gdb/dwarf: look up .dwp file ahead of time

get_dwp_file lazily looks for a .dwp file for the given objfile.  It is
called by indexing workers, when a cutu_reader object looks for a DWO
file.  It is called with the "dwo_lock" held, meaning that the first
worker to get there will do the work, while the others will wait at the
lock.

I'm trying to reduce the time where this lock is taken and do other
refactorings to make it easier to reason about the DWARF reader code.
Moving the lookup of the .dwp file ahead, before we start parallelizing
work, helps makes things simpler, because we can then assume everywhere
else that we have already checked for a .dwp file.

Put the call to open_and_init_dwp_file in dwarf2_has_info, right next to
where we look up .dwz files.  I used the same try-catch pattern as for
the .dwz file lookup.

Change-Id: I615da85f62a66d752607f0dbe9f0372dfa04b86b
Approved-By: Tom Tromey <tom@tromey.com>

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 21cfa026d432ad9669c6720c0c9f2533a344801e..659c9520056c6f0638013fc80de792ddf4dde968 100644 (file)
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -1039,7 +1039,7 @@ static struct dwo_unit *lookup_dwo_unit_in_dwp
   (dwarf2_per_bfd *per_bfd, struct dwp_file *dwp_file,
    const char *comp_dir, ULONGEST signature, int is_debug_types);
 
-static struct dwp_file *get_dwp_file (dwarf2_per_objfile *per_objfile);
+static void open_and_init_dwp_file (dwarf2_per_objfile *per_objfile);
 
 static struct dwo_unit *lookup_dwo_comp_unit
   (dwarf2_cu *cu, const char *dwo_name, const char *comp_dir,
@@ -1295,6 +1295,15 @@ dwarf2_has_info (struct objfile *objfile,
        {
          warning (_("%s"), err.what ());
        }
+
+      try
+       {
+         open_and_init_dwp_file (per_objfile);
+       }
+      catch (const gdb_exception_error &err)
+       {
+         warning (_("%s"), err.what ());
+       }
     }
 
   return has_info;
@@ -1632,7 +1641,7 @@ dw2_do_instantiate_symtab (dwarf2_per_cu *per_cu,
            && per_objfile->per_bfd->index_table != NULL
            && !per_objfile->per_bfd->index_table->version_check ()
            /* DWP files aren't supported yet.  */
-           && get_dwp_file (per_objfile) == NULL)
+           && per_objfile->per_bfd->dwp_file == nullptr)
          queue_and_load_all_dwo_tus (cu);
       }
 
@@ -2607,7 +2616,7 @@ lookup_dwp_signatured_type (struct dwarf2_cu *cu, ULONGEST sig)
 {
   dwarf2_per_objfile *per_objfile = cu->per_objfile;
   dwarf2_per_bfd *per_bfd = per_objfile->per_bfd;
-  struct dwp_file *dwp_file = get_dwp_file (per_objfile);
+  dwp_file *dwp_file = per_objfile->per_bfd->dwp_file.get ();
 
   gdb_assert (cu->dwo_unit);
   gdb_assert (dwp_file != NULL);
@@ -2649,7 +2658,7 @@ lookup_signatured_type (struct dwarf2_cu *cu, ULONGEST sig)
     {
       /* We're in a DWO/DWP file, and we're using .gdb_index.
         These cases require special processing.  */
-      if (get_dwp_file (per_objfile) == NULL)
+      if (per_objfile->per_bfd->dwp_file == nullptr)
        return lookup_dwo_signatured_type (cu, sig);
       else
        return lookup_dwp_signatured_type (cu, sig);
@@ -3506,7 +3515,7 @@ process_skeletonless_type_units (dwarf2_per_objfile *per_objfile,
                                 cooked_index_worker_result *storage)
 {
   /* Skeletonless TUs in DWP files without .gdb_index is not supported yet.  */
-  if (get_dwp_file (per_objfile) == nullptr)
+  if (per_objfile->per_bfd->dwp_file == nullptr)
     for (const dwo_file_up &file : per_objfile->per_bfd->dwo_files)
       for (dwo_unit *unit : file->tus)
        process_skeletonless_type_unit (unit, per_objfile, storage);
@@ -7796,10 +7805,9 @@ open_dwp_file (dwarf2_per_bfd *per_bfd, const char *file_name)
 }
 
 /* Initialize the use of the DWP file for the current objfile.
-   By convention the name of the DWP file is ${objfile}.dwp.
-   The result is NULL if it can't be found.  */
+   By convention the name of the DWP file is ${objfile}.dwp.  */
 
-static dwp_file_up
+static void
 open_and_init_dwp_file (dwarf2_per_objfile *per_objfile)
 {
   struct objfile *objfile = per_objfile->objfile;
@@ -7837,7 +7845,7 @@ open_and_init_dwp_file (dwarf2_per_objfile *per_objfile)
     {
       dwarf_read_debug_printf ("DWP file not found: %s", dwp_name.c_str ());
 
-      return dwp_file_up ();
+      return;
     }
 
   const char *name = bfd_get_filename (dbfd.get ());
@@ -7894,20 +7902,8 @@ open_and_init_dwp_file (dwarf2_per_objfile *per_objfile)
 
   bfd_cache_close (dwp_file->dbfd.get ());
 
-  return dwp_file;
-}
-
-/* Wrapper around open_and_init_dwp_file, only open it once.  */
-
-static struct dwp_file *
-get_dwp_file (dwarf2_per_objfile *per_objfile)
-{
-  if (!per_objfile->per_bfd->dwp_checked)
-    {
-      per_objfile->per_bfd->dwp_file = open_and_init_dwp_file (per_objfile);
-      per_objfile->per_bfd->dwp_checked = 1;
-    }
-  return per_objfile->per_bfd->dwp_file.get ();
+  /* Everything worked, install this dwp_file in the per_bfd.  */
+  per_objfile->per_bfd->dwp_file = std::move (dwp_file);
 }
 
 /* Subroutine of lookup_dwo_comp_unit, lookup_dwo_type_unit.
@@ -7934,14 +7930,14 @@ lookup_dwo_cutu (dwarf2_cu *cu, const char *dwo_name, const char *comp_dir,
   dwarf2_per_bfd *per_bfd = per_objfile->per_bfd;
   struct objfile *objfile = per_objfile->objfile;
   const char *kind = is_debug_types ? "TU" : "CU";
-  struct dwp_file *dwp_file;
 
   /* First see if there's a DWP file.
      If we have a DWP file but didn't find the DWO inside it, don't
      look for the original DWO file.  It makes gdb behave differently
      depending on whether one is debugging in the build tree.  */
 
-  dwp_file = get_dwp_file (per_objfile);
+  dwp_file *dwp_file = per_objfile->per_bfd->dwp_file.get ();
+
   if (dwp_file != NULL)
     {
       const struct dwp_hash_table *dwp_htab =
@@ -8098,7 +8094,7 @@ queue_and_load_all_dwo_tus (dwarf2_cu *cu)
 
   gdb_assert (cu != nullptr);
   gdb_assert (!cu->per_cu->is_debug_types);
-  gdb_assert (get_dwp_file (cu->per_objfile) == nullptr);
+  gdb_assert (cu->per_objfile->per_bfd->dwp_file == nullptr);
 
   dwo_unit = cu->dwo_unit;
   gdb_assert (dwo_unit != NULL);

diff --git a/gdb/dwarf2/read.h b/gdb/dwarf2/read.h
index 3177b19ede57fd23f7c3d1a8f76745d61c8e3352..a7f39fb77154fe616d324a8539da50b6e0f03733 100644 (file)
--- a/gdb/dwarf2/read.h
+++ b/gdb/dwarf2/read.h
@@ -634,9 +634,6 @@ public:
   /* Set of dwo_file objects.  */
   dwo_file_up_set dwo_files;
 
-  /* True if we've checked for whether there is a DWP file.  */
-  bool dwp_checked = false;
-
   /* The DWP file if there is one, or NULL.  */
   dwp_file_up dwp_file;