On 10/28/2011 04:18 PM, Kevin Wolf wrote:
With the conversion of the block layer to coroutines, bdrv_read/write have changed to run a nested event loop that calls qemu_bh_poll. Consequently a scheduled BH can be called while a DMA transfer handler runs and this means that DMA_run becomes reentrant.Devices haven't been designed to cope with that, so instead of running a nested transfer handler just wait for the next invocation of the BH from the main loop. This fixes some problems with the floppy device. Signed-off-by: Kevin Wolf<kw...@redhat.com> --- hw/dma.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-) diff --git a/hw/dma.c b/hw/dma.c index 8a7302a..e8d6341 100644 --- a/hw/dma.c +++ b/hw/dma.c @@ -358,6 +358,13 @@ static void DMA_run (void) struct dma_cont *d; int icont, ichan; int rearm = 0; + static int running = 0; + + if (running) { + goto out; + } else { + running = 1; + } d = dma_controllers; @@ -374,6 +381,8 @@ static void DMA_run (void) } } +out: + running = 0; if (rearm) qemu_bh_schedule_idle(dma_bh); }
Hmm, I think you should set rearm = 1 to ensure the BH is run when ultimately you leave the sync read. Sorry for not spotting this before.
Paolo
