worker: rewrite error handling so os._exit covers all cases
Previously the worker error handling is like:
pid = os.fork() --+
if pid == 0: |
.... | problematic
.... --+
try: --+
.... | worker error handling
--+
If a signal arrives when Python is executing the "problematic" lines, an
external error handling (dispatch.py) will take over the control flow and
it's no longer guaranteed "os._exit" is called (see
86cd09bc13ba for why it
is necessary).
This patch rewrites the error handling so it covers all possible code paths
for a worker even during fork.
Note: "os.getpid() == parentpid" is used to test if the process is parent or
not intentionally, instead of checking "pid", because "pid = os.fork()" may
be not atomic - it's possible that that a signal hits the worker before the
assignment completes [1]. The newly added test replaces "os.fork" to
exercise that extreme case.
[1]: CPython compiles "pid = os.fork()" to 2 byte codes: "CALL_FUNCTION" and
"STORE_FAST", so it's probably not atomic:
def f():
pid = os.fork()
dis.dis(f)
2 0 LOAD_GLOBAL 0 (os)
3 LOAD_ATTR 1 (fork)
6 CALL_FUNCTION 0
9 STORE_FAST 0 (pid)
12 LOAD_CONST 0 (None)
15 RETURN_VALUE
#!/bin/bash -eu
. $(dirname $0)/dockerlib.sh
. $(dirname $0)/packagelib.sh
BUILDDIR=$(dirname $0)
export ROOTDIR=$(cd $BUILDDIR/.. > /dev/null; pwd)
checkdocker
DISTID="$1"
CODENAME="$2"
PLATFORM="$1-$2"
shift; shift # extra params are passed to build process
OUTPUTDIR=${OUTPUTDIR:=$ROOTDIR/packages/$PLATFORM}
initcontainer $PLATFORM
# debuild only appears to be able to save built debs etc to .., so we
# have to share the .. of the current directory with the docker
# container and hope it's writable. Whee.
dn=$(basename $PWD)
if [ $(uname) = "Darwin" ] ; then
$DOCKER run -u $DBUILDUSER --rm -v $PWD/..:/mnt $CONTAINER \
sh -c "cd /mnt/$dn && make clean && make local"
fi
$DOCKER run -u $DBUILDUSER --rm -v $PWD/..:/mnt $CONTAINER \
sh -c "cd /mnt/$dn && DEB_BUILD_OPTIONS='${DEB_BUILD_OPTIONS:=}' contrib/builddeb --build --distid $DISTID --codename $CODENAME $@"
contrib/builddeb --cleanup --distid $DISTID --codename $CODENAME
if [ $(uname) = "Darwin" ] ; then
$DOCKER run -u $DBUILDUSER --rm -v $PWD/..:/mnt $CONTAINER \
sh -c "cd /mnt/$dn && make clean"
fi