[PATCH 0/1] qemurunner.py: fix race condition at qemu startup

[PATCH 0/1] qemurunner.py: fix race condition at qemu startup

[Chen Qi]

*** BLURB HERE ***
The following changes since commit 80ab79168ede2786868cbd354f0950c949f73527:

  gnome-themes-standard: remove (2019-07-11 09:32:50 +0100)

are available in the git repository at:

  git://git.pokylinux.org/poky-contrib ChenQi/qemurunner-race
  http://git.pokylinux.org/cgit.cgi/poky-contrib/log/?h=ChenQi/qemurunner-race

Chen Qi (1):
  qemurunner.py: fix race condition at qemu startup

 meta/lib/oeqa/utils/qemurunner.py | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

-- 
1.9.1

[PATCH 1/1] qemurunner.py: fix race condition at qemu startup

[Chen Qi]

When handling pid file, qemu would first create the file, stat it,
lock it and then write actually contents to it.

So it's possbile that when reading the pid file, the content is empty.

[YOCTO #13390]

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
---
 meta/lib/oeqa/utils/qemurunner.py | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/meta/lib/oeqa/utils/qemurunner.py b/meta/lib/oeqa/utils/qemurunner.py
index c16227f..68684ae 100644
--- a/meta/lib/oeqa/utils/qemurunner.py
+++ b/meta/lib/oeqa/utils/qemurunner.py
@@ -425,13 +425,20 @@ class QemuRunner:
         if not self.runqemu or self.runqemu.poll() is not None:
             return False
         if os.path.isfile(self.qemu_pidfile):
-            f = open(self.qemu_pidfile, 'r')
-            qemu_pid = f.read()
-            f.close()
-            qemupid = int(qemu_pid)
-            if os.path.exists("/proc/" + str(qemupid)):
-                self.qemupid = qemupid
-                return True
+            # when handling pidfile, qemu creates the file, stat it, lock it and then write to it
+            # so it's possible that the file has been created but the content is empty
+            pidfile_timeout = time.time() + 3
+            while time.time() < pidfile_timeout:
+                with open(self.qemu_pidfile, 'r') as f:
+                    qemu_pid = f.read().strip()
+                # file created but not yet written contents
+                if not qemu_pid:
+                    time.sleep(0.5)
+                    continue
+                else:
+                    if os.path.exists("/proc/" + qemu_pid):
+                        self.qemupid = int(qemu_pid)
+                        return True
         return False
 
     def run_serial(self, command, raw=False, timeout=60):
-- 
1.9.1