On 01/12/2023 10:57, Friedrich Weber wrote: > On 17/11/2023 14:09, Wolfgang Bumiller wrote: > [...] >>> return PVE::LXC::Config->lock_config($vmid, $lockcmd); >> >> ^ Here we lock first, then fork the worker, then do `vm_stop` with the >> config lock inherited. >> >> This means that creating multiple shutdown tasks before using one with >> override=true could cause the override task to cancel the *first* ongoing >> shutdown task, then move on to the `lock_config` call - in the meantime >> a second shutdown task acquires this very lock and performs another >> long-running shutdown, causing the `override` parameter to be >> ineffective. > > Just to make sure I understand correctly, the scenario is (please > correct me if I'm wrong): > > * shutdown task #1 has the lock and starts long-running shutdown > * stop API handler with override kills shutdown task #1, but does not > acquire the lock yet > * shutdown task #2 starts, acquires the lock and starts long-running > shutdown > * stop task waits for the lock => override flag was ineffective
Discussed this with Wolfgang off-list, posting here for completeness. I suppose the scenario I sketched is technically possible, but unlikely to occur in practice (the stop API handler will usually acquire the lock before shutdown task #2 can). Wolfgang actually sketched a slightly different scenario, which is reproducible with containers pretty easily: * shutdown task #1 has the lock and starts long-running shutdown * API handler for shutdown task #2 waits for the lock (there is no task yet) * API handler for stop task #3 (with overrule-shutdown) kills shutdown task #1, but does not acquire the lock yet * API handler for shutdown task #2 acquires the lock and runs another long-running shutdown * API handler for stop task #3 waits for the lock => overrule-shutdown flag was ineffective As pointed out by Wolfgang this happens because container shutdown currently uses lock-then-fork. VM shutdown, on the other hand, uses fork-then-lock, so the above can't happen (the stop task with overrule-shutdown kills both shutdown tasks). In the next version I'll send a separate patch that switches the ordering as suggested by Wolfgang. _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
