From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Kacur Subject: Re: [PATCH] input: remove BKL from uinput open function Date: Mon, 1 Feb 2010 22:04:37 +0100 Message-ID: <520f0cf11002011304w64fac454s8192f271bc27fad6@mail.gmail.com> References: <1264800197-29523-1-git-send-email-cascardo@holoscopio.com> <201001302257.09354.arnd@arndb.de> <520f0cf11001301507k20e3cf8dqa73026e12f3a1767@mail.gmail.com> <201001310520.55813.arnd@arndb.de> <20100131052942.GA12320@core.coreip.homeip.net> <520f0cf11002011222h134dbf06rf1db612da9a9728@mail.gmail.com> <520f0cf11002011227s74e57673j3922941f7ee87989@mail.gmail.com> <20100201204632.GK1414@holoscopio.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-ew0-f228.google.com ([209.85.219.228]:63530 "EHLO mail-ew0-f228.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751409Ab0BAVEi convert rfc822-to-8bit (ORCPT ); Mon, 1 Feb 2010 16:04:38 -0500 In-Reply-To: <20100201204632.GK1414@holoscopio.com> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Thadeu Lima de Souza Cascardo Cc: Dmitry Torokhov , Arnd Bergmann , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org On Mon, Feb 1, 2010 at 9:46 PM, Thadeu Lima de Souza Cascardo wrote: > On Mon, Feb 01, 2010 at 09:27:22PM +0100, John Kacur wrote: >> On Mon, Feb 1, 2010 at 9:22 PM, John Kacur wrote= : >> > On Sun, Jan 31, 2010 at 6:29 AM, Dmitry Torokhov >> > wrote: >> >> On Sun, Jan 31, 2010 at 05:20:55AM +0100, Arnd Bergmann wrote: >> >>> On Sunday 31 January 2010, John Kacur wrote: >> >>> > > Sorry, I should have been clearer, but not implementing llse= ek >> >>> > > is the problem I was referring to: When a driver has no expl= icit >> >>> > > .llseek operation in its file operations and does not call >> >>> > > nonseekable_open from its open operation, the VFS layer will >> >>> > > implicitly use default_llseek, which takes the BKL. We're >> >>> > > in the process of changing drivers not to do this, one by on= e >> >>> > > so we can kill the BKL in the end. >> >>> > > >> >>> > >> >>> > I know we've discussed this before, but why wouldn't the follo= wing >> >>> > make more sense? >> >>> > =A0.llseek =A0 =A0 =A0 =A0 =3D no_llseek, >> >>> >> >>> That's one of the possible solutions. Assigning it to generic_fi= le_llseek >> >>> also gets rid of the BKL but keeps the current behaviour (callin= g seek >> >>> returns success without having an effect, no_llseek returns -ESP= IPE), >> >>> while calling nonseekable_open has the other side-effect of maki= ng >> >>> pread/pwrite fail with -ESPIPE, which is more consistent than >> >>> only failing seek. >> >>> >> >> >> >> OK, so how about the patch below (on top of Thadeu's patch)? >> >> >> >> -- >> >> Dmitry >> >> >> >> Input: uinput - use nonseekable_open >> >> >> >> Seeking does not make sense for uinput so let's use nonseekable_o= pen >> >> to mark the device non-seekable. >> >> >> >> Signed-off-by: Dmitry Torokhov >> >> --- >> >> >> >> =A0drivers/input/misc/uinput.c | =A0 =A07 +++++++ >> >> =A01 files changed, 7 insertions(+), 0 deletions(-) >> >> >> >> >> >> diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uin= put.c >> >> index 18206e1..7089151 100644 >> >> --- a/drivers/input/misc/uinput.c >> >> +++ b/drivers/input/misc/uinput.c >> >> @@ -278,6 +278,7 @@ static int uinput_create_device(struct uinput= _device *udev) >> >> =A0static int uinput_open(struct inode *inode, struct file *file) >> >> =A0{ >> >> =A0 =A0 =A0 =A0struct uinput_device *newdev; >> >> + =A0 =A0 =A0 int error; >> >> >> >> =A0 =A0 =A0 =A0newdev =3D kzalloc(sizeof(struct uinput_device), G= =46P_KERNEL); >> >> =A0 =A0 =A0 =A0if (!newdev) >> >> @@ -291,6 +292,12 @@ static int uinput_open(struct inode *inode, = struct file *file) >> >> >> >> =A0 =A0 =A0 =A0file->private_data =3D newdev; >> >> >> >> + =A0 =A0 =A0 error =3D nonseekable_open(inode, file); >> >> + =A0 =A0 =A0 if (error) { >> >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 kfree(newdev); >> >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 return error; >> >> + =A0 =A0 =A0 } >> >> + >> >> =A0 =A0 =A0 =A0return 0; >> >> =A0} >> >> >> >> >> > >> > Hmnn, if you look at nonseekable_open() it will always return 0. I >> > think you can just do the following. >> > >> > diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinp= ut.c >> > index 18206e1..697c0a6 100644 >> > --- a/drivers/input/misc/uinput.c >> > +++ b/drivers/input/misc/uinput.c >> > @@ -291,7 +291,7 @@ static int uinput_open(struct inode *inode, st= ruct file *fil >> > >> > =A0 =A0 =A0 =A0file->private_data =3D newdev; >> > >> > - =A0 =A0 =A0 return 0; >> > + =A0 =A0 =A0 return nonseekable_open(inode, file); >> > =A0} >> > >> > Signed-off-by: John Kacur >> > >> >> Btw, Thadeu Lima de Souza Cascardo should just combine that all into >> one patch, no point really in making two patches out of that. > > That's fine to me. But since Dmitry has already applied it, I see no > problem at all that this is two commits. Or would there be any proble= m > removing the lock in open and not doing nonseekable_open? > > As far as I get, nonseekable_open only resets the flags that will mak= e > it do the right thing for lseek, pread and pwrite. This will get rid = of > the BKL for these calls, but this is independent of getting rid of it > for the open call. > > I don't disagree that doing both at the same time is OK. But I don't > agree that doing them separately is not OK. This way, you may get the > credits for what you (and not I) have done. =A0:-) > > But either way is fine for me. > > Regards, > Cascardo. > Ok, I didn't know that he already applied it. No need to make a big deal about it, two commits are fine. If he hadn't already applied it then it could logically go together as one commit. John -- To unsubscribe from this list: send the line "unsubscribe linux-input" = in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html