Hello everybody, I am using stock ubuntu natty with lvmlib 2.02.66. In my application I would like to have several threads, each operating on a different VG. When I tried to share the same lvm_t handle between the threads, very soon I got segmentation faults in dm_hash operations. Looking at the code, I indeed saw that the contents of lvm_t are used without synchronization. So I tried to use a lvm_t handle per thread. Quite soon I ran into the following scenario: - when a thread calls lvm_init(), this function calls init_locking(). By default LVM uses file-based locking. So init_file_locking() is called. This function resets the global _lock_list structure. So any previous locks are forgotten. - as a result, when another thread wants to unlock a previously-locked VG, it scans the _lock_list, does not find the lock there and returns an error (although lvm_vg_close() hides that error by always returning 0). - however, the dm_hash that contains the locked VG name is not updated and still contains that name. So the user thinks that the VG got unlocked, but dm_hash thinks otherwise. Since now there is no way to unlock this VG (it’s file-lock was forgotten), the dm_hash entry cannot be removed. This might prevent locking other VGs (because of VG lock order enforcement), but from the user’s point of view, he should be able to lock new VGs. Can somebody of the lvmlib developers please comment on those issues? Basically, as I see it, my application should use a single lvm_t handle and do not share access to it, or synchronize all access between lvm_vg_create/lvm_vg_open and lvm_vg_close. Are there any plans or intentions to provide some support for threading with lvmlib? Thanks, Alex. _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
