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authorKevin Wolf <kwolf@redhat.com>2011-10-28 05:28:13 -0400
committerKevin Wolf <kwolf@redhat.com>2011-11-04 14:23:58 +0100
commitacae6f1c4c1dae1b7e059751347ca4225b01a391 (patch)
tree971c2671b8fa18543ae97d9aeef1b3115271d728
parent67403dbba76fb294fb3a2317227f4b77037145cc (diff)
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 <kwolf@redhat.com>
-rw-r--r--hw/dma.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/hw/dma.c b/hw/dma.c
index 8a7302a42f..0a9322daa3 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);
}