On 06/15/2016 01:45 PM, Peter Zijlstra wrote:
On Tue, Jun 14, 2016 at 06:48:08PM -0400, Waiman Long wrote:
+++ b/arch/alpha/include/asm/rwsem.h
@@ -17,9 +17,9 @@
#define RWSEM_UNLOCKED_VALUE 0x0000000000000000L
#define RWSEM_ACTIVE_BIAS 0x0000000000000001L
#define RWSEM_ACTIVE_MASK 0x00000000ffffffffL
-#define RWSEM_WAITING_BIAS (-0x0000000100000000L)
+#define RWSEM_WAITING_BIAS 0xc000000000000000L
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
-#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
+#define RWSEM_ACTIVE_WRITE_BIAS (-RWSEM_ACTIVE_MASK)
+++ b/arch/ia64/include/asm/rwsem.h
@@ -30,9 +30,9 @@
#define RWSEM_UNLOCKED_VALUE __IA64_UL_CONST(0x0000000000000000)
#define RWSEM_ACTIVE_BIAS (1L)
#define RWSEM_ACTIVE_MASK (0xffffffffL)
-#define RWSEM_WAITING_BIAS (-0x100000000L)
+#define RWSEM_WAITING_BIAS (-(1L<< 62))
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
-#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
+#define RWSEM_ACTIVE_WRITE_BIAS (-RWSEM_ACTIVE_MASK)
+++ b/arch/s390/include/asm/rwsem.h
@@ -42,9 +42,9 @@
#define RWSEM_UNLOCKED_VALUE 0x0000000000000000L
#define RWSEM_ACTIVE_BIAS 0x0000000000000001L
#define RWSEM_ACTIVE_MASK 0x00000000ffffffffL
-#define RWSEM_WAITING_BIAS (-0x0000000100000000L)
+#define RWSEM_WAITING_BIAS 0xc000000000000000L
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
-#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
+#define RWSEM_ACTIVE_WRITE_BIAS (-RWSEM_ACTIVE_MASK)
+++ b/arch/x86/include/asm/rwsem.h
@@ -41,21 +41,23 @@
/*
* The bias values and the counter type limits the number of
- * potential readers/writers to 32767 for 32 bits and 2147483647
- * for 64 bits.
+ * potential writers to 16383 for 32 bits and 1073741823 for 64 bits.
+ * The combined readers and writers can go up to 65534 for 32-bits and
+ * 4294967294 for 64-bits.
*/
#ifdef CONFIG_X86_64
# define RWSEM_ACTIVE_MASK 0xffffffffL
+# define RWSEM_WAITING_BIAS (-(1L<< 62))
#else
# define RWSEM_ACTIVE_MASK 0x0000ffffL
+# define RWSEM_WAITING_BIAS (-(1L<< 30))
#endif
#define RWSEM_UNLOCKED_VALUE 0x00000000L
#define RWSEM_ACTIVE_BIAS 0x00000001L
-#define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1)
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
-#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
+#define RWSEM_ACTIVE_WRITE_BIAS (-RWSEM_ACTIVE_MASK)
+++ b/include/asm-generic/rwsem.h
@@ -18,15 +18,16 @@
*/
#ifdef CONFIG_64BIT
# define RWSEM_ACTIVE_MASK 0xffffffffL
+# define RWSEM_WAITING_BIAS (-(1L<< 62))
#else
# define RWSEM_ACTIVE_MASK 0x0000ffffL
+# define RWSEM_WAITING_BIAS (-(1L<< 30))
#endif
#define RWSEM_UNLOCKED_VALUE 0x00000000L
#define RWSEM_ACTIVE_BIAS 0x00000001L
-#define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1)
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
-#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
+#define RWSEM_ACTIVE_WRITE_BIAS (-RWSEM_ACTIVE_MASK)
Can't we collapse all that? They all seem very similar.
Yes, they are actually the same. I think we could extract the macro
definitions into asm-generic/rwsem-macros.h, for instance, and make the
architecture specific header file include the new generic header.
Cheers,
Longman
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