Am 21.07.2011 17:23, schrieb Stefan Hajnoczi: > On Fri, Jul 15, 2011 at 06:47:39PM +0200, Kevin Wolf wrote: >> If we're already in a coroutine, there is no reason to use the synchronous >> version of block layer functions when a coroutine one exists. This makes >> bdrv_read/write/flush use bdrv_co_* when used inside a coroutine. >> >> Signed-off-by: Kevin Wolf <kw...@redhat.com> >> --- >> block.c | 43 +++++++++++++++++++++++++++++++++++++++++++ >> 1 files changed, 43 insertions(+), 0 deletions(-) > > I made similar changes to prototype qcow2 coroutines. They allowed > synchronous code to run unmodified inside a coroutine. > > But do we want to keep the synchronous APIs? They tend to be misused > because they allow synchronous implementation of devices (extboot, > onenand, and others). > > The only reason to keep these around is for qemu-img and perhaps some > startup code before the VM is running. But I think we could tackle > those cases too simply by running in a coroutine and using a common > event loop (which makes timers and bottom halves work too).
One change at a time. :-) This series is manageable, can be reviewed in finite time and gives us the immediate benefit of not blocking the VCPU any more. I know that some tend to rewrite half of qemu for every idea they have, but I'd prefer a more incremental approach. Removing all synchronous bdrv_read/write calls from the devices is a task that I wouldn't underestimate, and at the same time a completely unrelated task (you could have suggested the same with AIO callbacks). I agree that we should do this change some time, but for now devices get exactly what they got before. Kevin
