[gnome-continuous-yocto/gnomeostree-3.28-rocko: 98/218] uninative.bbclass: Fix broken symlink issue

[Emmanuele Bassi <ebassi src gnome org>]

commit 04395b3336e89169ef0c8c160dea8ab72090f57a
Author: Mark Hatle <mark hatle windriver com>
Date:   Tue Jan 23 14:56:18 2018 -0200

    uninative.bbclass: Fix broken symlink issue
    
    If two builds are sharing the same DL_DIR, and the uninative file is local
    to a layer.  When the first build gets to uninative it creates the link local
    to itself, and subsequent users can use the same link.  However if that first
    build then is deleted from the disk, the symlink is no longer valid (broken).
    
    We need to update the system to detect this case, and use the model
    implemented by the bitbke fetch2 code.  Look for a broken link, remove it,
    then try to create the link and ignore an exception if it already exists
    (since we just unlinked any bad one).
    
    (From OE-Core rev: 32895152580152c6613a4d651ba1bcee9be9883f)
    
    Signed-off-by: Mark Hatle <mark hatle windriver com>
    Signed-off-by: Richard Purdie <richard purdie linuxfoundation org>
    (cherry picked from commit bfd9664edad7044b5da53fc33b8d0f6508f00950)
    Signed-off-by: Otavio Salvador <otavio ossystems com br>
    Signed-off-by: Armin Kuster <akuster808 gmail com>
    Signed-off-by: Richard Purdie <richard purdie linuxfoundation org>

 meta/classes/uninative.bbclass |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)
---
diff --git a/meta/classes/uninative.bbclass b/meta/classes/uninative.bbclass
index a410647..670efa9 100644
--- a/meta/classes/uninative.bbclass
+++ b/meta/classes/uninative.bbclass
@@ -63,7 +63,19 @@ python uninative_event_fetchloader() {
             fetcher.download()
             localpath = fetcher.localpath(srcuri)
             if localpath != tarballpath and os.path.exists(localpath) and not os.path.exists(tarballpath):
+                # Follow the symlink behavior from the bitbake fetch2.
+                # This will cover the case where an existing symlink is broken
+                # as well as if there are two processes trying to create it
+                # at the same time.
+                if os.path.islink(tarballpath):
+                    # Broken symbolic link
+                    os.unlink(tarballpath)
+
+                # Deal with two processes trying to make symlink at once
+                try:
                     os.symlink(localpath, tarballpath)
+                except FileExistsError:
+                    pass
 
         cmd = d.expand("\
 mkdir -p ${UNINATIVE_STAGING_DIR}-uninative; \