bitbake: fetch/wget: mitigate a wget race condition when listing FTP directories

When wget is fetching a listing for a directory over FTP it writes to a
temporary file called .listing in the current directory.  If there are many such
operations happening in parallel - for example during 'bitbake world -c
checkpkg' - then up to BB_NUMBER_THREADS instances of wget will be racing to
write to, read, and delete the same file.

This results in various failures such as the file disappearing before wget has
processed it or the file changing contents, which causes checkpkg to randomly
fail.

Mitigate the race condition by creating a temporary directory to run wget in
when doing directory listings.

[ YOCTO #11828 ]

(Bitbake rev: 91d4ca93df092cf86ab84faaa94cc66ff9f43057)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/fetch2/wget.py

@@ -90,13 +90,13 @@ class Wget(FetchMethod):
 
         self.basecmd = d.getVar("FETCHCMD_wget") or "/usr/bin/env wget -t 2 -T 30 --passive-ftp --no-check-certificate"
 
-    def _runwget(self, ud, d, command, quiet):
+    def _runwget(self, ud, d, command, quiet, workdir=None):
 
         progresshandler = WgetProgressHandler(d)
 
         logger.debug(2, "Fetching %s using command '%s'" % (ud.url, command))
         bb.fetch2.check_network_access(d, command, ud.url)
-        runfetchcmd(command + ' --progress=dot -v', d, quiet, log=progresshandler)
+        runfetchcmd(command + ' --progress=dot -v', d, quiet, log=progresshandler, workdir=workdir)
 
     def download(self, ud, d):
         """Fetch urls"""
@@ -422,17 +422,16 @@ class Wget(FetchMethod):
         Run fetch checkstatus to get directory information
         """
         f = tempfile.NamedTemporaryFile()
+        with tempfile.TemporaryDirectory(prefix="wget-index-") as workdir, tempfile.NamedTemporaryFile(dir=workdir, prefix="wget-listing-") as f:
+            agent = "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.12) Gecko/20101027 Ubuntu/9.10 (karmic) Firefox/3.6.12"
+            fetchcmd = self.basecmd
+            fetchcmd += " -O " + f.name + " --user-agent='" + agent + "' '" + uri + "'"
+            try:
+                self._runwget(ud, d, fetchcmd, True, workdir=workdir)
+                fetchresult = f.read()
+            except bb.fetch2.BBFetchException:
+                fetchresult = ""
 
-        agent = "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.12) Gecko/20101027 Ubuntu/9.10 (karmic) Firefox/3.6.12"
-        fetchcmd = self.basecmd
-        fetchcmd += " -O " + f.name + " --user-agent='" + agent + "' '" + uri + "'"
-        try:
-            self._runwget(ud, d, fetchcmd, True)
-            fetchresult = f.read()
-        except bb.fetch2.BBFetchException:
-            fetchresult = ""
-
-        f.close()
         return fetchresult
 
     def _check_latest_version(self, url, package, package_regex, current_version, ud, d):