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Marc-André reported an issue on QEMU crash when retrying a cancelled migration during early setup phase, see "Link:" for more information, and also easy way to reproduce. This patch is a replacement of the prior fix proposed by not only switching to migration_cleanup(), but also fixing it from CPR side, so that we track hup_source properly to know if src QEMU is waiting or the HUP signal. To put it simple: this chunk of special casing in migration_cancel() should not affect normal migration, but only cpr-transfer migration to cover the small window when the src QEMU is waiting for a HUP signal on cpr channel (so that src QEMU can continue the migration on the main channel). To achieve that, we'll also need to remember to detach the hup_source whenenver invoked: after that point, we should always be able to cleanup the migration. It's not a generic operation to explicitly detach a gsource from its context while in its dispatch() function. But it should be safe, because gsource disptch() will only happen with a boosted refcount for the dispatcher so that the gsource will not be freed until the callback completes. It's also safe to return G_SOURCE_REMOVE after the gsource is detached, as glib will simply ignore the G_SOURCE_REMOVE. One can refer to latest 2.86.5 glib code in g_main_dispatch() for that: https://github.com/GNOME/glib/blob/2.86.5/glib/gmain.c#L3592 When at this, add a bunch of assertions to make sure nothing surprises us. After this patch applied, the 2nd migration will not crash QEMU, instead it'll be in CANCELLING until the socket connection times out (it will take ~2min on my Fedora default kernel). During this process no 2nd migration will be allowed, and after it timed out migration can be restarted. It's because so far we don't have control over socket_connect_outgoing(), or anything yet managed by a task executed in qio_task_run_in_thread(). Speeding up the cancellation to be left for future. I also tested cpr-transfer by only providing cpr channel not the main channel (with -incoming defer), kickoff migration on source, then cancel it on source directly without providing the main channel. It keeps working. I wanted to add an unit test for that but it'll need to refactor current cpr-transfer tests first; let's leave it for later. Link: https://lore.kernel.org/r/20260417184742.293061-1-marcandre.lureau@redhat.com Reported-by: Marc-André Lureau <marcandre.lureau@redhat.com> Tested-by: Fabiano Rosas <farosas@suse.de> Reviewed-by: Fabiano Rosas <farosas@suse.de> Link: https://lore.kernel.org/r/20260421175820.302795-1-peterx@redhat.com Signed-off-by: Peter Xu <peterx@redhat.com>