| Message ID | 156688661263.3027.3336339084032447737.malone@chaenomeles.canonical.com |
|---|---|
| State | New |
| Headers | show |
| Series | [Bug,1839428] Re: qemu core dumped when repeat "system_reset" multiple times during guest boot | expand |
diff --git a/block.c b/block.c index 4ad0e90d7e..0c12632661 100644 --- a/block.c +++ b/block.c @@ -5265,6 +5265,10 @@ void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context) { AioContext *ctx = bdrv_get_aio_context(bs); + if (ctx == new_context) { + return; + } + aio_disable_external(ctx); bdrv_parent_drained_begin(bs, NULL, false); bdrv_drain(bs); /* ensure there are no in-flight requests */
I found the commit that introduced this regression. commit 57830a499f7c815bb0cb325c94a3d8c910d13cfa (HEAD) Author: Denis Plotnikov <dplotnikov@virtuozzo.com> Date: Fri Feb 15 16:03:25 2019 +0300 block: don't set the same context Adds a fast path on aio context setting preventing unnecessary context setting routine. Also, it prevents issues with cyclic walk of child bds-es appeared because of registering aio walking notifiers: Call stack: 0 __GI_raise 1 __GI_abort 2 __assert_fail_base 3 __GI___assert_fail 4 bdrv_detach_aio_context (bs=0x55f54d65c000) <<< 5 bdrv_detach_aio_context (bs=0x55f54fc8a800) 6 bdrv_set_aio_context (bs=0x55f54fc8a800, ...) 7 block_job_attached_aio_context 8 bdrv_attach_aio_context (bs=0x55f54d65c000, ...) <<< 9 bdrv_set_aio_context (bs=0x55f54d65c000) 10 blk_set_aio_context 11 virtio_blk_data_plane_stop 12 virtio_bus_stop_ioeventfd 13 virtio_vmstate_change 14 vm_state_notify (running=0, state=RUN_STATE_SHUTDOWN) 15 do_vm_stop (state=RUN_STATE_SHUTDOWN, send_stop=true) 16 vm_stop (state=RUN_STATE_SHUTDOWN) 17 main_loop_should_exit 18 main_loop 19 main This can happen because of "new" context attachment to VM disk bds. When attaching a new context the corresponding aio context handler is called for each of aio_notifiers registered on the VM disk bds context. Among those handlers, there is the block_job_attached_aio_context handler which sets a new aio context for the block job bds. When doing so, the old context is detached from all the block job bds children and one of them is the VM disk bds, serving as backing store for the blockjob bds, although the VM disk bds is actually the initializer of that process. Since the VM disk bds is protected with walking_aio_notifiers flag from double processing in recursive calls, the assert fires. Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>