[PATCH v2] migration/colo: Fix bdrv_graph_rdlock_main_loop: Assertion `!qemu_in_coroutine()' failed.

[PATCH v2] migration/colo: Fix bdrv_graph_rdlock_main_loop: Assertion `!qemu_in_coroutine()' failed.

[Li Zhijian via]

bdrv_activate_all() should not be called from the coroutine context, move
it to the QEMU thread colo_process_incoming_thread() with the bql_lock
protected.

The backtrace is as follows:
 #4  0x0000561af7948362 in bdrv_graph_rdlock_main_loop () at ../block/graph-lock.c:260
 #5  0x0000561af7907a68 in graph_lockable_auto_lock_mainloop (x=0x7fd29810be7b) at /patch/to/qemu/include/block/graph-lock.h:259
 #6  0x0000561af79167d1 in bdrv_activate_all (errp=0x7fd29810bed0) at ../block.c:6906
 #7  0x0000561af762b4af in colo_incoming_co () at ../migration/colo.c:935
 #8  0x0000561af7607e57 in process_incoming_migration_co (opaque=0x0) at ../migration/migration.c:793
 #9  0x0000561af7adbeeb in coroutine_trampoline (i0=-106876144, i1=22042) at ../util/coroutine-ucontext.c:175
 #10 0x00007fd2a5cf21c0 in  () at /lib64/libc.so.6

CC: Fabiano Rosas <farosas@suse.de>
Closes: https://gitlab.com/qemu-project/qemu/-/issues/2277
Fixes: 2b3912f135 ("block: Mark bdrv_first_blk() and bdrv_is_root_node() GRAPH_RDLOCK")
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
---
V2: fix missing bql_unlock() in error path.
---
 migration/colo.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/migration/colo.c b/migration/colo.c
index 84632a603e..5600a43d78 100644
--- a/migration/colo.c
+++ b/migration/colo.c
@@ -835,6 +835,16 @@ static void *colo_process_incoming_thread(void *opaque)
         return NULL;
     }
 
+    /* Make sure all file formats throw away their mutable metadata */
+    bql_lock();
+    bdrv_activate_all(&local_err);
+    if (local_err) {
+        bql_unlock();
+        error_report_err(local_err);
+        return NULL;
+    }
+    bql_unlock();
+
     failover_init_state();
 
     mis->to_src_file = qemu_file_get_return_path(mis->from_src_file);
@@ -922,7 +932,6 @@ out:
 int coroutine_fn colo_incoming_co(void)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
-    Error *local_err = NULL;
     QemuThread th;
 
     assert(bql_locked());
@@ -931,13 +940,6 @@ int coroutine_fn colo_incoming_co(void)
         return 0;
     }
 
-    /* Make sure all file formats throw away their mutable metadata */
-    bdrv_activate_all(&local_err);
-    if (local_err) {
-        error_report_err(local_err);
-        return -EINVAL;
-    }
-
     qemu_thread_create(&th, "COLO incoming", colo_process_incoming_thread,
                        mis, QEMU_THREAD_JOINABLE);
 
-- 
2.31.1

Re: [PATCH v2] migration/colo: Fix bdrv_graph_rdlock_main_loop: Assertion `!qemu_in_coroutine()' failed.

[Philippe Mathieu-Daudé]

On 17/4/24 04:56, Li Zhijian via wrote:
> bdrv_activate_all() should not be called from the coroutine context, move
> it to the QEMU thread colo_process_incoming_thread() with the bql_lock
> protected.
> 
> The backtrace is as follows:
>   #4  0x0000561af7948362 in bdrv_graph_rdlock_main_loop () at ../block/graph-lock.c:260
>   #5  0x0000561af7907a68 in graph_lockable_auto_lock_mainloop (x=0x7fd29810be7b) at /patch/to/qemu/include/block/graph-lock.h:259
>   #6  0x0000561af79167d1 in bdrv_activate_all (errp=0x7fd29810bed0) at ../block.c:6906
>   #7  0x0000561af762b4af in colo_incoming_co () at ../migration/colo.c:935
>   #8  0x0000561af7607e57 in process_incoming_migration_co (opaque=0x0) at ../migration/migration.c:793
>   #9  0x0000561af7adbeeb in coroutine_trampoline (i0=-106876144, i1=22042) at ../util/coroutine-ucontext.c:175
>   #10 0x00007fd2a5cf21c0 in  () at /lib64/libc.so.6
> 
> CC: Fabiano Rosas <farosas@suse.de>

Cc: qemu-stable@nongnu.org

> Closes: https://gitlab.com/qemu-project/qemu/-/issues/2277
> Fixes: 2b3912f135 ("block: Mark bdrv_first_blk() and bdrv_is_root_node() GRAPH_RDLOCK")
> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
> ---
> V2: fix missing bql_unlock() in error path.
> ---
>   migration/colo.c | 18 ++++++++++--------
>   1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/migration/colo.c b/migration/colo.c
> index 84632a603e..5600a43d78 100644
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -835,6 +835,16 @@ static void *colo_process_incoming_thread(void *opaque)
>           return NULL;
>       }
>   
> +    /* Make sure all file formats throw away their mutable metadata */
> +    bql_lock();

Note there is also the convenient BQL_LOCK_GUARD() macro.

> +    bdrv_activate_all(&local_err);
> +    if (local_err) {
> +        bql_unlock();
> +        error_report_err(local_err);
> +        return NULL;
> +    }
> +    bql_unlock();
> +
>       failover_init_state();

RE: [PATCH v2] migration/colo: Fix bdrv_graph_rdlock_main_loop: Assertion `!qemu_in_coroutine()' failed.

[Zhang, Chen]

> -----Original Message-----
> From: Philippe Mathieu-Daudé <philmd@linaro.org>
> Sent: Wednesday, April 17, 2024 2:14 PM
> To: Li Zhijian <lizhijian@fujitsu.com>; Zhang, Hailiang
> <zhanghailiang@xfusion.com>; peterx@redhat.com; farosas@suse.de
> Cc: qemu-devel@nongnu.org; Zhang, Chen <chen.zhang@intel.com>; Wen
> Congyang <wencongyang2@huawei.com>; Xie Changlong
> <xiechanglong.d@gmail.com>
> Subject: Re: [PATCH v2] migration/colo: Fix bdrv_graph_rdlock_main_loop:
> Assertion `!qemu_in_coroutine()' failed.
> 
> On 17/4/24 04:56, Li Zhijian via wrote:
> > bdrv_activate_all() should not be called from the coroutine context,
> > move it to the QEMU thread colo_process_incoming_thread() with the
> > bql_lock protected.
> >
> > The backtrace is as follows:
> >   #4  0x0000561af7948362 in bdrv_graph_rdlock_main_loop ()
> at ../block/graph-lock.c:260
> >   #5  0x0000561af7907a68 in graph_lockable_auto_lock_mainloop
> (x=0x7fd29810be7b) at /patch/to/qemu/include/block/graph-lock.h:259
> >   #6  0x0000561af79167d1 in bdrv_activate_all (errp=0x7fd29810bed0)
> at ../block.c:6906
> >   #7  0x0000561af762b4af in colo_incoming_co () at ../migration/colo.c:935
> >   #8  0x0000561af7607e57 in process_incoming_migration_co (opaque=0x0)
> at ../migration/migration.c:793
> >   #9  0x0000561af7adbeeb in coroutine_trampoline (i0=-106876144,
> i1=22042) at ../util/coroutine-ucontext.c:175
> >   #10 0x00007fd2a5cf21c0 in  () at /lib64/libc.so.6
> >
> > CC: Fabiano Rosas <farosas@suse.de>
> 
> Cc: qemu-stable@nongnu.org
> 
> > Closes: https://gitlab.com/qemu-project/qemu/-/issues/2277
> > Fixes: 2b3912f135 ("block: Mark bdrv_first_blk() and
> > bdrv_is_root_node() GRAPH_RDLOCK")
> > Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>

It looks good to me. And already verified this patch in my environment.
After address Phillippe's comments please add:

Reviewed-by: Zhang Chen <chen.zhang@intel.com>
Tested-by: Zhang Chen <chen.zhang@intel.com>

Thanks
Chen

> > ---
> > V2: fix missing bql_unlock() in error path.
> > ---
> >   migration/colo.c | 18 ++++++++++--------
> >   1 file changed, 10 insertions(+), 8 deletions(-)
> >
> > diff --git a/migration/colo.c b/migration/colo.c index
> > 84632a603e..5600a43d78 100644
> > --- a/migration/colo.c
> > +++ b/migration/colo.c
> > @@ -835,6 +835,16 @@ static void *colo_process_incoming_thread(void
> *opaque)
> >           return NULL;
> >       }
> >
> > +    /* Make sure all file formats throw away their mutable metadata */
> > +    bql_lock();
> 
> Note there is also the convenient BQL_LOCK_GUARD() macro.
> 
> > +    bdrv_activate_all(&local_err);
> > +    if (local_err) {
> > +        bql_unlock();
> > +        error_report_err(local_err);
> > +        return NULL;
> > +    }
> > +    bql_unlock();
> > +
> >       failover_init_state();

Re: [PATCH v2] migration/colo: Fix bdrv_graph_rdlock_main_loop: Assertion `!qemu_in_coroutine()' failed.

[Philippe Mathieu-Daudé]

On 17/4/24 08:47, Zhang, Chen wrote:
> 
> 
>> -----Original Message-----
>> From: Philippe Mathieu-Daudé <philmd@linaro.org>
>> Sent: Wednesday, April 17, 2024 2:14 PM
>> To: Li Zhijian <lizhijian@fujitsu.com>; Zhang, Hailiang
>> <zhanghailiang@xfusion.com>; peterx@redhat.com; farosas@suse.de
>> Cc: qemu-devel@nongnu.org; Zhang, Chen <chen.zhang@intel.com>; Wen
>> Congyang <wencongyang2@huawei.com>; Xie Changlong
>> <xiechanglong.d@gmail.com>
>> Subject: Re: [PATCH v2] migration/colo: Fix bdrv_graph_rdlock_main_loop:
>> Assertion `!qemu_in_coroutine()' failed.
>>
>> On 17/4/24 04:56, Li Zhijian via wrote:
>>> bdrv_activate_all() should not be called from the coroutine context,
>>> move it to the QEMU thread colo_process_incoming_thread() with the
>>> bql_lock protected.
>>>
>>> The backtrace is as follows:
>>>    #4  0x0000561af7948362 in bdrv_graph_rdlock_main_loop ()
>> at ../block/graph-lock.c:260
>>>    #5  0x0000561af7907a68 in graph_lockable_auto_lock_mainloop
>> (x=0x7fd29810be7b) at /patch/to/qemu/include/block/graph-lock.h:259
>>>    #6  0x0000561af79167d1 in bdrv_activate_all (errp=0x7fd29810bed0)
>> at ../block.c:6906
>>>    #7  0x0000561af762b4af in colo_incoming_co () at ../migration/colo.c:935
>>>    #8  0x0000561af7607e57 in process_incoming_migration_co (opaque=0x0)
>> at ../migration/migration.c:793
>>>    #9  0x0000561af7adbeeb in coroutine_trampoline (i0=-106876144,
>> i1=22042) at ../util/coroutine-ucontext.c:175
>>>    #10 0x00007fd2a5cf21c0 in  () at /lib64/libc.so.6
>>>
>>> CC: Fabiano Rosas <farosas@suse.de>
>>
>> Cc: qemu-stable@nongnu.org
>>
>>> Closes: https://gitlab.com/qemu-project/qemu/-/issues/2277
>>> Fixes: 2b3912f135 ("block: Mark bdrv_first_blk() and
>>> bdrv_is_root_node() GRAPH_RDLOCK")
>>> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
> 
> It looks good to me. And already verified this patch in my environment.
> After address Phillippe's comments

(I'm only suggesting, in case using the macro results in code
more easily maintainable)

> please add:
> 
> Reviewed-by: Zhang Chen <chen.zhang@intel.com>
> Tested-by: Zhang Chen <chen.zhang@intel.com>
> 
> Thanks
> Chen
> 
>>> ---
>>> V2: fix missing bql_unlock() in error path.
>>> ---
>>>    migration/colo.c | 18 ++++++++++--------
>>>    1 file changed, 10 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/migration/colo.c b/migration/colo.c index
>>> 84632a603e..5600a43d78 100644
>>> --- a/migration/colo.c
>>> +++ b/migration/colo.c
>>> @@ -835,6 +835,16 @@ static void *colo_process_incoming_thread(void
>> *opaque)
>>>            return NULL;
>>>        }
>>>
>>> +    /* Make sure all file formats throw away their mutable metadata */
>>> +    bql_lock();
>>
>> Note there is also the convenient BQL_LOCK_GUARD() macro.
>>
>>> +    bdrv_activate_all(&local_err);
>>> +    if (local_err) {
>>> +        bql_unlock();
>>> +        error_report_err(local_err);
>>> +        return NULL;
>>> +    }
>>> +    bql_unlock();
>>> +
>>>        failover_init_state();
> 

Re: [PATCH v2] migration/colo: Fix bdrv_graph_rdlock_main_loop: Assertion `!qemu_in_coroutine()' failed.

[Zhijian Li (Fujitsu) via]

On 17/04/2024 14:13, Philippe Mathieu-Daudé wrote:
> On 17/4/24 04:56, Li Zhijian via wrote:
>> bdrv_activate_all() should not be called from the coroutine context, move
>> it to the QEMU thread colo_process_incoming_thread() with the bql_lock
>> protected.
>>
>> The backtrace is as follows:
>>   #4  0x0000561af7948362 in bdrv_graph_rdlock_main_loop () at ../block/graph-lock.c:260
>>   #5  0x0000561af7907a68 in graph_lockable_auto_lock_mainloop (x=0x7fd29810be7b) at /patch/to/qemu/include/block/graph-lock.h:259
>>   #6  0x0000561af79167d1 in bdrv_activate_all (errp=0x7fd29810bed0) at ../block.c:6906
>>   #7  0x0000561af762b4af in colo_incoming_co () at ../migration/colo.c:935
>>   #8  0x0000561af7607e57 in process_incoming_migration_co (opaque=0x0) at ../migration/migration.c:793
>>   #9  0x0000561af7adbeeb in coroutine_trampoline (i0=-106876144, i1=22042) at ../util/coroutine-ucontext.c:175
>>   #10 0x00007fd2a5cf21c0 in  () at /lib64/libc.so.6
>>
>> CC: Fabiano Rosas <farosas@suse.de>
> 
> Cc: qemu-stable@nongnu.org
> 
>> Closes: https://gitlab.com/qemu-project/qemu/-/issues/2277
>> Fixes: 2b3912f135 ("block: Mark bdrv_first_blk() and bdrv_is_root_node() GRAPH_RDLOCK")
>> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
>> ---
>> V2: fix missing bql_unlock() in error path.
>> ---
>>   migration/colo.c | 18 ++++++++++--------
>>   1 file changed, 10 insertions(+), 8 deletions(-)
>>
>> diff --git a/migration/colo.c b/migration/colo.c
>> index 84632a603e..5600a43d78 100644
>> --- a/migration/colo.c
>> +++ b/migration/colo.c
>> @@ -835,6 +835,16 @@ static void *colo_process_incoming_thread(void *opaque)
>>           return NULL;
>>       }
>> +    /* Make sure all file formats throw away their mutable metadata */
>> +    bql_lock();
> 
> Note there is also the convenient BQL_LOCK_GUARD() macro.

Thanks for your reminder, Philippe.

IIUC, BQL_LOCK_GUARD() will lock all the rest code till the subroutine ends.
So it's not suitable for this case where we only need a partial critical section.


Thanks
Zhijian


> 
>> +    bdrv_activate_all(&local_err);
>> +    if (local_err) {
>> +        bql_unlock();
>> +        error_report_err(local_err);
>> +        return NULL;
>> +    }
>> +    bql_unlock();
>> +
>>       failover_init_state();
> 

Re: [PATCH v2] migration/colo: Fix bdrv_graph_rdlock_main_loop: Assertion `!qemu_in_coroutine()' failed.

[Fabiano Rosas]

Li Zhijian via <qemu-devel@nongnu.org> writes:

> bdrv_activate_all() should not be called from the coroutine context, move
> it to the QEMU thread colo_process_incoming_thread() with the bql_lock
> protected.
>
> The backtrace is as follows:
>  #4  0x0000561af7948362 in bdrv_graph_rdlock_main_loop () at ../block/graph-lock.c:260
>  #5  0x0000561af7907a68 in graph_lockable_auto_lock_mainloop (x=0x7fd29810be7b) at /patch/to/qemu/include/block/graph-lock.h:259
>  #6  0x0000561af79167d1 in bdrv_activate_all (errp=0x7fd29810bed0) at ../block.c:6906
>  #7  0x0000561af762b4af in colo_incoming_co () at ../migration/colo.c:935
>  #8  0x0000561af7607e57 in process_incoming_migration_co (opaque=0x0) at ../migration/migration.c:793
>  #9  0x0000561af7adbeeb in coroutine_trampoline (i0=-106876144, i1=22042) at ../util/coroutine-ucontext.c:175
>  #10 0x00007fd2a5cf21c0 in  () at /lib64/libc.so.6
>
> CC: Fabiano Rosas <farosas@suse.de>
> Closes: https://gitlab.com/qemu-project/qemu/-/issues/2277
> Fixes: 2b3912f135 ("block: Mark bdrv_first_blk() and bdrv_is_root_node() GRAPH_RDLOCK")
> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>

Reviewed-by: Fabiano Rosas <farosas@suse.de>

Re: [PATCH v2] migration/colo: Fix bdrv_graph_rdlock_main_loop: Assertion `!qemu_in_coroutine()' failed.

[Peter Xu]

On Wed, Apr 17, 2024 at 10:56:34AM +0800, Li Zhijian via wrote:
> bdrv_activate_all() should not be called from the coroutine context, move
> it to the QEMU thread colo_process_incoming_thread() with the bql_lock
> protected.
> 
> The backtrace is as follows:
>  #4  0x0000561af7948362 in bdrv_graph_rdlock_main_loop () at ../block/graph-lock.c:260
>  #5  0x0000561af7907a68 in graph_lockable_auto_lock_mainloop (x=0x7fd29810be7b) at /patch/to/qemu/include/block/graph-lock.h:259
>  #6  0x0000561af79167d1 in bdrv_activate_all (errp=0x7fd29810bed0) at ../block.c:6906
>  #7  0x0000561af762b4af in colo_incoming_co () at ../migration/colo.c:935
>  #8  0x0000561af7607e57 in process_incoming_migration_co (opaque=0x0) at ../migration/migration.c:793
>  #9  0x0000561af7adbeeb in coroutine_trampoline (i0=-106876144, i1=22042) at ../util/coroutine-ucontext.c:175
>  #10 0x00007fd2a5cf21c0 in  () at /lib64/libc.so.6
> 
> CC: Fabiano Rosas <farosas@suse.de>
> Closes: https://gitlab.com/qemu-project/qemu/-/issues/2277
> Fixes: 2b3912f135 ("block: Mark bdrv_first_blk() and bdrv_is_root_node() GRAPH_RDLOCK")
> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>

queued (and cc stable), thanks.

-- 
Peter Xu

Re: [PATCH v2] migration/colo: Fix bdrv_graph_rdlock_main_loop: Assertion `!qemu_in_coroutine()' failed.

[Michael Tokarev]

17.04.2024 05:56, Li Zhijian via wrote:
> bdrv_activate_all() should not be called from the coroutine context, move
> it to the QEMU thread colo_process_incoming_thread() with the bql_lock
> protected.
> 
> The backtrace is as follows:
>   #4  0x0000561af7948362 in bdrv_graph_rdlock_main_loop () at ../block/graph-lock.c:260
>   #5  0x0000561af7907a68 in graph_lockable_auto_lock_mainloop (x=0x7fd29810be7b) at /patch/to/qemu/include/block/graph-lock.h:259
>   #6  0x0000561af79167d1 in bdrv_activate_all (errp=0x7fd29810bed0) at ../block.c:6906
>   #7  0x0000561af762b4af in colo_incoming_co () at ../migration/colo.c:935
>   #8  0x0000561af7607e57 in process_incoming_migration_co (opaque=0x0) at ../migration/migration.c:793
>   #9  0x0000561af7adbeeb in coroutine_trampoline (i0=-106876144, i1=22042) at ../util/coroutine-ucontext.c:175
>   #10 0x00007fd2a5cf21c0 in  () at /lib64/libc.so.6
> 
> CC: Fabiano Rosas <farosas@suse.de>
> Closes: https://gitlab.com/qemu-project/qemu/-/issues/2277
> Fixes: 2b3912f135 ("block: Mark bdrv_first_blk() and bdrv_is_root_node() GRAPH_RDLOCK")
> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>

Commit 2b3912f135 is in 8.2 (v8.1.0-1575-g2b3912f135).  Is this fix supposed to go
to stable-8.2 series?  The prob here is that in 8.2, there's no bql_lock/unlock.
I guess it should use qemu_mutex_lock_iothread() instead, for before
195801d700c008 "system/cpus: rename qemu_mutex_lock_iothread() to bql_lock()".

Thanks,

/mjt

> diff --git a/migration/colo.c b/migration/colo.c
> index 84632a603e..5600a43d78 100644
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -835,6 +835,16 @@ static void *colo_process_incoming_thread(void *opaque)
>           return NULL;
>       }
>   
> +    /* Make sure all file formats throw away their mutable metadata */
> +    bql_lock();
> +    bdrv_activate_all(&local_err);
> +    if (local_err) {
> +        bql_unlock();
> +        error_report_err(local_err);
> +        return NULL;
> +    }
> +    bql_unlock();
> +
>       failover_init_state();
>   
>       mis->to_src_file = qemu_file_get_return_path(mis->from_src_file);
> @@ -922,7 +932,6 @@ out:
>   int coroutine_fn colo_incoming_co(void)
>   {
>       MigrationIncomingState *mis = migration_incoming_get_current();
> -    Error *local_err = NULL;
>       QemuThread th;
>   
>       assert(bql_locked());
> @@ -931,13 +940,6 @@ int coroutine_fn colo_incoming_co(void)
>           return 0;
>       }
>   
> -    /* Make sure all file formats throw away their mutable metadata */
> -    bdrv_activate_all(&local_err);
> -    if (local_err) {
> -        error_report_err(local_err);
> -        return -EINVAL;
> -    }
> -
>       qemu_thread_create(&th, "COLO incoming", colo_process_incoming_thread,
>                          mis, QEMU_THREAD_JOINABLE);
>   

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Re: [PATCH v2] migration/colo: Fix bdrv_graph_rdlock_main_loop: Assertion `!qemu_in_coroutine()' failed.

[Peter Xu]

On Sun, Apr 28, 2024 at 03:39:09PM +0300, Michael Tokarev wrote:
> 17.04.2024 05:56, Li Zhijian via wrote:
> > bdrv_activate_all() should not be called from the coroutine context, move
> > it to the QEMU thread colo_process_incoming_thread() with the bql_lock
> > protected.
> > 
> > The backtrace is as follows:
> >   #4  0x0000561af7948362 in bdrv_graph_rdlock_main_loop () at ../block/graph-lock.c:260
> >   #5  0x0000561af7907a68 in graph_lockable_auto_lock_mainloop (x=0x7fd29810be7b) at /patch/to/qemu/include/block/graph-lock.h:259
> >   #6  0x0000561af79167d1 in bdrv_activate_all (errp=0x7fd29810bed0) at ../block.c:6906
> >   #7  0x0000561af762b4af in colo_incoming_co () at ../migration/colo.c:935
> >   #8  0x0000561af7607e57 in process_incoming_migration_co (opaque=0x0) at ../migration/migration.c:793
> >   #9  0x0000561af7adbeeb in coroutine_trampoline (i0=-106876144, i1=22042) at ../util/coroutine-ucontext.c:175
> >   #10 0x00007fd2a5cf21c0 in  () at /lib64/libc.so.6
> > 
> > CC: Fabiano Rosas <farosas@suse.de>
> > Closes: https://gitlab.com/qemu-project/qemu/-/issues/2277
> > Fixes: 2b3912f135 ("block: Mark bdrv_first_blk() and bdrv_is_root_node() GRAPH_RDLOCK")
> > Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
> 
> Commit 2b3912f135 is in 8.2 (v8.1.0-1575-g2b3912f135).  Is this fix supposed to go
> to stable-8.2 series?

Yes we probably should.  I've copied qemu-stable when queuing this patch
for that:

https://lore.kernel.org/r/20240423223813.3237060-27-peterx@redhat.com

> The prob here is that in 8.2, there's no bql_lock/unlock.
> I guess it should use qemu_mutex_lock_iothread() instead, for before
> 195801d700c008 "system/cpus: rename qemu_mutex_lock_iothread() to bql_lock()".

Right, some further care needs to be taken on this one indeed.

> 17.04.2024 05:56, Li Zhijian via wrote:
> > --- a/migration/colo.c
> > +++ b/migration/colo.c
> > @@ -835,6 +835,16 @@ static void *colo_process_incoming_thread(void *opaque)
> >           return NULL;
> >       }
> > +    /* Make sure all file formats throw away their mutable metadata */
> > +    bql_lock();
> > +    bdrv_activate_all(&local_err);
> > +    if (local_err) {
> > +        bql_unlock();
> > +        error_report_err(local_err);
> > +        return NULL;
> > +    }
> > +    bql_unlock();
> 
> FWIW, this can be simplified as follows:
> 
>    bql_lock();
>    bdrv_activate_all(&local_err);
>    bql_unlock();
>    if (local_err) {
>         error_report_err(local_err);
>         return NULL;
>    }
> 
> (I know it is already too late)

Agree. :)

Thanks,

-- 
Peter Xu

Re: [PATCH v2] migration/colo: Fix bdrv_graph_rdlock_main_loop: Assertion `!qemu_in_coroutine()' failed.

[Michael Tokarev]

17.04.2024 05:56, Li Zhijian via wrote:
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -835,6 +835,16 @@ static void *colo_process_incoming_thread(void *opaque)
>           return NULL;
>       }
>   
> +    /* Make sure all file formats throw away their mutable metadata */
> +    bql_lock();
> +    bdrv_activate_all(&local_err);
> +    if (local_err) {
> +        bql_unlock();
> +        error_report_err(local_err);
> +        return NULL;
> +    }
> +    bql_unlock();
FWIW, this can be simplified as follows:

    bql_lock();
    bdrv_activate_all(&local_err);
    bql_unlock();
    if (local_err) {
         error_report_err(local_err);
         return NULL;
    }

(I know it is already too late)

/mjt

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