Public bug reported: after failure using qemu-kvm-0.14.1 I've tried v1.0, but there's a problem if compiled with vnc-thread-support:
Program received signal SIGSEGV, Segmentation fault. 0x0000000000000000 in ?? () (gdb) bt #0 0x0000000000000000 in ?? () #1 0x00007f3ac48ca10a in qemu_iohandler_poll (readfds=0x7fff12379ac0, writefds=0x7fff12379b40, xfds=0x7fff12379bc0, ret=3) at iohandler.c:124 #2 0x00007f3ac4964387 in main_loop_wait (nonblocking=0) at main-loop.c:463 #3 0x00007f3ac4958fb1 in main_loop () at /opt/workspace/oneiric64/qemu-kvm-1.0/vl.c:1482 #4 0x00007f3ac495e1ec in main (argc=68, argv=0x7fff1237a088, envp=0x7fff1237a2b0) at /opt/workspace/oneiric64/qemu-kvm-1.0/vl.c:3523 (gdb) up #1 0x00007f3ac48ca10a in qemu_iohandler_poll (readfds=0x7fff12379ac0, writefds=0x7fff12379b40, xfds=0x7fff12379bc0, ret=3) at iohandler.c:124 124 ioh->fd_write(ioh->opaque); (gdb) print *ioh $4 = {fd = 29, fd_read_poll = 0, fd_read = 0x7f3ac49de158 <vnc_client_read>, fd_write = 0, deleted = 0, opaque = 0x7f3ac7978d50, next = {le_next = 0x7f3ac6add2e0, le_prev = 0x7f3ac52bde90}} ok, how could that happen? loooking deeper at the code and backtraces shows, that iohandler.c:124 is called within the main-loop, while iohandler.c:77 is called within the vnc-thread-loop mmmh, but where the hell is the threadsafe-locking of the ioh- structure???? I didn't found anything... the resetting in line 77 is called from vnc_client_write_plain(), where following code can be found: =================== if (vs->output.offset == 0) { qemu_set_fd_handler2(vs->csock, NULL, vnc_client_read, NULL, vs); } =================== why should the function-ptrs should be zeroed? further tracing shows, that the vnc-thread sometimes seems to exits normally and a new one is started (I haven't verified that), but this would be a reason for zeroing function-ptrs, which may point to code inside the thread, which will exit... but why should this be done? and why there's no threadsafe-modification of the structure? well: disabling vnc-thread at configure-state leads into a normal running machine, but threading would be nice here... so a quick fix could be, to drop the call above and make the vnc-thread staying for the whole session, but I don't know all mechanisms of vnc-support within kvm. but a better solution would be usage of clean locking-mechanisms ** Affects: qemu-kvm (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/974229 Title: qemu-kvm-1.0: segfault using vnc-console => not threadsafe! To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/974229/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs