Prev: [PATCH 04/10] rwsem: let RWSEM_WAITING_BIAS represent any number of waiting threads
Next: [PATCH 07/10] generic rwsem: implement down_read_unfair
From: Michel Lespinasse on 14 May 2010 08:50
More code can be pushed from rwsem_down_read_failed and
rwsem_down_write_failed into rwsem_down_failed_common.

Following change adding down_read_unfair infrastructure support also
enjoys having flags available in a register rather than having to
fish it out in the struct rwsem_waiter...

Signed-off-by: Michel Lespinasse <walken(a)google.com>
---
lib/rwsem.c | 25 ++++++++++---------------
1 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/lib/rwsem.c b/lib/rwsem.c
index 6e1200e..2dd1a1b 100644
--- a/lib/rwsem.c
+++ b/lib/rwsem.c
@@ -170,8 +170,9 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wake_type)
*/
static struct rw_semaphore __sched *
rwsem_down_failed_common(struct rw_semaphore *sem,
- struct rwsem_waiter *waiter, signed long adjustment)
+ unsigned int flags, signed long adjustment)
{
+ struct rwsem_waiter waiter;
struct task_struct *tsk = current;
signed long count;

@@ -179,12 +180,13 @@ rwsem_down_failed_common(struct rw_semaphore *sem,

/* set up my own style of waitqueue */
spin_lock_irq(&sem->wait_lock);
- waiter->task = tsk;
+ waiter.task = tsk;
+ waiter.flags = flags;
get_task_struct(tsk);

if (list_empty(&sem->wait_list))
adjustment += RWSEM_WAITING_BIAS;
- list_add_tail(&waiter->list, &sem->wait_list);
+ list_add_tail(&waiter.list, &sem->wait_list);

/* we're now waiting on the lock, but no longer actively locking */
count = rwsem_atomic_update(adjustment, sem);
@@ -205,7 +207,7 @@ rwsem_down_failed_common(struct rw_semaphore *sem,

/* wait to be given the lock */
for (;;) {
- if (!waiter->task)
+ if (!waiter.task)
break;
schedule();
set_task_state(tsk, TASK_UNINTERRUPTIBLE);
@@ -222,11 +224,8 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
asmregparm struct rw_semaphore __sched *
rwsem_down_read_failed(struct rw_semaphore *sem)
{
- struct rwsem_waiter waiter;
-
- waiter.flags = RWSEM_WAITING_FOR_READ;
- rwsem_down_failed_common(sem, &waiter, -RWSEM_ACTIVE_READ_BIAS);
- return sem;
+ return rwsem_down_failed_common(sem, RWSEM_WAITING_FOR_READ,
+ -RWSEM_ACTIVE_READ_BIAS);
}

/*
@@ -235,12 +234,8 @@ rwsem_down_read_failed(struct rw_semaphore *sem)
asmregparm struct rw_semaphore __sched *
rwsem_down_write_failed(struct rw_semaphore *sem)
{
- struct rwsem_waiter waiter;
-
- waiter.flags = RWSEM_WAITING_FOR_WRITE;
- rwsem_down_failed_common(sem, &waiter, -RWSEM_ACTIVE_WRITE_BIAS);
-
- return sem;
+ return rwsem_down_failed_common(sem, RWSEM_WAITING_FOR_WRITE,
+ -RWSEM_ACTIVE_WRITE_BIAS);
}

/*
--
1.7.0.1

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Prev: [PATCH 04/10] rwsem: let RWSEM_WAITING_BIAS represent any number of waiting threads
Next: [PATCH 07/10] generic rwsem: implement down_read_unfair