On 2019/3/11 20:46, Dan Carpenter wrote: > On Mon, Mar 11, 2019 at 05:51:15PM +0800, Mao Wenan wrote: >> Add the missing uart_unregister_driver() before return >> from sci_probe_single() in the error handling case. >> >> Signed-off-by: Mao Wenan <maowenan@xxxxxxxxxx> >> --- > > Sorry, I didn't really look at the code when I saw the v1 patch. > > There are other error paths, but actually the whole approach is wrong. > Please, read my google plus post about error handling: > > https://plus.google.com/u/0/106378716002406849458/posts/1Ud9JbaYnPr > OK. > But then the other rule I didn't mention in that post which applies > here is that the error handling should "mirror" the allocation code > so if you have: > > if (foo) { > ret = allocate_one(); > if (ret) > return ret; > } > ret = allocate_two(); > if (ret) > goto free_one; > > The error handling should mirror the "if (foo) " condition. Like this: > > free_one: > if (foo) > free_one(); > > Even if you can do extra analysis and find that the "if (foo) " can > be removed, you should leave there, because the mirroring helps human > readers. > > In this case, the code is doing: > > drivers/tty/serial/sh-sci.c > 3259 return -EBUSY; > 3260 > 3261 mutex_lock(&sci_uart_registration_lock); > 3262 if (!sci_uart_driver.state) { > ^^^^^^^^^^^^^^^^^^^^^^ > 3263 ret = uart_register_driver(&sci_uart_driver); > 3264 if (ret) { > 3265 mutex_unlock(&sci_uart_registration_lock); > 3266 return ret; > 3267 } > 3268 } > 3269 mutex_unlock(&sci_uart_registration_lock); > 3270 > > We would have to mirror the "if (!sci_uart_driver.state) {" code. > > But actually, we can't. > > The first driver to hit this code is supposed to load the > sci_uart_driver. We can't know if we are the last driver to stop using > the sci_uart_driver so we can't know if we can free it. This looks like > a very ugly hack to me. It should probably be using ref counters. It seems something should be considered deeply. > > regards, > an carpenter > > . >
