qemu may segfault when a BH handler first deletes a BH and then (possibly
indirectly) calls a nested qemu_bh_poll(). This is because the inner instance
frees the BH and deletes it from the list that the outer one processes.
This patch deletes BHs only in the outermost qemu_bh_poll instance.
Commit 7887f620 already tried to achieve the same, but it assumed that the BH
handler would only delete its own BH. With a nested qemu_bh_poll(), this isn't
guaranteed, so that commit wasn't enough. Hope this one fixes it for real.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The purpose of AsyncContexts was to protect qcow and qcow2 against reentrancy
during an emulated bdrv_read/write (which includes a qemu_aio_wait() call and
can run AIO callbacks of different requests if it weren't for AsyncContexts).
Now both qcow and qcow2 are protected by CoMutexes and AsyncContexts can be
removed.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Without this, qemu segfaults when a BH handler first deletes its BH and
then calls another function which involves a nested qemu_bh_poll() call.
This can be reproduced by generating an I/O error (e.g. with blkdebug) on
an IDE device and using rerror/werror=stop to stop the VM. When continuing
the VM, qemu segfaults.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Add the possibility to use AIO and BHs without allowing foreign callbacks to be
run. Basically, you put your own AIOs and BHs in a separate context. For
details see the comments in the source.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Instead of putting more and more stuff into vl.c, let's have the generic
functions that deal with asynchronous callbacks in their own file.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Paolo Bonzini