On 14.06.21 10:29, Emanuele Giuseppe Esposito wrote:
When qemu_coroutine_enter is executed in a loop
(even QEMU_FOREACH_SAFE), the new routine can modify the list,
for example removing an element, causing problem when control
is given back to the caller that continues iterating on the same list.
Patch 1 solves the issue in blkdebug_debug_resume by restarting
the list walk after every coroutine_enter if list has to be fully iterated.
Patches 2,3,4 aim to fix blkdebug_debug_event by gathering
all actions that the rules make in a counter and invoking
the respective coroutine_yeld only after processing all requests.
Patch 5-6 are somewhat independent of the others, patch 5 removes the need
of new_state field, and patch 6 adds a lock to
protect rules and suspended_reqs; right now everything works because
it's protected by the AioContext lock.
This is a preparation for the current proposal of removing the AioContext
lock and instead using smaller granularity locks to allow multiple
iothread execution in the same block device.
Signed-off-by: Emanuele Giuseppe Esposito <eespo...@redhat.com>
---
v5:
* Add comment in patch 1 to explain why we don't need _SAFE in for loop
* Move the state update (s->state = new_state) in patch 5, to maintain
the same existing effect in all patches
I’m not sure whether this actually fixes a user-visible bug…? The first
paragraph makes it sound like it, but there is no test, so I’m not sure.
I’m mostly asking because of freeze; but you make it sound like there’s
a bug, and as this only concerns blkdebug (i.e., a block driver used
only for testing), I feel like applying this series after soft freeze
should be fine, so:
Thanks, I’ve applied this series to my block branch:
https://github.com/XanClic/qemu/commits/block
Max
