From af7b96c14a555805a50f13a1fa1343650db184ab Mon Sep 17 00:00:00 2001
From: Todd Gamblin <tgamblin@llnl.gov>
Date: Tue, 27 Oct 2015 00:35:06 -0700
Subject: [PATCH] Lock acquires return True/False depending on whether they got
POSIX lock.
---
lib/spack/llnl/util/lock.py | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)
diff --git a/lib/spack/llnl/util/lock.py b/lib/spack/llnl/util/lock.py
index 6e49bf74e6..dcca37687e 100644
--- a/lib/spack/llnl/util/lock.py
+++ b/lib/spack/llnl/util/lock.py
@@ -95,10 +95,15 @@ def acquire_read(self, timeout=_default_timeout):
order, but the POSIX lock is held until all local read and
write locks are released.
+ Returns True if it is the first acquire and actually acquires
+ the POSIX lock, False if it is a nested transaction.
+
"""
- if self._reads == 0 and self._writes == 0:
- self._lock(fcntl.LOCK_SH, timeout)
self._reads += 1
+ if self._reads == 1 and self._writes == 0:
+ self._lock(fcntl.LOCK_SH, timeout)
+ return True
+ return False
def acquire_write(self, timeout=_default_timeout):
@@ -107,10 +112,16 @@ def acquire_write(self, timeout=_default_timeout):
Read and write locks can be acquired and released in arbitrary
order, but the POSIX lock is held until all local read and
write locks are released.
+
+ Returns True if it is the first acquire and actually acquires
+ the POSIX lock, False if it is a nested transaction.
+
"""
- if self._writes == 0:
- self._lock(fcntl.LOCK_EX, timeout)
self._writes += 1
+ if self._writes == 1:
+ self._lock(fcntl.LOCK_EX, timeout)
+ return True
+ return False
def release_read(self):
--
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