On Fri, Jun 17, 2016 at 03:06:33PM -0400, Waiman Long wrote:
> On 06/15/2016 05:31 AM, 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>
> >---
> >change from v1:
> > A typo fix which is really bad...
> > thanks Will for the carefull review. :)
> >---
> > 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..28fb94a 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_SHIFT 0 /* Writer mode shift */
> >+#else
> >+#define _QR_SHIFT 0 /* Reader count shift */
> >+#define _QW_SHIFT 24 /* Writer mode shift */
> >+#endif
> >+
> >+#define _QW_WAITING (1U<< _QW_SHIFT) /* A writer is waiting */
> >+#define _QW_LOCKED (0xffU<< _QW_SHIFT) /* A writer holds the lock */
> >+#define _QW_WMASK (0xffU<< _QW_SHIFT) /* Writer mask */
> >+#define _QR_BIAS (1U<< _QR_SHIFT)
> >
> > /*
> > * External function declarations
> >diff --git a/kernel/locking/qrwlock.c b/kernel/locking/qrwlock.c
> >index fec0823..57d66cf 100644
> >--- a/kernel/locking/qrwlock.c
> >+++ b/kernel/locking/qrwlock.c
> >@@ -30,18 +30,15 @@ struct __qrwlock {
> > union {
> > atomic_t cnts;
> > struct {
> >-#ifdef __LITTLE_ENDIAN
> > u8 wmode; /* Writer mode */
> > u8 rcnts[3]; /* Reader counts */
> >-#else
> >- u8 rcnts[3]; /* Reader counts */
> >- u8 wmode; /* Writer mode */
> >-#endif
> > };
> > };
> > arch_spinlock_t lock;
> > };
> >
> >+#define _QW_MODEVAL(v) ((v)>> _QW_SHIFT)
>
> I know what you are doing here, but it is a bit hard to understand it just
> by looking at the name of the macro itself. Maybe some other names like
> _QW_MASKVAL() or_QW_BYTEVAL(). You may also want to have a line of comment
> about it. Other than that, I don't see any problem with it.
>
> Acked-by: Waiman Long <Waiman.Long@xxxxxxx>
I agree that the macro is ugly. I think I'd be inclined to drop it
altogether.
That said, the code looks correct to me:
Reviewed-by: Will Deacon <will.deacon@xxxxxxx>
Will
--
To unsubscribe from this list: send the line "unsubscribe linux-arch" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
