On Mon, 26 Jul 2021 20:03:14 +0800 hui.liu <hui.liu@xxxxxxxxxxxx> wrote: > On Sat, 2021-07-24 at 18:30 +0100, Jonathan Cameron wrote: > > On Fri, 23 Jul 2021 20:21:15 +0800 > > hui.liu <hui.liu@xxxxxxxxxxxx> wrote: > > > > > On Sat, 2021-07-17 at 17:44 +0100, Jonathan Cameron wrote: > > > > On Thu, 15 Jul 2021 17:35:23 +0800 > > > > Hui Liu <hui.liu@xxxxxxxxxxxx> wrote: > > > > > > > > > Add mutex_destroy when probe fail and remove device. > > > > > > > > > > Signed-off-by: Hui Liu <hui.liu@xxxxxxxxxxxx> > > > > Hi Hui Liu, > > > > > > > > We very very rarely bother to call mutex_destroy(). The reason is > > > > that it is only a non noop in when mutex debugging is enabled and > > > > that is only useful if there is a plausible route in which it could > > > > be used after the mutex_destroy. Given these are both at the ends > > > > of removal paths, I don't think this is useful. That's why you will > > > > rarely find mutex_destroy() being called. > > > > > > > > Thanks, > > > > > > > > Jonathan > > > > > > Hi Jonathon, > > > > > > I think this patch could assurance the integrity of code. > > > mutex_init will be called when driver probe. If driver probe fail or > > > device removed, mutex_destroy could set lock->magic to NULL. > > > > I'm not seeing the use case here given the location doesn't leave > > a huge amount of code that could have such a bug. There might have been > > something if we had any route to increment the reference count of the > > structure this mutex is ultimately embedded in and so have it outlast > > the remove function or error path. In this driver it looks like there is > > no such path. Hence you are protecting against a automated > > cleanup of core code (nothing in the driver itself) which is obviously > > not going to try taking a driver specific mutex. > > > > A few side notes: > > > > You are calling it wrong place in remove. The ordering in remove > > should be the opposite of that in probe so the mutex_destroy should either > > be a few lines earlier, or you should have a comment there to say why you > > are doing it where you have chosen to do so. > > > > The style of this probe is to do error handling in a block at the end. > > So this handling should be there, not in the if statement. > > > > Jonathan > > > > > Hi Jonathon, > > Base on your helpful opinion, We will to do two changes in patch v2. > 1. In probe: move mutex_destroy from the if statement to error handling > path(err_power_off). > 2. In remove: calling mutex_destroy right after iio_device_unregister. > > Do we need some more change? Thanks. Ah. Sorry I missed this in the flood of emails during the week. Anyhow, I've replied to the v1 posting. Jonathan > > > > > > > > Thanks. > > > Hui > > > > > > > > > > > > --- > > > > > drivers/iio/adc/mt6577_auxadc.c | 2 ++ > > > > > 1 file changed, 2 insertions(+) > > > > > > > > > > diff --git a/drivers/iio/adc/mt6577_auxadc.c b/drivers/iio/adc/mt6577_auxadc.c > > > > > index 79c1dd68b909..d57243037ad6 100644 > > > > > --- a/drivers/iio/adc/mt6577_auxadc.c > > > > > +++ b/drivers/iio/adc/mt6577_auxadc.c > > > > > @@ -289,6 +289,7 @@ static int mt6577_auxadc_probe(struct platform_device *pdev) > > > > > ret = iio_device_register(indio_dev); > > > > > if (ret < 0) { > > > > > dev_err(&pdev->dev, "failed to register iio device\n"); > > > > > + mutex_destroy(&adc_dev->lock); > > > > > goto err_power_off; > > > > > } > > > > > > > > > > @@ -313,6 +314,7 @@ static int mt6577_auxadc_remove(struct platform_device *pdev) > > > > > 0, MT6577_AUXADC_PDN_EN); > > > > > > > > > > clk_disable_unprepare(adc_dev->adc_clk); > > > > > + mutex_destroy(&adc_dev->lock); > > > > > > > > > > return 0; > > > > > } > > > > > > > > > >