From 86f1e4e2f57af82aae0944ed704ab91dc36fc9b7 Mon Sep 17 00:00:00 2001

From: Kevin Wolf <kwolf@redhat.com>

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 <kwolf@redhat.com>

---

 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