On Tue, Mar 31, 2020 at 01:08:00PM +0200, Lars-Peter Clausen wrote: > On 3/31/20 12:58 PM, Sa, Nuno wrote: > > Hi Rohit, > > > > > From: linux-iio-owner@xxxxxxxxxxxxxxx <linux-iio-owner@xxxxxxxxxxxxxxx> On > > > Behalf Of Ardelean, Alexandru > > > Sent: Montag, 30. März 2020 11:20 > > > To: jic23@xxxxxxxxxx; rohitsarkar5398@xxxxxxxxx > > > Cc: stefan.popa@xxxxxxxxxx; zhongjiang@xxxxxxxxxx; linux- > > > iio@xxxxxxxxxxxxxxx; Bogdan, Dragos <Dragos.Bogdan@xxxxxxxxxx>; > > > pmeerw@xxxxxxxxxx; knaack.h@xxxxxx; Hennerich, Michael > > > <Michael.Hennerich@xxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; > > > lars@xxxxxxxxxx > > > Subject: Re: [PATCH 0/2] use DEFINE_DEBUGFS_ATTRIBUTE instead of > > > DEFINE_SIMPLE_ATTRIBUTE > > > > > > On Sun, 2020-03-29 at 10:38 +0100, Jonathan Cameron wrote: > > > > On Sat, 28 Mar 2020 12:04:53 +0530 > > > > Rohit Sarkar <rohitsarkar5398@xxxxxxxxx> wrote: > > > > > > > > > The debugfs_create_file_unsafe method does not protect the fops given to > > > > > it from file removal. It must be used with DEFINE_DEBUGFS_ATTRIBUTE > > > > > which makes the fops aware of the file lifetime. > > > > > > > > > > Further using DEFINE_DEBUGFS_ATTRIBUTE along with > > > > > debugfs_create_file_unsafe significantly reduces the overhead introduced > > > by > > > > > debugfs_create_file which creates a lifetime managing proxy around each > > > > > fops handed in. Refer [1] for more on this. > > > > > > > > > > Fixes the following warnings reported by coccinelle: > > > > > drivers/iio/imu//adis16460.c:126:0-23: WARNING: > > > adis16460_flash_count_fops > > > > > should be defined with DEFINE_DEBUGFS_ATTRIBUTE > > > > > drivers/iio/imu//adis16460.c:108:0-23: WARNING: > > > adis16460_product_id_fops > > > > > should be defined with DEFINE_DEBUGFS_ATTRIBUTE > > > > > drivers/iio/imu//adis16460.c:90:0-23: WARNING: > > > adis16460_serial_number_fops > > > > > should be defined with DEFINE_DEBUGFS_ATTRIBUTE > > > > > drivers/iio/imu//adis16400.c:278:0-23: WARNING: > > > adis16400_flash_count_fops > > > > > should be defined with DEFINE_DEBUGFS_ATTRIBUTE > > > > > drivers/iio/imu//adis16400.c:261:0-23: WARNING: > > > adis16400_product_id_fops > > > > > should be defined with DEFINE_DEBUGFS_ATTRIBUTE > > > > > > > > > > [1]: https://lists.gt.net/linux/kernel/2369498 > > > > > > > > > > Rohit Sarkar (2): > > > > > iio: imu: adis16400: use DEFINE_DEBUGFS_ATTRIBUTE instead of > > > > > DEFINE_SIMPLE_ATTRIBUTE > > > > > iio: imu: adis16460: use DEFINE_DEBUGFS_ATTRIBUTE instead of > > > > > DEFINE_SIMPLE_ATTRIBUTE > > > > > > > > > > drivers/iio/imu/adis16400.c | 4 ++-- > > > > > drivers/iio/imu/adis16460.c | 6 +++--- > > > > > 2 files changed, 5 insertions(+), 5 deletions(-) > > > > > > > > > Hi Rohit, > > > > > > > > You've opened a can of worms with this one. There as a previous series > > > > posted doing exactly this change back in 2019 by Zhong Jiang (cc'd) > > > > > > > > At the time I did a bit of looking into why this had been universally taken > > > > up cross tree and turned out there are some potential issues. > > > > > > > > Alexandru added it to the list of things to test, but I guess it got > > > > buried under other work and is still outstanding. > > > > > > > yep > > > my bad; > > > will try to make room these days for that old one > > > > > > > > I don't have the exact parts that this patch is touching but I have other parts where this patch > > applies and should be same. So, the idea to test this is to read the files in debugfs? Maybe also > > some unbind + binding? > > > > I will try to test this still today... > > The stress test is to open the debugfs file, then unbind the device and then > read from the still open debugfs file. Yes, also just to be sure, we need to test DEFINE_DEBUGFS_ATTRIBUTE along with debugfs_create_file_unsafe. I will send out another patch that changes debugfs_create_file to debugfs_create_file_unsafe and then that can be tested. > - Lars Thanks, Rohit
