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Message-ID: <4EB0349E.4000401@redhat.com>
Date: Tue, 01 Nov 2011 13:04:14 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH v2] Fix segfault on migration completion
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To: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, Juan Jose Quintela Carreira <quintela@redhat.com>, qemu-devel <qemu-devel@nongnu.org>, Eduardo Habkost <ehabkost@redhat.com>

On 10/28/2011 11:59 AM, Luiz Capitulino wrote:
> A simple migration reproduces it:
>
> 1. Start the source VM with:
>
>     # qemu [...] -S
>
> 2. Start the destination VM with:
>
>     # qemu<source VM cmd-line>  -incoming tcp:0:4444
>
> 3. In the source VM:
>
>     (qemu) migrate -d tcp:0:4444
>
> 4. The source VM will segfault as soon as migration completes (might not
>     happen in the first try)
>
> What is happening here is that qemu_file_put_notify() can end up closing
> 's->file' (in which case it's also set to NULL). The call stack is rather
> complex, but Eduardo helped tracking it to:
>
> select loop ->  migrate_fd_put_notify() ->  qemu_file_put_notify() ->
> buffered_put_buffer() ->  migrate_fd_put_ready() ->
> migrate_fd_completed() ->  migrate_fd_cleanup().
>
> To be honest, it's not completely clear to me in which cases 's->file'
> is not closed (on error maybe)? But I doubt this fix will make anything
> worse.
>
> Reviewed-by: Paolo Bonzini<pbonzini@redhat.com>
> Acked-by: Eduardo Habkost<ehabkost@redhat.com>
> Signed-off-by: Luiz Capitulino<lcapitulino@redhat.com>

Applied.  Thanks.

Regards,

Anthony Liguori

> ---
>
> V2: better commit log
>
>   migration.c |    2 +-
>   1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/migration.c b/migration.c
> index bdca72e..f6e6208 100644
> --- a/migration.c
> +++ b/migration.c
> @@ -252,7 +252,7 @@ static void migrate_fd_put_notify(void *opaque)
>
>       qemu_set_fd_handler2(s->fd, NULL, NULL, NULL, NULL);
>       qemu_file_put_notify(s->file);
> -    if (qemu_file_get_error(s->file)) {
> +    if (s->file&&  qemu_file_get_error(s->file)) {
>           migrate_fd_error(s);
>       }
>   }