On Tue 12 Sep 2017 01:17:38 PM CEST, WangJie (Captain) wrote: > Hi, Kevin. > > I found a bug about qemu-kvm(version 2.7.0-rc0 adn 2.8.1). but qemu 2.6.0 and > current master is OK. > So I git-bisect the master branch，and I found the patch you commited (block: > Decouple throttling from BlockDriverState) lead the bug into qemu. > > The patch which lead the bug into qemu: > (https://github.com/qemu/qemu/commit/7ca7f0f6db1fedd28d490795d778cf23979a2aa7#diff-ea36ba0f79150cc299732696a069caba) > > Because the current master is OK. So I think you had fixed it , can you tell > me which patch fixed the bug? Thank you :> > > > the bug is that: qemu will crash when loop to attach and detach a disk which > configured qos to a VM for a while. > > > *Segmentation fault info(qemu 2.7.0-rc0):* > Using host libthread_db library "/lib64/libthread_db.so.1". > Core was generated by `/usr/bin/qemu-kvm -name > guest=wangjie-i-clone203_rhel_7.3_64_guestosdev,debug-t'. > Program terminated with signal 11, Segmentation fault. > #0 0x00007fe960413e3c in throttle_group_next_blk (blk=0x11) at > block/throttle-groups.c:160
That's clearly an invalid pointer, so the code is iterating over a BlockBackend that has either been freed or is not on the throttle_groups list anymore. Commit 6bf77e1c2dc24da1bade16e8a9a637f3b127314d fixed a problem in which the code was not iterating the list correctly, although I don't think that would have caused any crash. Did you try using git-bisect to find the commit that fixed the bug? Berto
