From c039e998f2cb65405c65fb1fa0b2c2c5c90b4222 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Tue, 14 Feb 2012 11:14:16 +0100 Subject: [PATCH 51/99] dma: Avoid reentrancy in DMA transfer handlers RH-Author: Kevin Wolf Message-id: <1329218101-24213-52-git-send-email-kwolf@redhat.com> Patchwork-id: 37245 O-Subject: [RHEL-6.3 qemu-kvm PATCH v2 51/96] dma: Avoid reentrancy in DMA transfer handlers Bugzilla: 783950 RH-Acked-by: Paolo Bonzini RH-Acked-by: Marcelo Tosatti RH-Acked-by: Laszlo Ersek Bugzilla: 783950 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 (cherry picked from commit acae6f1c4c1dae1b7e059751347ca4225b01a391) --- hw/dma.c | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-) Signed-off-by: Michal Novotny --- hw/dma.c | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-) diff --git a/hw/dma.c b/hw/dma.c index fe69ddd..0d7b431 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