From 9d61a50bdde64762be68ee9fe7f7d5ba11f086df Mon Sep 17 00:00:00 2001 From: Markus Armbruster Date: Tue, 28 Jul 2009 14:33:41 -0400 Subject: Fix VM state change handlers running out of order When a VM state change handler changes VM state, other VM state change handlers can see the state transitions out of order. bmdma_map(), scsi_disk_init() and virtio_blk_init() install VM state change handlers to restart DMA. These handlers can vm_stop() by running into a write error on a drive with werror=stop. This throws the VM state change handler callback into disarray. Here's an example case I observed: 0. The virtual IDE drive goes south. All future writes return errors. 1. Something encounters a write error, and duly stops the VM with vm_stop(). 2. vm_stop() calls vm_state_notify(0). 3. vm_state_notify() runs the callbacks in list vm_change_state_head. It contains ide_dma_restart_cb() installed by bmdma_map(). It also contains audio_vm_change_state_handler() installed by audio_init(). 4. audio_vm_change_state_handler() stops audio stuff. 5. User continues VM with monitor command "c". This runs vm_start(). 6. vm_start() calls vm_state_notify(1). 7. vm_state_notify() runs the callbacks in vm_change_state_head. 8. ide_dma_restart_cb() happens to come first. It does its work, runs into a write error, and duly stops the VM with vm_stop(). 9. vm_stop() runs vm_state_notify(0). 10. vm_state_notify() runs the callbacks in vm_change_state_head. 11. audio_vm_change_state_handler() stops audio stuff. Which isn't running. 12. vm_stop() finishes, ide_dma_restart_cb() finishes, step 7's vm_state_notify() resumes running handlers. 13. audio_vm_change_state_handler() starts audio stuff. Oopsie. Fix this by moving the actual write from each VM state change handler into a new bottom half (suggested by Gleb Natapov). Signed-off-by: Markus Armbruster Signed-off-by: Anthony Liguori --- hw/ide.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) (limited to 'hw/ide.c') diff --git a/hw/ide.c b/hw/ide.c index 1e56786f18..2eea43835c 100644 --- a/hw/ide.c +++ b/hw/ide.c @@ -501,6 +501,7 @@ typedef struct BMDMAState { QEMUIOVector qiov; int64_t sector_num; uint32_t nsector; + QEMUBH *bh; } BMDMAState; typedef struct PCIIDEState { @@ -1109,11 +1110,13 @@ static void ide_sector_write(IDEState *s) } } -static void ide_dma_restart_cb(void *opaque, int running, int reason) +static void ide_dma_restart_bh(void *opaque) { BMDMAState *bm = opaque; - if (!running) - return; + + qemu_bh_delete(bm->bh); + bm->bh = NULL; + if (bm->status & BM_STATUS_DMA_RETRY) { bm->status &= ~BM_STATUS_DMA_RETRY; ide_dma_restart(bm->ide_if); @@ -1123,6 +1126,19 @@ static void ide_dma_restart_cb(void *opaque, int running, int reason) } } +static void ide_dma_restart_cb(void *opaque, int running, int reason) +{ + BMDMAState *bm = opaque; + + if (!running) + return; + + if (!bm->bh) { + bm->bh = qemu_bh_new(ide_dma_restart_bh, bm); + qemu_bh_schedule(bm->bh); + } +} + static void ide_write_dma_cb(void *opaque, int ret) { BMDMAState *bm = opaque; -- cgit v1.2.1