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Consider when there is a double fork of helpers or zombies, e.g. when a
zombie has a session id which doesn't match its pid. If the child dies and
exits before the grandchild, the grandchild reparents to init, and when the
task dies init doesn't have it in the helper list, so init dies as well,
viz. the log below.
(00.118789) Add a helper 293 for restoring SID 293
(00.118792) Attach 294 to the temporary task 293
...
(01.394403) 294: Restoring zombie with 0 code
...
pie: Task 294 exited, status= 0
(01.434279) Error (cr-restore.c:1308): 12097 killed by signal 19
(01.434420) Error (cr-restore.c:1308): 12097 killed by signal 19
(01.450258) Switching to new ns to clean ghosts
(01.450324) Error (cr-restore.c:2138): Restoring FAILED.
Let's have the helpers reap their children before they exit to avoid this.
v2: block SIGCHLD when waiting on helpers so that it doesn't race with the
SICGHLD handler
v3: * only helpers should collect their children, zombies can't have kids
* don't double decrement nr_tasks in zombie case
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
CRIU (Checkpoint and Restore in Userspace)
An utility to checkpoint/restore tasks. Using this tool, you can freeze a running application (or part of it) and checkpoint it to a hard drive as a collection of files. You can then use the files to restore and run the application from the point it was frozen at. The distinctive feature of the CRIU project is that it is mainly implemented in user space.
The project home is at http://criu.org.
Pages worth starting with are:
- Kernel configuration, compilation, etc
- A simple example of usage
- More sophisticated example with graphical app
How to contribute
- How to submit patches;
- Send all bug reports to mailing list;
- Spread the word about CRIU in social networks;