We ran into the limit with the maximum number of waiters at one of our sites.
This patch increases the number of possible waiters from 2^15 to 2^31 by using
a long for the counter in struct rw_semaphore.
Signed-off-by: Christoph Lameter <[EMAIL PROTECTED]>
Index: linux-2.6.13-rc6/include/asm-ia64/rwsem.h
===================================================================
--- linux-2.6.13-rc6.orig/include/asm-ia64/rwsem.h 2005-08-07
11:18:56.000000000 -0700
+++ linux-2.6.13-rc6/include/asm-ia64/rwsem.h 2005-08-22 12:17:13.000000000
-0700
@@ -3,6 +3,7 @@
*
* Copyright (C) 2003 Ken Chen <[EMAIL PROTECTED]>
* Copyright (C) 2003 Asit Mallick <[EMAIL PROTECTED]>
+ * Copyright (C) 2005 Christoph Lameter <[EMAIL PROTECTED]>
*
* Based on asm-i386/rwsem.h and other architecture implementation.
*
@@ -11,9 +12,9 @@
*
* The lock count is initialized to 0 (no active and no waiting lockers).
*
- * When a writer subtracts WRITE_BIAS, it'll get 0xffff0001 for the case
- * of an uncontended lock. Readers increment by 1 and see a positive value
- * when uncontended, negative if there are writers (and maybe) readers
+ * When a writer subtracts WRITE_BIAS, it'll get 0xffffffff00000001 for
+ * the case of an uncontended lock. Readers increment by 1 and see a positive
+ * value when uncontended, negative if there are writers (and maybe) readers
* waiting (in which case it goes to sleep).
*/
@@ -29,7 +30,7 @@
* the semaphore definition
*/
struct rw_semaphore {
- signed int count;
+ signed long count;
spinlock_t wait_lock;
struct list_head wait_list;
#if RWSEM_DEBUG
@@ -37,10 +38,10 @@ struct rw_semaphore {
#endif
};
-#define RWSEM_UNLOCKED_VALUE 0x00000000
-#define RWSEM_ACTIVE_BIAS 0x00000001
-#define RWSEM_ACTIVE_MASK 0x0000ffff
-#define RWSEM_WAITING_BIAS (-0x00010000)
+#define RWSEM_UNLOCKED_VALUE __IA64_UL_CONST(0x0000000000000000)
+#define RWSEM_ACTIVE_BIAS __IA64_UL_CONST(0x0000000000000001)
+#define RWSEM_ACTIVE_MASK __IA64_UL_CONST(0x00000000ffffffff)
+#define RWSEM_WAITING_BIAS -__IA64_UL_CONST(0x0000000100000000)
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS +
RWSEM_ACTIVE_BIAS)
@@ -83,7 +84,7 @@ init_rwsem (struct rw_semaphore *sem)
static inline void
__down_read (struct rw_semaphore *sem)
{
- int result = ia64_fetchadd4_acq((unsigned int *)&sem->count, 1);
+ long result = ia64_fetchadd8_acq((unsigned long *)&sem->count, 1);
if (result < 0)
rwsem_down_read_failed(sem);
@@ -95,7 +96,7 @@ __down_read (struct rw_semaphore *sem)
static inline void
__down_write (struct rw_semaphore *sem)
{
- int old, new;
+ long old, new;
do {
old = sem->count;
@@ -112,7 +113,7 @@ __down_write (struct rw_semaphore *sem)
static inline void
__up_read (struct rw_semaphore *sem)
{
- int result = ia64_fetchadd4_rel((unsigned int *)&sem->count, -1);
+ long result = ia64_fetchadd8_rel((unsigned long *)&sem->count, -1);
if (result < 0 && (--result & RWSEM_ACTIVE_MASK) == 0)
rwsem_wake(sem);
@@ -124,7 +125,7 @@ __up_read (struct rw_semaphore *sem)
static inline void
__up_write (struct rw_semaphore *sem)
{
- int old, new;
+ long old, new;
do {
old = sem->count;
@@ -141,7 +142,7 @@ __up_write (struct rw_semaphore *sem)
static inline int
__down_read_trylock (struct rw_semaphore *sem)
{
- int tmp;
+ long tmp;
while ((tmp = sem->count) >= 0) {
if (tmp == cmpxchg_acq(&sem->count, tmp, tmp+1)) {
return 1;
@@ -156,7 +157,7 @@ __down_read_trylock (struct rw_semaphore
static inline int
__down_write_trylock (struct rw_semaphore *sem)
{
- int tmp = cmpxchg_acq(&sem->count, RWSEM_UNLOCKED_VALUE,
+ long tmp = cmpxchg_acq(&sem->count, RWSEM_UNLOCKED_VALUE,
RWSEM_ACTIVE_WRITE_BIAS);
return tmp == RWSEM_UNLOCKED_VALUE;
}
@@ -167,7 +168,7 @@ __down_write_trylock (struct rw_semaphor
static inline void
__downgrade_write (struct rw_semaphore *sem)
{
- int old, new;
+ long old, new;
do {
old = sem->count;
@@ -182,7 +183,7 @@ __downgrade_write (struct rw_semaphore *
* Implement atomic add functionality. These used to be "inline" functions,
but GCC v3.1
* doesn't quite optimize this stuff right and ends up with bad calls to
fetchandadd.
*/
-#define rwsem_atomic_add(delta, sem) atomic_add(delta, (atomic_t
*)(&(sem)->count))
-#define rwsem_atomic_update(delta, sem) atomic_add_return(delta,
(atomic_t *)(&(sem)->count))
+#define rwsem_atomic_add(delta, sem) atomic64_add(delta, (atomic64_t
*)(&(sem)->count))
+#define rwsem_atomic_update(delta, sem) atomic64_add_return(delta,
(atomic64_t *)(&(sem)->count))
#endif /* _ASM_IA64_RWSEM_H */
-
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