Re: [PATCH 2/3] migration/multifd: fix destroyed mutex access in terminating multifd threads

[Juan Quintela]

cenjiahui <address@hidden> wrote:
> From: Jiahui Cen <address@hidden>
>
> One multifd will lock all the other multifds' IOChannel mutex to inform them
> to quit by setting p->quit or shutting down p->c. In this senario, if some
> multifds had already been terminated and 
> multifd_load_cleanup/multifd_save_cleanup
> had destroyed their mutex, it could cause destroyed mutex access when trying
> lock their mutex.
>
> Here is the coredump stack:
>     #0  0x00007f81a2794437 in raise () from /usr/lib64/libc.so.6
>     #1  0x00007f81a2795b28 in abort () from /usr/lib64/libc.so.6
>     #2  0x00007f81a278d1b6 in __assert_fail_base () from /usr/lib64/libc.so.6
>     #3  0x00007f81a278d262 in __assert_fail () from /usr/lib64/libc.so.6
>     #4  0x000055eb1bfadbd3 in qemu_mutex_lock_impl (mutex=0x55eb1e2d1988, 
> file=<optimized out>, line=<optimized out>) at util/qemu-thread-posix.c:64
>     #5  0x000055eb1bb4564a in multifd_send_terminate_threads (err=<optimized 
> out>) at migration/ram.c:1015
>     #6  0x000055eb1bb4bb7f in multifd_send_thread (opaque=0x55eb1e2d19f8) at 
> migration/ram.c:1171
>     #7  0x000055eb1bfad628 in qemu_thread_start (args=0x55eb1e170450) at 
> util/qemu-thread-posix.c:502
>     #8  0x00007f81a2b36df5 in start_thread () from /usr/lib64/libpthread.so.0
>     #9  0x00007f81a286048d in clone () from /usr/lib64/libc.so.6
>
> To fix it up, let's destroy the mutex after all the other multifd threads had
> been terminated.
>
> Signed-off-by: Jiahui Cen <address@hidden>
> Signed-off-by: Ying Fang <address@hidden>

Reviewed-by: Juan Quintela <address@hidden>