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From: Jason Wang <jasowang@redhat.com>
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Date: Thu, 28 Apr 2016 15:16:32 +0800
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Subject: Re: [Qemu-devel] [RFC PATCH V3 1/4] colo-compare: introduce colo
 compare initlization
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To: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>, qemu devel <qemu-devel@nongnu.org>
Cc: Li Zhijian <lizhijian@cn.fujitsu.com>, Gui jianfeng <guijianfeng@cn.fujitsu.com>, "eddie.dong" <eddie.dong@intel.com>, zhanghailiang <zhang.zhanghailiang@huawei.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>, Yang Hongyang <hongyang.yang@easystack.cn>



On 04/28/2016 02:53 PM, Jason Wang wrote:
> +static void compare_set_outdev(Object *obj, const char *value, Error **errp)
> > +{
> > +    CompareState *s = COLO_COMPARE(obj);
> > +
> > +    g_free(s->outdev);
> > +    s->outdev = g_strdup(value);
> > +}
> > +
> > +/*
> > + * called from the main thread on the primary
> > + * to setup colo-compare.
> > + */
> > +static void colo_compare_complete(UserCreatable *uc, Error **errp)
> > +{
> > +    CompareState *s = COLO_COMPARE(uc);
> > +
> > +    if (!s->pri_indev || !s->sec_indev || !s->outdev) {
> > +        error_setg(errp, "colo compare needs 'primary_in' ,"
> > +                   "'secondary_in','outdev' property set");
> > +        return;
> > +    } else if (!strcmp(s->pri_indev, s->outdev) ||
> > +               !strcmp(s->sec_indev, s->outdev) ||
> > +               !strcmp(s->pri_indev, s->sec_indev)) {
> > +        error_setg(errp, "'indev' and 'outdev' could not be same "
> > +                   "for compare module");
> > +        return;
> > +    }
> > +
> > +    s->chr_pri_in = qemu_chr_find(s->pri_indev);
> > +    if (s->chr_pri_in == NULL) {
> > +        error_setg(errp, "Primary IN Device '%s' not found",
> > +                   s->pri_indev);
> > +        return;
> > +    }
> > +
> > +    s->chr_sec_in = qemu_chr_find(s->sec_indev);
> > +    if (s->chr_sec_in == NULL) {
> > +        error_setg(errp, "Secondary IN Device '%s' not found",
> > +                   s->sec_indev);
> > +        return;
> > +    }
> > +
> > +    s->chr_out = qemu_chr_find(s->outdev);
> > +    if (s->chr_out == NULL) {
> > +        error_setg(errp, "OUT Device '%s' not found", s->outdev);
> > +        return;
> > +    }
> > +
> > +    qemu_chr_fe_claim_no_fail(s->chr_pri_in);
> > +    qemu_chr_add_handlers(s->chr_pri_in, compare_chr_can_read,
> > +                          compare_pri_chr_in, NULL, s);
> > +
> > +    qemu_chr_fe_claim_no_fail(s->chr_sec_in);
> > +    qemu_chr_add_handlers(s->chr_sec_in, compare_chr_can_read,
> > +                          compare_sec_chr_in, NULL, s);
> > +

Btw, what's the reason of handling this in main loop? I thought it would
be better to do this in colo thread? Otherwise, you need lots of extra
synchronizations?

> > +    qemu_chr_fe_claim_no_fail(s->chr_out);
> > +    QTAILQ_INSERT_TAIL(&net_compares, s, next);
> > +
> > +    return;
> > +}