PR11246: Add more granular cache control

There are some module options that require us to disable caching for the
script, but before now this had a global effect.  There are some cache
objects, like tracepoint and @cast query modules, which we would like to
cache even when the script itself needs to be uncached.

* session.h (systemtap_session): New use_script_cache flag.
* main.cxx (main): -m & -k can just disable the script cache.  Failure to
  create the cache directories still disables all caching.
* hash.cxx (create_hashdir): Failure disables all caching.
* cache.cxx (add_to_cache): Failure only toggles the script caching. If
  the stapconf fails though, we don't need to block the .ko reuse.

4 files changed, 17 insertions, 12 deletions

diff --git a/cache.cxx b/cache.cxx
index b113e019..1b083d69 100644
--- a/cache.cxx
+++ b/cache.cxx
@@ -57,15 +57,18 @@ add_to_cache(systemtap_session& s)
   string stapconf_src_path = s.tmpdir + "/" + s.stapconf_name;
   if (!copy_file(stapconf_src_path, s.stapconf_path, verbose))
     {
-      s.use_cache = false;
-      return;
+      // NB: this is not so severe as to prevent reuse of the .ko
+      // already copied.
+      //
+      // s.use_script_cache = false;
+      // return;
     }
 
   string module_src_path = s.tmpdir + "/" + s.module_name + ".ko";
   STAP_PROBE2(stap, cache__add__module, module_src_path.c_str(), s.hash_path.c_str());
   if (!copy_file(module_src_path, s.hash_path, verbose))
     {
-      s.use_cache = false;
+      s.use_script_cache = false;
       return;
     }
   // Copy the signature file, if any. It is not an error if this fails.
@@ -83,7 +86,7 @@ add_to_cache(systemtap_session& s)
       // NB: this is not so severe as to prevent reuse of the .ko
       // already copied.
       //
-      // s.use_cache = false;
+      // s.use_script_cache = false;
     }
 }
 
diff --git a/hash.cxx b/hash.cxx
index 1ebc76e5..36a71a42 100644
--- a/hash.cxx
+++ b/hash.cxx
@@ -170,7 +170,7 @@ create_hashdir (systemtap_session& s, const string& result, string& hashdir)
             cerr << "Warning: failed to create cache directory (\""
                  << hashdir + "\"): " << strerror(errno)
                  << ", disabling cache support." << endl;
-	  s.use_cache = false;
+	  s.use_cache = s.use_script_cache = false;
 	  return false;
 	}
     }
diff --git a/main.cxx b/main.cxx
index 21a4b136..5255b5bf 100644
--- a/main.cxx
+++ b/main.cxx
@@ -536,6 +536,7 @@ main (int argc, char * const argv [])
   s.perfmon=0;
   s.symtab = false;
   s.use_cache = true;
+  s.use_script_cache = true;
   s.tapset_compile_coverage = false;
   s.need_uprobes = false;
   s.consult_symtab = false;
@@ -584,7 +585,7 @@ main (int argc, char * const argv [])
         cerr << "Warning: failed to create systemtap data directory (\""
              << s.data_path << "\"): " << e
              << ", disabling cache support." << endl;
-      s.use_cache = false;
+      s.use_cache = s.use_script_cache = false;
     }
 
   if (s.use_cache)
@@ -597,7 +598,7 @@ main (int argc, char * const argv [])
             cerr << "Warning: failed to create cache directory (\""
                  << s.cache_path << "\"): " << e
                  << ", disabling cache support." << endl;
-	  s.use_cache = false;
+	  s.use_cache = s.use_script_cache = false;
 	}
     }
 
@@ -781,7 +782,7 @@ main (int argc, char * const argv [])
 	      }
 	  }
 
-	  s.use_cache = false;
+	  s.use_script_cache = false;
           break;
 
         case 'r':
@@ -797,7 +798,7 @@ main (int argc, char * const argv [])
 
         case 'k':
           s.keep_tmpdir = true;
-          s.use_cache = false; /* User wants to keep a usable build tree. */
+          s.use_script_cache = false; /* User wants to keep a usable build tree. */
           break;
 
         case 'g':
@@ -1276,7 +1277,7 @@ main (int argc, char * const argv [])
          << endl;
   // Generate hash.  There isn't any point in generating the hash
   // if last_pass is 2, since we'll quit before using it.
-  else if (s.last_pass != 2 && s.use_cache)
+  else if (s.last_pass != 2 && s.use_script_cache)
     {
       ostringstream o;
       unsigned saved_verbose;
@@ -1374,12 +1375,12 @@ main (int argc, char * const argv [])
   else
     {
       // Update cache. Cache cleaning is kicked off at the beginning of this function.
-      if (s.use_cache)
+      if (s.use_script_cache)
         add_to_cache(s);
 
       // We may need to save the module in $CWD if the cache was
       // inaccessible for some reason.
-      if (! s.use_cache && s.last_pass == 4)
+      if (! s.use_script_cache && s.last_pass == 4)
         save_module = true;
 
       // Copy module to the current directory.
diff --git a/session.h b/session.h
index 18d811e7..f45f6c77 100644
--- a/session.h
+++ b/session.h
@@ -127,6 +127,7 @@ struct systemtap_session
 
   // Cache data
   bool use_cache;
+  bool use_script_cache;
   std::string cache_path;
   std::string hash_path;
   std::string stapconf_path;