[v4,05/25] block/block-backend.c: assertions for block-backend

Commit Message

Emanuele Giuseppe Esposito Oct. 25, 2021, 10:17 a.m. UTC

All the global state (GS) API functions will check that
qemu_in_main_thread() returns true. If not, it means
that the safety of BQL cannot be guaranteed, and
they need to be moved to I/O.

Signed-off-by: Emanuele Giuseppe Esposito <[e-mail]>
Reviewed-by: Stefan Hajnoczi <[e-mail]>
---
 block/block-backend.c  | 90 +++++++++++++++++++++++++++++++++++++++++-
 softmmu/qdev-monitor.c |  2 +
 2 files changed, 91 insertions(+), 1 deletion(-)

Comments

Hanna Czenczek Nov. 12, 2021, 11:01 a.m. UTC | #1

On 25.10.21 12:17, Emanuele Giuseppe Esposito wrote:
> All the global state (GS) API functions will check that
> qemu_in_main_thread() returns true. If not, it means
> that the safety of BQL cannot be guaranteed, and
> they need to be moved to I/O.
>
> Signed-off-by: Emanuele Giuseppe Esposito <[e-mail]>
> Reviewed-by: Stefan Hajnoczi <[e-mail]>
> ---
>   block/block-backend.c  | 90 +++++++++++++++++++++++++++++++++++++++++-
>   softmmu/qdev-monitor.c |  2 +
>   2 files changed, 91 insertions(+), 1 deletion(-)
>
> diff --git a/block/block-backend.c b/block/block-backend.c
> index 0afc03fd66..ed45576007 100644
> --- a/block/block-backend.c
> +++ b/block/block-backend.c

[...]

> @@ -1550,6 +1596,7 @@ BlockAIOCB *blk_aio_pwritev(BlockBackend *blk, int64_t offset,
>   
>   void blk_aio_cancel(BlockAIOCB *acb)
>   {
> +    assert(qemu_in_main_thread());
>       bdrv_aio_cancel(acb);
>   }
>   

This function is in block-backend-io.h, though.

[...]

> @@ -1879,7 +1936,6 @@ void blk_invalidate_cache(BlockBackend *blk, Error **errp)
>   bool blk_is_inserted(BlockBackend *blk)
>   {
>       BlockDriverState *bs = blk_bs(blk);
> -
>       return bs && bdrv_is_inserted(bs);
>   }

Seems like an unrelated hunk.

[...]

> @@ -2443,11 +2529,13 @@ int coroutine_fn blk_co_copy_range(BlockBackend *blk_in, int64_t off_in,

[…]

>   int blk_make_empty(BlockBackend *blk, Error **errp)
>   {
> +    assert(qemu_in_main_thread());
>       if (!blk_is_available(blk)) {
>           error_setg(errp, "No medium inserted");
>           return -ENOMEDIUM;

This function too is in block-backend-io.h.

Hanna

Emanuele Giuseppe Esposito Nov. 16, 2021, 10:15 a.m. UTC | #2

On 12/11/2021 12:01, Hanna Reitz wrote:
> On 25.10.21 12:17, Emanuele Giuseppe Esposito wrote:
>> All the global state (GS) API functions will check that
>> qemu_in_main_thread() returns true. If not, it means
>> that the safety of BQL cannot be guaranteed, and
>> they need to be moved to I/O.
>>
>> Signed-off-by: Emanuele Giuseppe Esposito <[e-mail]>
>> Reviewed-by: Stefan Hajnoczi <[e-mail]>
>> ---
>>   block/block-backend.c  | 90 +++++++++++++++++++++++++++++++++++++++++-
>>   softmmu/qdev-monitor.c |  2 +
>>   2 files changed, 91 insertions(+), 1 deletion(-)
>>
>> diff --git a/block/block-backend.c b/block/block-backend.c
>> index 0afc03fd66..ed45576007 100644
>> --- a/block/block-backend.c
>> +++ b/block/block-backend.c
> 
> [...]
> 
>> @@ -1550,6 +1596,7 @@ BlockAIOCB *blk_aio_pwritev(BlockBackend *blk, 
>> int64_t offset,
>>   void blk_aio_cancel(BlockAIOCB *acb)
>>   {
>> +    assert(qemu_in_main_thread());
>>       bdrv_aio_cancel(acb);
>>   }
> 
> This function is in block-backend-io.h, though.

I am confused a little on the {blk/bdrv}_aio functions, namely
blk_aio_cancel
bdrv_aio_cancel
blk_aio_cancel_async
bdrv_aio_cancel_async

Do you think they should be I/O? The assertion seems to hold though.

I agree with the rest of the comments.

Thank you,
Emanuele

Hanna Czenczek Nov. 16, 2021, 12:29 p.m. UTC | #3

On 16.11.21 11:15, Emanuele Giuseppe Esposito wrote:
>
>
> On 12/11/2021 12:01, Hanna Reitz wrote:
>> On 25.10.21 12:17, Emanuele Giuseppe Esposito wrote:
>>> All the global state (GS) API functions will check that
>>> qemu_in_main_thread() returns true. If not, it means
>>> that the safety of BQL cannot be guaranteed, and
>>> they need to be moved to I/O.
>>>
>>> Signed-off-by: Emanuele Giuseppe Esposito <[e-mail]>
>>> Reviewed-by: Stefan Hajnoczi <[e-mail]>
>>> ---
>>>   block/block-backend.c  | 90 
>>> +++++++++++++++++++++++++++++++++++++++++-
>>>   softmmu/qdev-monitor.c |  2 +
>>>   2 files changed, 91 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/block/block-backend.c b/block/block-backend.c
>>> index 0afc03fd66..ed45576007 100644
>>> --- a/block/block-backend.c
>>> +++ b/block/block-backend.c
>>
>> [...]
>>
>>> @@ -1550,6 +1596,7 @@ BlockAIOCB *blk_aio_pwritev(BlockBackend *blk, 
>>> int64_t offset,
>>>   void blk_aio_cancel(BlockAIOCB *acb)
>>>   {
>>> +    assert(qemu_in_main_thread());
>>>       bdrv_aio_cancel(acb);
>>>   }
>>
>> This function is in block-backend-io.h, though.
>
> I am confused a little on the {blk/bdrv}_aio functions, namely
> blk_aio_cancel
> bdrv_aio_cancel
> blk_aio_cancel_async
> bdrv_aio_cancel_async
>
> Do you think they should be I/O? The assertion seems to hold though.

Hm, semantically I would have classified them as I/O because they don’t 
modify state.  I don’t have a strong opinion, though, because they don’t 
actually do I/O.  They just cancel other I/O requests.

Most importantly though now I see there’s a comment in bdrv_aio_cancel() 
that states that “thread-safe code should use bdrv_aio_cancel_async 
exclusively”, which to me implies that bdrv_aio_cancel() (and 
blk_aio_cancel()) must be classified as GS, and it sounds like 
bdrv_aio_cancel_async() (and blk_aio_cancel_async()) should be 
classified as I/O.  Looking at the AIOCBInfo.cancel_async 
implementations (called by bdrv_aio_cancel_async()) I’m not sure they’re 
all really thread-safe, though...?  But at least bdrv_aio_cancel() 
claims they should be, so...

It seems to me like the intended separation is that bdrv_aio_cancel() 
should be GS and bdrv_aio_cancel_async() should be I/O.  I can’t verify 
that the .cancel_async implementations are really thread-safe, but 
neither can I verify that blk_aio_cancel_async() is only called by BQL 
callers.  That the assertions hold during testing isn’t too convincing 
for me, because we never wrote tests specifically to exercise these paths.

Hanna

Patch

diff --git a/block/block-backend.c b/block/block-backend.c
index 0afc03fd66..ed45576007 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -228,6 +228,7 @@  static void blk_root_activate(BdrvChild *child, Error **errp)
 
 void blk_set_force_allow_inactivate(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     blk->force_allow_inactivate = true;
 }
 
@@ -346,6 +347,8 @@  BlockBackend *blk_new(AioContext *ctx, uint64_t perm, uint64_t shared_perm)
 {
     BlockBackend *blk;
 
+    assert(qemu_in_main_thread());
+
     blk = g_new0(BlockBackend, 1);
     blk->refcnt = 1;
     blk->ctx = ctx;
@@ -383,6 +386,8 @@  BlockBackend *blk_new_with_bs(BlockDriverState *bs, uint64_t perm,
 {
     BlockBackend *blk = blk_new(bdrv_get_aio_context(bs), perm, shared_perm);
 
+    assert(qemu_in_main_thread());
+
     if (blk_insert_bs(blk, bs, errp) < 0) {
         blk_unref(blk);
         return NULL;
@@ -411,6 +416,8 @@  BlockBackend *blk_new_open(const char *filename, const char *reference,
     uint64_t perm = 0;
     uint64_t shared = BLK_PERM_ALL;
 
+    assert(qemu_in_main_thread());
+
     /*
      * blk_new_open() is mainly used in .bdrv_create implementations and the
      * tools where sharing isn't a major concern because the BDS stays private
@@ -488,6 +495,7 @@  static void drive_info_del(DriveInfo *dinfo)
 
 int blk_get_refcnt(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     return blk ? blk->refcnt : 0;
 }
 
@@ -498,6 +506,7 @@  int blk_get_refcnt(BlockBackend *blk)
 void blk_ref(BlockBackend *blk)
 {
     assert(blk->refcnt > 0);
+    assert(qemu_in_main_thread());
     blk->refcnt++;
 }
 
@@ -508,6 +517,7 @@  void blk_ref(BlockBackend *blk)
  */
 void blk_unref(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     if (blk) {
         assert(blk->refcnt > 0);
         if (blk->refcnt > 1) {
@@ -528,6 +538,7 @@  void blk_unref(BlockBackend *blk)
  */
 BlockBackend *blk_all_next(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     return blk ? QTAILQ_NEXT(blk, link)
                : QTAILQ_FIRST(&block_backends);
 }
@@ -536,6 +547,8 @@  void blk_remove_all_bs(void)
 {
     BlockBackend *blk = NULL;
 
+    assert(qemu_in_main_thread());
+
     while ((blk = blk_all_next(blk)) != NULL) {
         AioContext *ctx = blk_get_aio_context(blk);
 
@@ -559,6 +572,7 @@  void blk_remove_all_bs(void)
  */
 BlockBackend *blk_next(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     return blk ? QTAILQ_NEXT(blk, monitor_link)
                : QTAILQ_FIRST(&monitor_block_backends);
 }
@@ -625,6 +639,7 @@  static void bdrv_next_reset(BdrvNextIterator *it)
 
 BlockDriverState *bdrv_first(BdrvNextIterator *it)
 {
+    assert(qemu_in_main_thread());
     bdrv_next_reset(it);
     return bdrv_next(it);
 }
@@ -662,6 +677,7 @@  bool monitor_add_blk(BlockBackend *blk, const char *name, Error **errp)
 {
     assert(!blk->name);
     assert(name && name[0]);
+    assert(qemu_in_main_thread());
 
     if (!id_wellformed(name)) {
         error_setg(errp, "Invalid device name");
@@ -689,6 +705,8 @@  bool monitor_add_blk(BlockBackend *blk, const char *name, Error **errp)
  */
 void monitor_remove_blk(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
+
     if (!blk->name) {
         return;
     }
@@ -704,6 +722,7 @@  void monitor_remove_blk(BlockBackend *blk)
  */
 const char *blk_name(const BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     return blk->name ?: "";
 }
 
@@ -715,6 +734,7 @@  BlockBackend *blk_by_name(const char *name)
 {
     BlockBackend *blk = NULL;
 
+    assert(qemu_in_main_thread());
     assert(name);
     while ((blk = blk_next(blk)) != NULL) {
         if (!strcmp(name, blk->name)) {
@@ -749,6 +769,7 @@  static BlockBackend *bdrv_first_blk(BlockDriverState *bs)
  */
 bool bdrv_has_blk(BlockDriverState *bs)
 {
+    assert(qemu_in_main_thread());
     return bdrv_first_blk(bs) != NULL;
 }
 
@@ -759,6 +780,7 @@  bool bdrv_is_root_node(BlockDriverState *bs)
 {
     BdrvChild *c;
 
+    assert(qemu_in_main_thread());
     QLIST_FOREACH(c, &bs->parents, next_parent) {
         if (c->klass != &child_root) {
             return false;
@@ -808,6 +830,7 @@  BlockBackend *blk_by_legacy_dinfo(DriveInfo *dinfo)
  */
 BlockBackendPublic *blk_get_public(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     return &blk->public;
 }
 
@@ -816,6 +839,7 @@  BlockBackendPublic *blk_get_public(BlockBackend *blk)
  */
 BlockBackend *blk_by_public(BlockBackendPublic *public)
 {
+    assert(qemu_in_main_thread());
     return container_of(public, BlockBackend, public);
 }
 
@@ -828,6 +852,8 @@  void blk_remove_bs(BlockBackend *blk)
     BlockDriverState *bs;
     BdrvChild *root;
 
+    assert(qemu_in_main_thread());
+
     notifier_list_notify(&blk->remove_bs_notifiers, blk);
     if (tgm->throttle_state) {
         bs = blk_bs(blk);
@@ -855,6 +881,7 @@  void blk_remove_bs(BlockBackend *blk)
 int blk_insert_bs(BlockBackend *blk, BlockDriverState *bs, Error **errp)
 {
     ThrottleGroupMember *tgm = &blk->public.throttle_group_member;
+    assert(qemu_in_main_thread());
     bdrv_ref(bs);
     blk->root = bdrv_root_attach_child(bs, "root", &child_root,
                                        BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
@@ -889,6 +916,7 @@  int blk_set_perm(BlockBackend *blk, uint64_t perm, uint64_t shared_perm,
 {
     int ret;
 
+    assert(qemu_in_main_thread());
     if (blk->root && !blk->disable_perm) {
         ret = bdrv_child_try_set_perm(blk->root, perm, shared_perm, errp);
         if (ret < 0) {
@@ -904,6 +932,7 @@  int blk_set_perm(BlockBackend *blk, uint64_t perm, uint64_t shared_perm,
 
 void blk_get_perm(BlockBackend *blk, uint64_t *perm, uint64_t *shared_perm)
 {
+    assert(qemu_in_main_thread());
     *perm = blk->perm;
     *shared_perm = blk->shared_perm;
 }
@@ -914,6 +943,7 @@  void blk_get_perm(BlockBackend *blk, uint64_t *perm, uint64_t *shared_perm)
  */
 int blk_attach_dev(BlockBackend *blk, DeviceState *dev)
 {
+    assert(qemu_in_main_thread());
     if (blk->dev) {
         return -EBUSY;
     }
@@ -939,6 +969,7 @@  int blk_attach_dev(BlockBackend *blk, DeviceState *dev)
 void blk_detach_dev(BlockBackend *blk, DeviceState *dev)
 {
     assert(blk->dev == dev);
+    assert(qemu_in_main_thread());
     blk->dev = NULL;
     blk->dev_ops = NULL;
     blk->dev_opaque = NULL;
@@ -952,6 +983,7 @@  void blk_detach_dev(BlockBackend *blk, DeviceState *dev)
  */
 DeviceState *blk_get_attached_dev(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     return blk->dev;
 }
 
@@ -960,6 +992,7 @@  DeviceState *blk_get_attached_dev(BlockBackend *blk)
 char *blk_get_attached_dev_id(BlockBackend *blk)
 {
     DeviceState *dev = blk->dev;
+    assert(qemu_in_main_thread());
 
     if (!dev) {
         return g_strdup("");
@@ -980,6 +1013,8 @@  BlockBackend *blk_by_dev(void *dev)
 {
     BlockBackend *blk = NULL;
 
+    assert(qemu_in_main_thread());
+
     assert(dev != NULL);
     while ((blk = blk_all_next(blk)) != NULL) {
         if (blk->dev == dev) {
@@ -997,6 +1032,7 @@  BlockBackend *blk_by_dev(void *dev)
 void blk_set_dev_ops(BlockBackend *blk, const BlockDevOps *ops,
                      void *opaque)
 {
+    assert(qemu_in_main_thread());
     blk->dev_ops = ops;
     blk->dev_opaque = opaque;
 
@@ -1018,6 +1054,7 @@  void blk_set_dev_ops(BlockBackend *blk, const BlockDevOps *ops,
  */
 void blk_dev_change_media_cb(BlockBackend *blk, bool load, Error **errp)
 {
+    assert(qemu_in_main_thread());
     if (blk->dev_ops && blk->dev_ops->change_media_cb) {
         bool tray_was_open, tray_is_open;
         Error *local_err = NULL;
@@ -1109,6 +1146,7 @@  static void blk_root_resize(BdrvChild *child)
 
 void blk_iostatus_enable(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     blk->iostatus_enabled = true;
     blk->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
 }
@@ -1117,6 +1155,7 @@  void blk_iostatus_enable(BlockBackend *blk)
  * enables it _and_ the VM is configured to stop on errors */
 bool blk_iostatus_is_enabled(const BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     return (blk->iostatus_enabled &&
            (blk->on_write_error == BLOCKDEV_ON_ERROR_ENOSPC ||
             blk->on_write_error == BLOCKDEV_ON_ERROR_STOP   ||
@@ -1125,16 +1164,19 @@  bool blk_iostatus_is_enabled(const BlockBackend *blk)
 
 BlockDeviceIoStatus blk_iostatus(const BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     return blk->iostatus;
 }
 
 void blk_iostatus_disable(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     blk->iostatus_enabled = false;
 }
 
 void blk_iostatus_reset(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     if (blk_iostatus_is_enabled(blk)) {
         blk->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
     }
@@ -1142,6 +1184,7 @@  void blk_iostatus_reset(BlockBackend *blk)
 
 void blk_iostatus_set_err(BlockBackend *blk, int error)
 {
+    assert(qemu_in_main_thread());
     assert(blk_iostatus_is_enabled(blk));
     if (blk->iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
         blk->iostatus = error == ENOSPC ? BLOCK_DEVICE_IO_STATUS_NOSPACE :
@@ -1341,6 +1384,7 @@  int blk_pwrite_zeroes(BlockBackend *blk, int64_t offset,
 
 int blk_make_zero(BlockBackend *blk, BdrvRequestFlags flags)
 {
+    assert(qemu_in_main_thread());
     return bdrv_make_zero(blk->root, flags);
 }
 
@@ -1369,6 +1413,7 @@  BlockAIOCB *blk_abort_aio_request(BlockBackend *blk,
                                   void *opaque, int ret)
 {
     struct BlockBackendAIOCB *acb;
+    assert(qemu_in_main_thread());
 
     blk_inc_in_flight(blk);
     acb = blk_aio_get(&block_backend_aiocb_info, blk, cb, opaque);
@@ -1523,6 +1568,7 @@  void blk_get_geometry(BlockBackend *blk, uint64_t *nb_sectors_ptr)
 
 int64_t blk_nb_sectors(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     if (!blk_is_available(blk)) {
         return -ENOMEDIUM;
     }
@@ -1550,6 +1596,7 @@  BlockAIOCB *blk_aio_pwritev(BlockBackend *blk, int64_t offset,
 
 void blk_aio_cancel(BlockAIOCB *acb)
 {
+    assert(qemu_in_main_thread());
     bdrv_aio_cancel(acb);
 }
 
@@ -1707,6 +1754,8 @@  void blk_drain(BlockBackend *blk)
 {
     BlockDriverState *bs = blk_bs(blk);
 
+    assert(qemu_in_main_thread());
+
     if (bs) {
         bdrv_drained_begin(bs);
     }
@@ -1724,6 +1773,8 @@  void blk_drain_all(void)
 {
     BlockBackend *blk = NULL;
 
+    assert(qemu_in_main_thread());
+
     bdrv_drain_all_begin();
 
     while ((blk = blk_all_next(blk)) != NULL) {
@@ -1743,6 +1794,7 @@  void blk_drain_all(void)
 void blk_set_on_error(BlockBackend *blk, BlockdevOnError on_read_error,
                       BlockdevOnError on_write_error)
 {
+    assert(qemu_in_main_thread());
     blk->on_read_error = on_read_error;
     blk->on_write_error = on_write_error;
 }
@@ -1826,6 +1878,7 @@  void blk_error_action(BlockBackend *blk, BlockErrorAction action,
 bool blk_supports_write_perm(BlockBackend *blk)
 {
     BlockDriverState *bs = blk_bs(blk);
+    assert(qemu_in_main_thread());
 
     if (bs) {
         return !bdrv_is_read_only(bs);
@@ -1846,6 +1899,7 @@  bool blk_is_writable(BlockBackend *blk)
 bool blk_is_sg(BlockBackend *blk)
 {
     BlockDriverState *bs = blk_bs(blk);
+    assert(qemu_in_main_thread());
 
     if (!bs) {
         return false;
@@ -1856,17 +1910,20 @@  bool blk_is_sg(BlockBackend *blk)
 
 bool blk_enable_write_cache(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     return blk->enable_write_cache;
 }
 
 void blk_set_enable_write_cache(BlockBackend *blk, bool wce)
 {
+    assert(qemu_in_main_thread());
     blk->enable_write_cache = wce;
 }
 
 void blk_invalidate_cache(BlockBackend *blk, Error **errp)
 {
     BlockDriverState *bs = blk_bs(blk);
+    assert(qemu_in_main_thread());
 
     if (!bs) {
         error_setg(errp, "Device '%s' has no medium", blk->name);
@@ -1879,7 +1936,6 @@  void blk_invalidate_cache(BlockBackend *blk, Error **errp)
 bool blk_is_inserted(BlockBackend *blk)
 {
     BlockDriverState *bs = blk_bs(blk);
-
     return bs && bdrv_is_inserted(bs);
 }
 
@@ -1891,6 +1947,7 @@  bool blk_is_available(BlockBackend *blk)
 void blk_lock_medium(BlockBackend *blk, bool locked)
 {
     BlockDriverState *bs = blk_bs(blk);
+    assert(qemu_in_main_thread());
 
     if (bs) {
         bdrv_lock_medium(bs, locked);
@@ -1900,6 +1957,8 @@  void blk_lock_medium(BlockBackend *blk, bool locked)
 void blk_eject(BlockBackend *blk, bool eject_flag)
 {
     BlockDriverState *bs = blk_bs(blk);
+    assert(qemu_in_main_thread());
+
     char *id;
 
     if (bs) {
@@ -1917,6 +1976,7 @@  void blk_eject(BlockBackend *blk, bool eject_flag)
 int blk_get_flags(BlockBackend *blk)
 {
     BlockDriverState *bs = blk_bs(blk);
+    assert(qemu_in_main_thread());
 
     if (bs) {
         return bdrv_get_flags(bs);
@@ -1970,6 +2030,7 @@  int blk_get_max_iov(BlockBackend *blk)
 
 void blk_set_guest_block_size(BlockBackend *blk, int align)
 {
+    assert(qemu_in_main_thread());
     blk->guest_block_size = align;
 }
 
@@ -1986,6 +2047,7 @@  void *blk_blockalign(BlockBackend *blk, size_t size)
 bool blk_op_is_blocked(BlockBackend *blk, BlockOpType op, Error **errp)
 {
     BlockDriverState *bs = blk_bs(blk);
+    assert(qemu_in_main_thread());
 
     if (!bs) {
         return false;
@@ -1997,6 +2059,7 @@  bool blk_op_is_blocked(BlockBackend *blk, BlockOpType op, Error **errp)
 void blk_op_unblock(BlockBackend *blk, BlockOpType op, Error *reason)
 {
     BlockDriverState *bs = blk_bs(blk);
+    assert(qemu_in_main_thread());
 
     if (bs) {
         bdrv_op_unblock(bs, op, reason);
@@ -2006,6 +2069,7 @@  void blk_op_unblock(BlockBackend *blk, BlockOpType op, Error *reason)
 void blk_op_block_all(BlockBackend *blk, Error *reason)
 {
     BlockDriverState *bs = blk_bs(blk);
+    assert(qemu_in_main_thread());
 
     if (bs) {
         bdrv_op_block_all(bs, reason);
@@ -2015,6 +2079,7 @@  void blk_op_block_all(BlockBackend *blk, Error *reason)
 void blk_op_unblock_all(BlockBackend *blk, Error *reason)
 {
     BlockDriverState *bs = blk_bs(blk);
+    assert(qemu_in_main_thread());
 
     if (bs) {
         bdrv_op_unblock_all(bs, reason);
@@ -2069,6 +2134,7 @@  static int blk_do_set_aio_context(BlockBackend *blk, AioContext *new_context,
 int blk_set_aio_context(BlockBackend *blk, AioContext *new_context,
                         Error **errp)
 {
+    assert(qemu_in_main_thread());
     return blk_do_set_aio_context(blk, new_context, true, errp);
 }
 
@@ -2105,6 +2171,7 @@  void blk_add_aio_context_notifier(BlockBackend *blk,
 {
     BlockBackendAioNotifier *notifier;
     BlockDriverState *bs = blk_bs(blk);
+    assert(qemu_in_main_thread());
 
     notifier = g_new(BlockBackendAioNotifier, 1);
     notifier->attached_aio_context = attached_aio_context;
@@ -2127,6 +2194,8 @@  void blk_remove_aio_context_notifier(BlockBackend *blk,
     BlockBackendAioNotifier *notifier;
     BlockDriverState *bs = blk_bs(blk);
 
+    assert(qemu_in_main_thread());
+
     if (bs) {
         bdrv_remove_aio_context_notifier(bs, attached_aio_context,
                                          detach_aio_context, opaque);
@@ -2147,11 +2216,13 @@  void blk_remove_aio_context_notifier(BlockBackend *blk,
 
 void blk_add_remove_bs_notifier(BlockBackend *blk, Notifier *notify)
 {
+    assert(qemu_in_main_thread());
     notifier_list_add(&blk->remove_bs_notifiers, notify);
 }
 
 void blk_add_insert_bs_notifier(BlockBackend *blk, Notifier *notify)
 {
+    assert(qemu_in_main_thread());
     notifier_list_add(&blk->insert_bs_notifiers, notify);
 }
 
@@ -2214,6 +2285,7 @@  int blk_save_vmstate(BlockBackend *blk, const uint8_t *buf,
                      int64_t pos, int size)
 {
     int ret;
+    assert(qemu_in_main_thread());
 
     if (!blk_is_available(blk)) {
         return -ENOMEDIUM;
@@ -2233,6 +2305,7 @@  int blk_save_vmstate(BlockBackend *blk, const uint8_t *buf,
 
 int blk_load_vmstate(BlockBackend *blk, uint8_t *buf, int64_t pos, int size)
 {
+    assert(qemu_in_main_thread());
     if (!blk_is_available(blk)) {
         return -ENOMEDIUM;
     }
@@ -2242,6 +2315,7 @@  int blk_load_vmstate(BlockBackend *blk, uint8_t *buf, int64_t pos, int size)
 
 int blk_probe_blocksizes(BlockBackend *blk, BlockSizes *bsz)
 {
+    assert(qemu_in_main_thread());
     if (!blk_is_available(blk)) {
         return -ENOMEDIUM;
     }
@@ -2251,6 +2325,7 @@  int blk_probe_blocksizes(BlockBackend *blk, BlockSizes *bsz)
 
 int blk_probe_geometry(BlockBackend *blk, HDGeometry *geo)
 {
+    assert(qemu_in_main_thread());
     if (!blk_is_available(blk)) {
         return -ENOMEDIUM;
     }
@@ -2264,6 +2339,7 @@  int blk_probe_geometry(BlockBackend *blk, HDGeometry *geo)
  */
 void blk_update_root_state(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     assert(blk->root);
 
     blk->root_state.open_flags    = blk->root->bs->open_flags;
@@ -2276,6 +2352,7 @@  void blk_update_root_state(BlockBackend *blk)
  */
 bool blk_get_detect_zeroes_from_root_state(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     return blk->root_state.detect_zeroes;
 }
 
@@ -2285,17 +2362,20 @@  bool blk_get_detect_zeroes_from_root_state(BlockBackend *blk)
  */
 int blk_get_open_flags_from_root_state(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     return blk->root_state.open_flags;
 }
 
 BlockBackendRootState *blk_get_root_state(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     return &blk->root_state;
 }
 
 int blk_commit_all(void)
 {
     BlockBackend *blk = NULL;
+    assert(qemu_in_main_thread());
 
     while ((blk = blk_all_next(blk)) != NULL) {
         AioContext *aio_context = blk_get_aio_context(blk);
@@ -2320,6 +2400,7 @@  int blk_commit_all(void)
 /* throttling disk I/O limits */
 void blk_set_io_limits(BlockBackend *blk, ThrottleConfig *cfg)
 {
+    assert(qemu_in_main_thread());
     throttle_group_config(&blk->public.throttle_group_member, cfg);
 }
 
@@ -2328,6 +2409,7 @@  void blk_io_limits_disable(BlockBackend *blk)
     BlockDriverState *bs = blk_bs(blk);
     ThrottleGroupMember *tgm = &blk->public.throttle_group_member;
     assert(tgm->throttle_state);
+    assert(qemu_in_main_thread());
     if (bs) {
         bdrv_drained_begin(bs);
     }
@@ -2341,12 +2423,14 @@  void blk_io_limits_disable(BlockBackend *blk)
 void blk_io_limits_enable(BlockBackend *blk, const char *group)
 {
     assert(!blk->public.throttle_group_member.throttle_state);
+    assert(qemu_in_main_thread());
     throttle_group_register_tgm(&blk->public.throttle_group_member,
                                 group, blk_get_aio_context(blk));
 }
 
 void blk_io_limits_update_group(BlockBackend *blk, const char *group)
 {
+    assert(qemu_in_main_thread());
     /* this BB is not part of any group */
     if (!blk->public.throttle_group_member.throttle_state) {
         return;
@@ -2414,11 +2498,13 @@  static void blk_root_drained_end(BdrvChild *child, int *drained_end_counter)
 
 void blk_register_buf(BlockBackend *blk, void *host, size_t size)
 {
+    assert(qemu_in_main_thread());
     bdrv_register_buf(blk_bs(blk), host, size);
 }
 
 void blk_unregister_buf(BlockBackend *blk, void *host)
 {
+    assert(qemu_in_main_thread());
     bdrv_unregister_buf(blk_bs(blk), host);
 }
 
@@ -2443,11 +2529,13 @@  int coroutine_fn blk_co_copy_range(BlockBackend *blk_in, int64_t off_in,
 
 const BdrvChild *blk_root(BlockBackend *blk)
 {
+    assert(qemu_in_main_thread());
     return blk->root;
 }
 
 int blk_make_empty(BlockBackend *blk, Error **errp)
 {
+    assert(qemu_in_main_thread());
     if (!blk_is_available(blk)) {
         error_setg(errp, "No medium inserted");
         return -ENOMEDIUM;
diff --git a/softmmu/qdev-monitor.c b/softmmu/qdev-monitor.c
index 4851de51a5..71cb6a549b 100644
--- a/softmmu/qdev-monitor.c
+++ b/softmmu/qdev-monitor.c
@@ -963,6 +963,8 @@  BlockBackend *blk_by_qdev_id(const char *id, Error **errp)
     DeviceState *dev;
     BlockBackend *blk;
 
+    assert(qemu_in_main_thread());
+
     dev = find_device_state(id, errp);
     if (dev == NULL) {
         return NULL;