From 86f1e4e2f57af82aae0944ed704ab91dc36fc9b7 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Fri, 28 Oct 2011 05:28:13 -0400 Subject: [PATCH 2/2] dma: Avoid reentrancy in DMA transfer handlers 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 --- hw/dma.c | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-) diff --git a/hw/dma.c b/hw/dma.c index 8a7302a..0a9322d 100644 --- a/hw/dma.c +++ b/hw/dma.c @@ -358,6 +358,14 @@ static void DMA_run (void) struct dma_cont *d; int icont, ichan; int rearm = 0; + static int running = 0; + + if (running) { + rearm = 1; + goto out; + } else { + running = 1; + } d = dma_controllers; @@ -374,6 +382,8 @@ static void DMA_run (void) } } + running = 0; +out: if (rearm) qemu_bh_schedule_idle(dma_bh); } -- 1.7.7.5