Re: [Qemu-devel] [PATCH v3 4/4] hw/qxl-render: drop cursor locks, replace with pipe

[Alon Levy]

On Wed, Mar 16, 2011 at 05:48:41PM +0100, Jes Sorensen wrote:
> On 03/16/11 16:52, Alon Levy wrote:
> > +void qxl_server_request_cursor_set(PCIQXLDevice *qxl, QEMUCursor *c, int 
> > x, int y)
> > +{
> > +    QXLServerCursorSetRequest req;
> > +    int r;
> > +
> > +    req.req = QXL_SERVER_CURSOR_SET;
> > +    req.data.c = c;
> > +    req.data.x = x;
> > +    req.data.y = y;
> > +    r = write(qxl->ssd.pipe[1], &req, sizeof(req));
> > +    assert(r == sizeof(req));
> > +}
> 
> There's a number of asserts here, which I am not sure is a good thing. I
> don't understand how far down the code this is, and if it is really
> fatal if this write fails?

A failure there means we can't write to a pipe between the server thread
and the iothread (main thread). That is not supposed to happen - and if
it does it means some operation by the spice server will never complete.

Same for the asserts below, writes are from spice server thread, reads
are in iothread.

> 
> > +/* called from spice server thread context only */
> > +void qxl_server_request_cursor_move(PCIQXLDevice *qxl, int x, int y)
> > +{
> > +    QXLServerCursorMoveRequest req;
> > +    int r;
> > +
> > +    req.req = QXL_SERVER_CURSOR_MOVE;
> > +    req.data.x = x;
> > +    req.data.y = y;
> > +    r = write(qxl->ssd.pipe[1], &req, sizeof(req));
> > +    assert(r == sizeof(req));
> 
> ditto
> 
> > +static void read_bytes(int fd, void *buf, int len_requested)
> > +{
> > +    int len;
> > +    int total_len = 0;
> > +
> > +    do {
> > +        len = read(fd, buf, len_requested - total_len);
> > +        if (len < 0) {
> > +            if (errno == EINTR || errno == EAGAIN) {
> > +                continue;
> > +            }
> > +            perror("qxl: pipe_read: read failed");
> > +            /* will abort once it's out of the while loop */
> > +            break;
> > +        }
> > +        total_len += len;
> > +        buf = (uint8_t *)buf + len;
> > +    } while (total_len < len_requested);
> > +    assert(total_len == len_requested);
> 
> and here?
> 
> Cheers,
> Jes
> 
> 
>