install : finer graned locking for install command

lib/spack/llnl/util/lock.py

@@ -28,9 +28,13 @@
 import time
 import socket
 
+import llnl.util.tty as tty
+
+
 __all__ = ['Lock', 'LockTransaction', 'WriteTransaction', 'ReadTransaction',
            'LockError']
 
+
 # Default timeout in seconds, after which locks will raise exceptions.
 _default_timeout = 60
 
@@ -120,6 +124,7 @@ def acquire_read(self, timeout=_default_timeout):
 
         """
         if self._reads == 0 and self._writes == 0:
+            tty.debug('READ LOCK : {0._file_path} [Acquiring]'.format(self))
             self._lock(fcntl.LOCK_SH, timeout)   # can raise LockError.
             self._reads += 1
             return True
@@ -139,6 +144,7 @@ def acquire_write(self, timeout=_default_timeout):
 
         """
         if self._writes == 0:
+            tty.debug('WRITE LOCK : {0._file_path} [Acquiring]'.format(self))
             self._lock(fcntl.LOCK_EX, timeout)   # can raise LockError.
             self._writes += 1
             return True
@@ -159,6 +165,7 @@ def release_read(self):
         assert self._reads > 0
 
         if self._reads == 1 and self._writes == 0:
+            tty.debug('READ LOCK : {0._file_path} [Released]'.format(self))
             self._unlock()      # can raise LockError.
             self._reads -= 1
             return True
@@ -179,6 +186,7 @@ def release_write(self):
         assert self._writes > 0
 
         if self._writes == 1 and self._reads == 0:
+            tty.debug('WRITE LOCK : {0._file_path} [Released]'.format(self))
             self._unlock()      # can raise LockError.
             self._writes -= 1
             return True