From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Copy and paste the clear_bit_unlock() implementation, and test the temp
variable to see if it has bit 7 set. Saves two instructions: a load
and a compare:
860: 01 31 20 44 andnot t0,0x1,t0
864: 00 00 30 b8 stl_c t0,0(a0)
868: 67 1b 20 e4 beq t0,7608 <generic_file_write_iter+0x218>
- 86c: 00 00 30 a0 ldl t0,0(a0)
- 870: 01 10 30 44 and t0,0x80,t0
- 874: a1 03 e1 43 cmpult zero,t0,t0
- 878: 01 00 20 f4 bne t0,880 <unlock_page+0x40>
- 87c: 01 80 fa 6b ret
+ 86c: 01 10 30 44 and t0,0x80,t0
+ 870: 03 00 20 f4 bne t0,880 <unlock_page+0x40>
+ 874: 01 80 fa 6b ret
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Richard Henderson <rth@xxxxxxxxxxx>
Cc: Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>
Cc: Matt Turner <mattst88@xxxxxxxxx>
Cc: linux-alpha@xxxxxxxxxxxxxxx
---
arch/alpha/include/asm/bitops.h | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/arch/alpha/include/asm/bitops.h b/arch/alpha/include/asm/bitops.h
index 5adca78830b5..f9af2401bd23 100644
--- a/arch/alpha/include/asm/bitops.h
+++ b/arch/alpha/include/asm/bitops.h
@@ -79,6 +79,29 @@ clear_bit_unlock(unsigned long nr, volatile void * addr)
clear_bit(nr, addr);
}
+static inline bool clear_bit_unlock_is_negative_byte(unsigned int nr,
+ volatile unsigned long *p)
+{
+ unsigned long temp;
+ int *m = ((int *)p) + (nr >> 5);
+
+ smp_mb();
+ __asm__ __volatile__(
+ "1: ldl_l %0,%3\n"
+ " bic %0,%2,%0\n"
+ " stl_c %0,%1\n"
+ " beq %0,2f\n"
+ ".subsection 2\n"
+ "2: br 1b\n"
+ ".previous"
+ :"=&r" (temp), "=m" (*m)
+ :"Ir" (1UL << (nr & 31)), "m" (*m));
+
+ return temp & 128;
+}
+#define clear_bit_unlock_is_negative_byte \
+ clear_bit_unlock_is_negative_byte
+
/*
* WARNING: non atomic version.
*/
--
2.25.1
