asection *sectp,
-			    dwo_sections *dwo_sections)
+dwarf2_locate_dwo_sections (struct objfile *objfile, bfd *abfd,
+			    asection *sectp, dwo_sections *dwo_sections)
 {
   const struct dwop_section_names *names = &dwop_section_names;
 
+  struct dwarf2_section_info *dw_sect = nullptr;
+
   if (names->abbrev_dwo.matches (sectp->name))
-    {
-      dwo_sections->abbrev.s.section = sectp;
-      dwo_sections->abbrev.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwo_sections->abbrev;
   else if (names->info_dwo.matches (sectp->name))
-    {
-      dwo_sections->info.s.section = sectp;
-      dwo_sections->info.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwo_sections->info;
   else if (names->line_dwo.matches (sectp->name))
-    {
-      dwo_sections->line.s.section = sectp;
-      dwo_sections->line.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwo_sections->line;
   else if (names->loc_dwo.matches (sectp->name))
-    {
-      dwo_sections->loc.s.section = sectp;
-      dwo_sections->loc.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwo_sections->loc;
   else if (names->loclists_dwo.matches (sectp->name))
-    {
-      dwo_sections->loclists.s.section = sectp;
-      dwo_sections->loclists.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwo_sections->loclists;
   else if (names->macinfo_dwo.matches (sectp->name))
-    {
-      dwo_sections->macinfo.s.section = sectp;
-      dwo_sections->macinfo.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwo_sections->macinfo;
   else if (names->macro_dwo.matches (sectp->name))
-    {
-      dwo_sections->macro.s.section = sectp;
-      dwo_sections->macro.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwo_sections->macro;
   else if (names->rnglists_dwo.matches (sectp->name))
-    {
-      dwo_sections->rnglists.s.section = sectp;
-      dwo_sections->rnglists.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwo_sections->rnglists;
   else if (names->str_dwo.matches (sectp->name))
-    {
-      dwo_sections->str.s.section = sectp;
-      dwo_sections->str.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwo_sections->str;
   else if (names->str_offsets_dwo.matches (sectp->name))
-    {
-      dwo_sections->str_offsets.s.section = sectp;
-      dwo_sections->str_offsets.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwo_sections->str_offsets;
   else if (names->types_dwo.matches (sectp->name))
     {
       struct dwarf2_section_info type_section;
 
       memset (&type_section, 0, sizeof (type_section));
-      type_section.s.section = sectp;
-      type_section.size = bfd_section_size (sectp);
       dwo_sections->types.push_back (type_section);
+      dw_sect = &dwo_sections->types.back ();
+    }
+
+  if (dw_sect != nullptr)
+    {
+      dw_sect->s.section = sectp;
+      dw_sect->size = bfd_section_size (sectp);
+      dw_sect->read (objfile);
     }
 }
 
@@ -12725,8 +12730,8 @@ open_and_init_dwo_file (dwarf2_cu *cu, const char *dwo_name,
   dwo_file->dbfd = std::move (dbfd);
 
   for (asection *sec : gdb_bfd_sections (dwo_file->dbfd))
-    dwarf2_locate_dwo_sections (dwo_file->dbfd.get (), sec,
-				&dwo_file->sections);
+    dwarf2_locate_dwo_sections (per_objfile->objfile, dwo_file->dbfd.get (),
+				sec, &dwo_file->sections);
 
   create_cus_hash_table (per_objfile, cu, *dwo_file, dwo_file->sections.info,
 			 dwo_file->cus);
@@ -12753,8 +12758,8 @@ open_and_init_dwo_file (dwarf2_cu *cu, const char *dwo_name,
    we are interested in.  */
 
 static void
-dwarf2_locate_common_dwp_sections (bfd *abfd, asection *sectp,
-				   dwp_file *dwp_file)
+dwarf2_locate_common_dwp_sections (struct objfile *objfile, bfd *abfd,
+				   asection *sectp, dwp_file *dwp_file)
 {
   const struct dwop_section_names *names = &dwop_section_names;
   unsigned int elf_section_nr = elf_section_data (sectp)->this_idx;
@@ -12765,20 +12770,19 @@ dwarf2_locate_common_dwp_sections (bfd *abfd, asection *sectp,
   dwp_file->elf_sections[elf_section_nr] = sectp;
 
   /* Look for specific sections that we need.  */
+  struct dwarf2_section_info *dw_sect = nullptr;
   if (names->str_dwo.matches (sectp->name))
-    {
-      dwp_file->sections.str.s.section = sectp;
-      dwp_file->sections.str.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.str;
   else if (names->cu_index.matches (sectp->name))
-    {
-      dwp_file->sections.cu_index.s.section = sectp;
-      dwp_file->sections.cu_index.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.cu_index;
   else if (names->tu_index.matches (sectp->name))
+    dw_sect = &dwp_file->sections.tu_index;
+
+  if (dw_sect != nullptr)
     {
-      dwp_file->sections.tu_index.s.section = sectp;
-      dwp_file->sections.tu_index.size = bfd_section_size (sectp);
+      dw_sect->s.section = sectp;
+      dw_sect->size = bfd_section_size (sectp);
+      dw_sect->read (objfile);
     }
 }
 
@@ -12788,7 +12792,8 @@ dwarf2_locate_common_dwp_sections (bfd *abfd, asection *sectp,
    have version 1 or 2 or 5 until we parse the cu_index/tu_index sections.  */
 
 static void
-dwarf2_locate_v2_dwp_sections (bfd *abfd, asection *sectp, void *dwp_file_ptr)
+dwarf2_locate_v2_dwp_sections (struct objfile *objfile, bfd *abfd,
+			       asection *sectp, void *dwp_file_ptr)
 {
   struct dwp_file *dwp_file = (struct dwp_file *) dwp_file_ptr;
   const struct dwop_section_names *names = &dwop_section_names;
@@ -12800,45 +12805,29 @@ dwarf2_locate_v2_dwp_sections (bfd *abfd, asection *sectp, void *dwp_file_ptr)
   dwp_file->elf_sections[elf_section_nr] = sectp;
 
   /* Look for specific sections that we need.  */
+  struct dwarf2_section_info *dw_sect = nullptr;
   if (names->abbrev_dwo.matches (sectp->name))
-    {
-      dwp_file->sections.abbrev.s.section = sectp;
-      dwp_file->sections.abbrev.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.abbrev;
   else if (names->info_dwo.matches (sectp->name))
-    {
-      dwp_file->sections.info.s.section = sectp;
-      dwp_file->sections.info.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.info;
   else if (names->line_dwo.matches (sectp->name))
-    {
-      dwp_file->sections.line.s.section = sectp;
-      dwp_file->sections.line.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.line;
   else if (names->loc_dwo.matches (sectp->name))
-    {
-      dwp_file->sections.loc.s.section = sectp;
-      dwp_file->sections.loc.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.loc;
   else if (names->macinfo_dwo.matches (sectp->name))
-    {
-      dwp_file->sections.macinfo.s.section = sectp;
-      dwp_file->sections.macinfo.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.macinfo;
   else if (names->macro_dwo.matches (sectp->name))
-    {
-      dwp_file->sections.macro.s.section = sectp;
-      dwp_file->sections.macro.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.macro;
   else if (names->str_offsets_dwo.matches (sectp->name))
-    {
-      dwp_file->sections.str_offsets.s.section = sectp;
-      dwp_file->sections.str_offsets.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.str_offsets;
   else if (names->types_dwo.matches (sectp->name))
+    dw_sect = &dwp_file->sections.types;
+
+  if (dw_sect != nullptr)
     {
-      dwp_file->sections.types.s.section = sectp;
-      dwp_file->sections.types.size = bfd_section_size (sectp);
+      dw_sect->s.section = sectp;
+      dw_sect->size = bfd_section_size (sectp);
+      dw_sect->read (objfile);
     }
 }
 
@@ -12848,7 +12837,8 @@ dwarf2_locate_v2_dwp_sections (bfd *abfd, asection *sectp, void *dwp_file_ptr)
    have version 1 or 2 or 5 until we parse the cu_index/tu_index sections.  */
 
 static void
-dwarf2_locate_v5_dwp_sections (bfd *abfd, asection *sectp, void *dwp_file_ptr)
+dwarf2_locate_v5_dwp_sections (struct objfile *objfile, bfd *abfd,
+			       asection *sectp, void *dwp_file_ptr)
 {
   struct dwp_file *dwp_file = (struct dwp_file *) dwp_file_ptr;
   const struct dwop_section_names *names = &dwop_section_names;
@@ -12860,40 +12850,27 @@ dwarf2_locate_v5_dwp_sections (bfd *abfd, asection *sectp, void *dwp_file_ptr)
   dwp_file->elf_sections[elf_section_nr] = sectp;
 
   /* Look for specific sections that we need.  */
+  struct dwarf2_section_info *dw_sect = nullptr;
   if (names->abbrev_dwo.matches (sectp->name))
-    {
-      dwp_file->sections.abbrev.s.section = sectp;
-      dwp_file->sections.abbrev.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.abbrev;
   else if (names->info_dwo.matches (sectp->name))
-    {
-      dwp_file->sections.info.s.section = sectp;
-      dwp_file->sections.info.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.info;
   else if (names->line_dwo.matches (sectp->name))
-   {
-     dwp_file->sections.line.s.section = sectp;
-     dwp_file->sections.line.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.line;
   else if (names->loclists_dwo.matches (sectp->name))
-    {
-      dwp_file->sections.loclists.s.section = sectp;
-      dwp_file->sections.loclists.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.loclists;
   else if (names->macro_dwo.matches (sectp->name))
-    {
-      dwp_file->sections.macro.s.section = sectp;
-      dwp_file->sections.macro.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.macro;
   else if (names->rnglists_dwo.matches (sectp->name))
-    {
-      dwp_file->sections.rnglists.s.section = sectp;
-      dwp_file->sections.rnglists.size = bfd_section_size (sectp);
-    }
+    dw_sect = &dwp_file->sections.rnglists;
   else if (names->str_offsets_dwo.matches (sectp->name))
+    dw_sect = &dwp_file->sections.str_offsets;
+
+  if (dw_sect != nullptr)
     {
-      dwp_file->sections.str_offsets.s.section = sectp;
-      dwp_file->sections.str_offsets.size = bfd_section_size (sectp);
+      dw_sect->s.section = sectp;
+      dw_sect->size = bfd_section_size (sectp);
+      dw_sect->read (objfile);
     }
 }
 
@@ -13020,7 +12997,7 @@ open_and_init_dwp_file (dwarf2_per_objfile *per_objfile)
 		    dwp_file->num_sections, asection *);
 
   for (asection *sec : gdb_bfd_sections (dwp_file->dbfd))
-    dwarf2_locate_common_dwp_sections (dwp_file->dbfd.get (), sec,
+    dwarf2_locate_common_dwp_sections (objfile, dwp_file->dbfd.get (), sec,
 				       dwp_file.get ());
 
   dwp_file->cus = create_dwp_hash_table (per_objfile, dwp_file.get (), 0);
@@ -13050,10 +13027,10 @@ open_and_init_dwp_file (dwarf2_per_objfile *per_objfile)
   for (asection *sec : gdb_bfd_sections (dwp_file->dbfd))
     {
       if (dwp_file->version == 2)
-	dwarf2_locate_v2_dwp_sections (dwp_file->dbfd.get (), sec,
+	dwarf2_locate_v2_dwp_sections (objfile, dwp_file->dbfd.get (), sec,
 				       dwp_file.get ());
       else
-	dwarf2_locate_v5_dwp_sections (dwp_file->dbfd.get (), sec,
+	dwarf2_locate_v5_dwp_sections (objfile, dwp_file->dbfd.get (), sec,
 				       dwp_file.get ());
     }
 
diff --git a/gdb/dwarf2/read.h b/gdb/dwarf2/read.h
index 4158a06e2bc..4ee7de98c50 100644
--- a/gdb/dwarf2/read.h
+++ b/gdb/dwarf2/read.h
@@ -368,6 +368,10 @@ struct dwarf2_per_bfd
      is allocated on the dwarf2_per_bfd obstack.  */
   signatured_type_up allocate_signatured_type (ULONGEST signature);
 
+  /* Map all the DWARF section data needed when scanning
+     .debug_info.  */
+  void map_info_sections (struct objfile *objfile);
+
 private:
   /* This function is mapped across the sections and remembers the
      offset and size of each of the debugging sections we are
-- 
2.34.1