Allow runners to write into the instrumentation dir.

krun.py

@@ -284,6 +284,10 @@ def inner_main(mailer, on_first_invocation, config, args):
     platform.no_pstate_check = args.no_pstate_check
     platform.hardware_reboots = args.hardware_reboots
 
+    # Create the instrumentation directory if required
+    if on_first_invocation:
+        util.make_instr_dir(config)
+
     debug("Checking platform preliminaries")
     platform.check_preliminaries()
 

krun/util.py

@@ -42,6 +42,9 @@
 import shutil
 import sys
 import subprocess
+import pwd
+import grp
+import getpass
 from subprocess import Popen, PIPE
 from logging import error, debug, info, warn, root as root_logger
 from bz2 import BZ2File
@@ -60,6 +63,10 @@
 # than are strictly necessary. In either case we are safe and correct.
 PIPE_BUF_SZ = 1024 * 16
 
+from stat import S_IRUSR, S_IWUSR, S_IRGRP, S_IWGRP, S_IXUSR, S_IXGRP, S_IROTH, S_IXOTH
+INSTR_DIR_MODE = S_IRUSR | S_IWUSR | S_IXUSR \
+    | S_IRGRP | S_IWGRP | S_IXGRP \
+    | S_IROTH | S_IXOTH
 
 DIR = os.path.abspath(os.path.dirname(__file__))
 
@@ -439,15 +446,46 @@ def get_instr_json_dir(config):
     return os.path.join(os.getcwd(), "%s_instr_data" % config_base)
 
 
+def make_instr_dir(config):
+    # We only want make a dir if >=1 VM is in instrumentation mode.
+    for vm in config.VMS.itervalues():
+        if vm['vm_def'].instrument:
+            break
+    else:
+        return  # no VM is in instrumentation mode.
+
+    dir = get_instr_json_dir(config)
+    debug("making instrumentation dir: %s" % dir)
+    os.mkdir(dir)
+
+
+def set_instr_dir_perms(config, platform):
+    """Grant the Krun user write access to the instrumentation dir.
+
+    Sadly this has to be done as root as there is no guarantee that the initial
+    user is in the krun user's group."""
+
+    from krun.vm_defs import BENCHMARK_USER
+    group = grp.getgrnam(BENCHMARK_USER).gr_name
+    user = pwd.getpwnam(getpass.getuser()).pw_name
+
+    from krun import util
+    path = util.get_instr_json_dir(config)
+
+    args = platform.change_user_args()
+    args.extend(["chown", "%s:%s" % (user, group), path])
+    run_shell_cmd(" ".join(args))
+
+    os.chmod(path, INSTR_DIR_MODE)
+
+
 def dump_instr_json(key, exec_num, config, instr_data):
-    """Write per-execution instrumentation data to a separate JSON file"""
+    """Write per-execution instrumentation data to a separate JSON file.
 
-    instr_json_dir = get_instr_json_dir(config)
-    if not os.path.exists(instr_json_dir):
-        os.mkdir(instr_json_dir)
+    Assumes the instrumentation directory exists."""
 
     filename = "%s__%s.json.bz2" % (key.replace(":", "__"), exec_num)
-    path = os.path.join(instr_json_dir, filename)
+    path = os.path.join(get_instr_json_dir(config), filename)
 
     # The directory was checked to be non-existant when the benchmark session
     # started, so it follows that the instrumentation JSON file (each of which

krun/vm_defs.py

@@ -239,6 +239,10 @@ def _run_exec(self, args, heap_lim_k, stack_lim_k, key, key_pexec_idx,
 
         if not self.platform.no_user_change:
             self.platform.make_fresh_krun_user()
+            # If we are in instrumentation mode, grant the Krun user write
+            # access to the instrumentation directory.
+            if self.instrument:
+                util.set_instr_dir_perms(self.config, self.platform)
 
         wrapper_filename, envlog_filename = \
             self.make_wrapper_script(args, heap_lim_k, stack_lim_k)