Re: [RFC PATCH-tip v2 5/6] locking/rwsem: Change RWSEM_WAITING_BIAS for better disambiguation
From: Peter Zijlstra <peterz@infradead.org>
Date: 2016-06-15 17:45:20
Also in:
linux-arch, linux-s390, lkml
On Tue, Jun 14, 2016 at 06:48:08PM -0400, Waiman Long wrote:
quoted hunk ↗ jump to hunk
+++ 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)
quoted hunk ↗ jump to hunk
+++ 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)
quoted hunk ↗ jump to hunk
+++ 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)
quoted hunk ↗ jump to hunk
+++ 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)
quoted hunk ↗ jump to hunk
+++ 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.