regulator: dummy: force synchronous probing

In the Linux kernel, the following vulnerability has been resolved: regulator: dummy: force synchronous probing Sometimes I get a NULL pointer dereference at boot time in kobject_get() with the following call stack: anatop_regulator_probe() devm_regulator_register() regulator_register() regulator_resolve_supply() kobject_get() By placing some extra BUG_ON() statements I could verify that this is raised because probing of the 'dummy' regulator driver is not completed ('dummy_regulator_rdev' is still NULL). In the JTAG debugger I can see that dummy_regulator_probe() and anatop_regulator_probe() can be run by different kernel threads (kworker/u4:*). I haven't further investigated whether this can be changed or if there are other possibilities to force synchronization between these two probe routines. On the other hand I don't expect much boot time penalty by probing the 'dummy' regulator synchronously.