[Box Backup-commit] COMMIT r3560 - box/trunk/lib/common
subversion at boxbackup.org
subversion at boxbackup.org
Mon May 4 19:56:53 BST 2015
Author: chris
Date: 2015-05-04 18:56:53 +0000 (Mon, 04 May 2015)
New Revision: 3560
Modified:
box/trunk/lib/common/NamedLock.cpp
Log:
Fix lock race condition by unlinking before closing the file handle.
Modified: box/trunk/lib/common/NamedLock.cpp
===================================================================
--- box/trunk/lib/common/NamedLock.cpp 2015-05-04 18:56:48 UTC (rev 3559)
+++ box/trunk/lib/common/NamedLock.cpp 2015-05-04 18:56:53 UTC (rev 3560)
@@ -207,30 +207,30 @@
{
THROW_EXCEPTION(CommonException, NamedLockNotHeld)
}
-
- // Close the file
- if(::close(mFileDescriptor) != 0)
+
+ // Delete the file. We need to do this before closing the filehandle, otherwise
+ // someone could acquire the lock, release and delete it between us closing (and
+ // hence releasing) and deleting it, and we'd fail when it came to deleting the
+ // file. This happens in tests much more often than you'd expect!
+
+ if(::unlink(mFileName.c_str()) != 0)
{
THROW_EMU_ERROR(
- BOX_FILE_MESSAGE(mFileName, "Failed to close lockfile"),
+ BOX_FILE_MESSAGE(mFileName, "Failed to delete lockfile"),
CommonException, OSFileError);
}
- // Delete the file
- if(::unlink(mFileName.c_str()) != 0)
+ // Close the file
+ if(::close(mFileDescriptor) != 0)
{
THROW_EMU_ERROR(
- BOX_FILE_MESSAGE(mFileName,
- "Failed to delete lockfile"),
+ BOX_FILE_MESSAGE(mFileName, "Failed to close lockfile"),
CommonException, OSFileError);
}
// Mark as unlocked, so we don't try to close it again if the unlink() fails.
mFileDescriptor = -1;
-}
-
-
BOX_TRACE("Released lock and deleted lockfile " << mFileName);
}
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