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
====================================
Testing head checking code: Case D-4
====================================
Mercurial checks for the introduction of new heads on push. Evolution comes
into play to detect if existing branches on the server are being replaced by
some of the new one we push.
This case is part of a series of tests checking this behavior.
Category D: remote head is "obs-affected" locally, but result is not part of the push
TestCase 4: multi-changeset branch, split on multiple other, (base on its own new branch)
.. old-state:
..
.. * 2 branch (1 changeset, and 2 changesets)
..
.. new-state:
..
.. * 1 new branch superceeding the base of the old-2-changesets-branch,
.. * 1 new changesets on the old-1-changeset-branch superceeding the head of the other
..
.. expected-result:
..
.. * push the new branch only -> push denied (variant a)
.. * push the existing branch only -> push allowed (variant b)
.. (pushing all is tested as case A-7)
..
.. graph-summary:
..
.. (variant a)
..
.. B'○⇢ø B
.. | |
.. A | ø⇠◔ A'
.. | |/
.. C ● |
.. \|
.. ●
..
.. or (variant b)
..
.. B'◔⇢ø B
.. | |
.. A | ø⇠○ A'
.. | |/
.. C ● |
.. \|
.. ●
$ . $TESTDIR/testlib/push-checkheads-util.sh
Test setup
----------
$ mkdir D4
$ cd D4
$ setuprepos
creating basic server and client repo
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd server
$ mkcommit B0
$ hg up 0
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ mkcommit C0
created new head
$ cd ../client
$ hg pull
pulling from $TESTTMP/D4/server (glob)
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 2 files (+1 heads)
(run 'hg heads' to see heads, 'hg merge' to merge)
$ hg up 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ mkcommit A1
created new head
$ hg up 'desc(C0)'
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ mkcommit B1
$ hg debugobsolete `getid "desc(A0)" ` `getid "desc(A1)"`
$ hg debugobsolete `getid "desc(B0)" ` `getid "desc(B1)"`
$ hg log -G --hidden
@ d70a1f75a020 (draft): B1
|
| o f6082bc4ffef (draft): A1
| |
o | 0f88766e02d6 (draft): C0
|/
| x d73caddc5533 (draft): B0
| |
| x 8aaa48160adc (draft): A0
|/
o 1e4be0697311 (public): root
Actual testing (new branch only)
--------------------------------
$ hg push --rev 'desc(A1)'
pushing to $TESTTMP/D4/server (glob)
searching for changes
abort: push creates new remote head f6082bc4ffef!
(merge or see 'hg help push' for details about pushing new heads)
[255]
Actual testing (existing branch only)
------------------------------------
$ hg push --rev 'desc(B1)'
pushing to $TESTTMP/D4/server (glob)
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
1 new obsolescence markers
$ cd ../..