From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:39943) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RJnqI-0007Rv-Jo for qemu-devel@nongnu.org; Fri, 28 Oct 2011 10:55:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RJnqH-0002sW-LL for qemu-devel@nongnu.org; Fri, 28 Oct 2011 10:55:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:61173) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RJnqH-0002sA-C1 for qemu-devel@nongnu.org; Fri, 28 Oct 2011 10:55:33 -0400 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id p9SEtUGT004396 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Fri, 28 Oct 2011 10:55:31 -0400 From: Kevin Wolf Date: Fri, 28 Oct 2011 16:18:21 +0200 Message-Id: <1319811501-6823-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PATCH] dma: Avoid reentrancy in DMA transfer handlers List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com 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 | 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); } -- 1.7.6.4