Re: [PATCH] locking/qrwlock: Let qrwlock has same layout regardless of the endian

[xinhui]

On 2016å06æ15æ 17:20, Will Deacon wrote:
> On Wed, Jun 15, 2016 at 05:16:17PM +0800, Pan Xinhui wrote:
> > This patch aims to get rid of endianness in queued_write_unlock(). We
> > want to set  __qrwlock->wmode to NULL, however the address is not
> > &lock->cnts in big endian machine. That causes queued_write_unlock()
> > write NULL to the wrong field of __qrwlock.
> >
> > Actually qrwlock can have same layout, IOW we can remove the #if
> > __little_endian in struct __qrwlock. With such modification, we only
> > need define some _QW* and _QR* with corresponding values in different
> > endian systems.
> >
> > Suggested-by: Will Deacon <will.deacon@xxxxxxx>
> > Signed-off-by: Pan Xinhui <xinhui.pan@xxxxxxxxxxxxxxxxxx>
> > ---
> >   include/asm-generic/qrwlock.h | 15 +++++++++++----
> >   kernel/locking/qrwlock.c      | 10 ++++------
> >   2 files changed, 15 insertions(+), 10 deletions(-)
> >
> > diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h
> > index 54a8e65..b135c11 100644
> > --- a/include/asm-generic/qrwlock.h
> > +++ b/include/asm-generic/qrwlock.h
> > @@ -27,11 +27,18 @@
> >   /*
> >    * Writer states & reader shift and bias
> >    */
> > -#define	_QW_WAITING	1		/* A writer is waiting	   */
> > -#define	_QW_LOCKED	0xff		/* A writer holds the lock */
> > -#define	_QW_WMASK	0xff		/* Writer mask		   */
> > +#ifdef	__LITTLE_ENDIAN
> >   #define	_QR_SHIFT	8		/* Reader count shift	   */
> > -#define _QR_BIAS	(1U << _QR_SHIFT)
> > +#define	_QW_SHIFF	0		/* Writer mode shift	*/
>
> Well, there are other typos that could've been worse, but you probably
> want to fix this...
oh... I am really in rush. sorry. will fix it and seed patch v2 soon.

thank you for pointing it out.

> Will