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.
Cc: stable@vger.kernel.org Fixes: 259b93b21a9f ("regulator: Set PROBE_PREFER_ASYNCHRONOUS for drivers that existed in 4.14") Signed-off-by: Christian Eggers ceggers@arri.de --- v2: - no changes
v3: - no changes
drivers/regulator/dummy.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/regulator/dummy.c b/drivers/regulator/dummy.c index 5b9b9e4e762d..9f59889129ab 100644 --- a/drivers/regulator/dummy.c +++ b/drivers/regulator/dummy.c @@ -60,7 +60,7 @@ static struct platform_driver dummy_regulator_driver = { .probe = dummy_regulator_probe, .driver = { .name = "reg-dummy", - .probe_type = PROBE_PREFER_ASYNCHRONOUS, + .probe_type = PROBE_FORCE_SYNCHRONOUS, }, };