[PATCH 04/12] rwsem: consistently use adjustment variable
in [Kernel]
|
Prev: [PATCH 08/12] rwsem: smaller wrappers around rwsem_down_failed_common
Next: [PATCH 06/12] rwsem: wake queued readers when other readers are active
From: Michel Lespinasse on 11 May 2010 23:30 Cleanup: previous change introduced an adjustment variable used in waking writers; the code to wake readers can be made nicer by making use of that same variable. Reducing variable count should hopefully help both humans and compilers looking at this function :) Signed-off-by: Michel Lespinasse <walken(a)google.com> --- lib/rwsem.c | 15 +++++++-------- 1 files changed, 7 insertions(+), 8 deletions(-) diff --git a/lib/rwsem.c b/lib/rwsem.c index 0fb6e38..92c8f8e 100644 --- a/lib/rwsem.c +++ b/lib/rwsem.c @@ -52,7 +52,7 @@ __rwsem_do_wake(struct rw_semaphore *sem, int downgrading) struct rwsem_waiter *waiter; struct task_struct *tsk; struct list_head *next; - signed long oldcount, woken, loop, adjustment; + signed long oldcount, loop, adjustment; waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list); if (!(waiter->flags & RWSEM_WAITING_FOR_WRITE)) @@ -96,9 +96,9 @@ __rwsem_do_wake(struct rw_semaphore *sem, int downgrading) * readers before waking any processes up */ readers_only: - woken = 0; + loop = 0; do { - woken++; + loop++; if (waiter->list.next == &sem->wait_list) break; @@ -108,14 +108,13 @@ __rwsem_do_wake(struct rw_semaphore *sem, int downgrading) } while (waiter->flags & RWSEM_WAITING_FOR_READ); - loop = woken; - woken *= RWSEM_ACTIVE_READ_BIAS; + adjustment = loop * RWSEM_ACTIVE_READ_BIAS; if (waiter->flags & RWSEM_WAITING_FOR_READ) /* hit end of list above */ - woken -= RWSEM_WAITING_BIAS; + adjustment -= RWSEM_WAITING_BIAS; retry_readers: - oldcount = rwsem_atomic_update(woken, sem) - woken; + oldcount = rwsem_atomic_update(adjustment, sem) - adjustment; if (!downgrading && (oldcount & RWSEM_ACTIVE_MASK)) /* Someone grabbed the sem already */ goto undo_readers; @@ -144,7 +143,7 @@ __rwsem_do_wake(struct rw_semaphore *sem, int downgrading) goto retry_writer; undo_readers: - if (rwsem_atomic_update(-woken, sem) & RWSEM_ACTIVE_MASK) + if (rwsem_atomic_update(-adjustment, sem) & RWSEM_ACTIVE_MASK) goto out; goto retry_readers; } -- 1.7.0.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |