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Re: [libvirt] [PATCH] cmdMigrate: move vshConnect before vshWatchJob



On 08/08/2014 10:44 AM, Chunyan Liu wrote:
> A possible fix to issue:
> http://www.redhat.com/archives/libvir-list/2014-August/thread.html#00227
> 
> While doing migration on KVM host, found problem sometimes:
> VM is already running on the target host and disappears from source
> host, but 'virsh migrate' command line hangs, cannot exit normally.
> If pressing "ENTER" key, it will exit.
> 
> The code hangs at tools/virsh-domain.c: cmdMigrate
> ->vshWatchJob->poll():
> poll() is trying to select pipe_fd, which is used to receive message
> from doMigrate thread. In debugging, found that doMigrate finishes
> and at the end it does call safewrite() to write the retval ('0' or
> '1') to pipe_fd, and the write is completed. But cmdMigrate poll()
> cannot get the event. If pressing "ENTER" key, poll() can get the
> event and select pipe_fd, then command line can exit.
> 
> In current code, authentication thread which is called by vshConnect
> will use stdin, and at the same time, in cmdMigrate main process,
> poll() is listening to stdin, that probably affect poll() to get
> pipe_fd event. Better to move authentication before vshWatchJob. With
> this change, above problem does not exist.
> 
> Signed-off-by: Chunyan Liu <cyliu suse com>
> ---
>  tools/virsh-domain.c | 26 ++++++++++++++++++++------
>  tools/virsh.h        |  1 +
>  2 files changed, 21 insertions(+), 6 deletions(-)

ACK

> diff --git a/tools/virsh-domain.c b/tools/virsh-domain.c
> index f7193cb..2562326 100644
> --- a/tools/virsh-domain.c
> +++ b/tools/virsh-domain.c
> @@ -8965,6 +8965,7 @@ doMigrate(void *opaque)
>      virTypedParameterPtr params = NULL;
>      int nparams = 0;
>      int maxparams = 0;
> +    virConnectPtr dconn = data->dconn;
>  
>      sigemptyset(&sigmask);
>      sigaddset(&sigmask, SIGINT);
> @@ -9079,18 +9080,12 @@ doMigrate(void *opaque)
>              ret = '0';
>      } else {

I'd rather rewrite this condition as:
if (dconn) {
  /* Traditional live migration */
} else {
  /* peer2peer or direct */
}



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