[libvirt PATCH] nodedev: Don't crash when exiting before init is done

[Michal Privoznik]

On 3/16/21 11:27 PM, Jonathon Jongsma wrote:
> If libvirtd is terminated before the node driver finishes
> initialization, it can crash with a backtrace similar to the following:
> 
>      Stack trace of thread 1922933:
>      #0  0x00007f8515178774 g_hash_table_find (libglib-2.0.so.0)
>      #1  0x00007f851593ea98 virHashSearch (libvirt.so.0)
>      #2  0x00007f8515a1dd83 virNodeDeviceObjListSearch (libvirt.so.0)
>      #3  0x00007f84cceb40a1 udevAddOneDevice (libvirt_driver_nodedev.so)
>      #4  0x00007f84cceb5fae nodeStateInitializeEnumerate (libvirt_driver_nodedev.so)
>      #5  0x00007f85159840cb virThreadHelper (libvirt.so.0)
>      #6  0x00007f8511c7d14a start_thread (libpthread.so.0)
>      #7  0x00007f851442bdb3 __clone (libc.so.6)
> 
>      Stack trace of thread 1922863:
>      #0  0x00007f851442651d syscall (libc.so.6)
>      #1  0x00007f85159842d4 virThreadSelfID (libvirt.so.0)
>      #2  0x00007f851594e240 virLogFormatString (libvirt.so.0)
>      #3  0x00007f851596635d vir_object_finalize (libvirt.so.0)
>      #4  0x00007f8514efe8e9 g_object_unref (libgobject-2.0.so.0)
>      #5  0x00007f85159667f8 virObjectUnref (libvirt.so.0)
>      #6  0x00007f851517755f g_hash_table_remove_all_nodes.part.0 (libglib-2.0.so.0)
>      #7  0x00007f8515177e62 g_hash_table_unref (libglib-2.0.so.0)
>      #8  0x00007f851596637e vir_object_finalize (libvirt.so.0)
>      #9  0x00007f8514efe8e9 g_object_unref (libgobject-2.0.so.0)
>      #10 0x00007f85159667f8 virObjectUnref (libvirt.so.0)
>      #11 0x00007f84cceb2b42 nodeStateCleanup (libvirt_driver_nodedev.so)
>      #12 0x00007f8515b37950 virStateCleanup (libvirt.so.0)
>      #13 0x00005648085348e8 main (libvirtd)
>      #14 0x00007f8514352493 __libc_start_main (libc.so.6)
>      #15 0x00005648085350fe _start (libvirtd)
> 
> This is because the initial population of the device list is done in a
> separate initialization thread. If we attempt to exit libvirtd before
> this init thread has completed, we'll try to free the device list while
> accessing it from the other thread. In order to guarantee that this
> init thread is not accessing the device list when we're cleaning up the
> nodedev driver, make it joinable and wait for it to finish before
> proceding with the cleanup. This is similar to how we handle the udev
> event handler thread.
> 
> The separate initialization thread was added in commit
> 9f0ae0b1.
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=1933590

Since this bug was closed as a duplicate of 1836865, I'm replacing this 
line. Hope you don't mind.

> 
> Signed-off-by: Jonathon Jongsma <jjongsma at redhat.com>
> ---
>   src/node_device/node_device_udev.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)

Reviewed-by: Michal Privoznik <mprivozn at redhat.com>

And pushed.

Michal