On Sat, Dec 10, 2016 at 02:38:41PM +0200, Vladimir Zapolskiy wrote: > Hello Greg, > > On 12/10/2016 09:32 AM, Greg Kroah-Hartman wrote: > > On Sat, Dec 10, 2016 at 02:15:19AM +0200, Vladimir Zapolskiy wrote: > >> If CONFIG_DEBUG_TEST_DRIVER_REMOVE option is enabled a number of false > >> positives are reported for ATA controller drivers, because ATA port > >> probes are done asynchronously, and the same problem may also touch > >> other asynchronously probed drivers. > >> > >> To reduce the rate of false reports on boot call async_synchronize_full() > >> before attempting to remove a driver, the same is done in delete_module() > >> syscall for all possible drivers and in __device_release_driver() function > >> for asynchronously probed drivers. > > > > __device_release_driver() already calls this function, why call it > > again? > > > > __device_release_driver() is not called on test removal of drivers, if > CONFIG_DEBUG_TEST_DRIVER_REMOVE option is enabled. > > This opens a possibility to races like one I've discovered: > > https://www.spinics.net/lists/linux-ide/msg53473.html > > Next, async_synchronize_full() from __device_release_driver() is not > called in case of removal of ATA controller drivers, because > driver_allows_async_probing(drv) return value is false.
Hm, how does this not also get hit if you unbind/bind/unbind/bind/etc. from userspace as well? I don't think this is a CONFIG_DEBUG_TEST_DRIVER_REMOVE issue, but just that this option finds the problem corner cases as you are finding out :) thanks, greg k-h