On 12/21/2010 05:05 AM, Wen Congyang wrote:
When I use the command 'virsh save' to save the domain state,
I receive the following error message:
operation failed: Migration unexpectedly failed.
I debug the qemu by adding some printf(), and find the function
pclose() returns -1.
I use strace to trace qemu, the log is as the following:
======
close(17) = 0
--- SIGCHLD (Child exited) @ 0 (0) ---
wait4(-1, NULL, WNOHANG, NULL) = 22016
rt_sigreturn(0) = 0
wait4(22016, 0x7fff7f1034fc, 0, NULL) = -1 ECHILD (No child processes)
======
We wait the child twice: one is in signal SIGCHLD handling and the other
one is in pclose().
We should disable sigcld handling before calling pclose().
I wondered whether we need SIGCHLD handling at all. fork is called only
from:
- xen_domain_watcher in hw/xen_domainbuild.c
- launch_script in net/tap.c
- SLIRP's fork_exec ("mini inetd")
For the first, the child will always "outlive" the parent. For the
second, we do waitpid in the function. So SLIRP is the only real user
of the SIGCHLD handler and in fact this:
http://www.google.com/codesearch/p?hl=en#tGk9u3ZS0cw/pub/Linux/system/network/serial/slirp-1.0.9.tar.gz|s3yKHVXI6eg/slirp-1.0.9/src/main.c
suggests that the handler came from there (search for do_wait). Would
anybody object to removing the support for Samba under SLIRP and all the
resulting cruft?
Paolo
