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 <faro...@suse.de>
>
> Cc: qemu-sta...@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 <lizhij...@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();
>
