[PATCH] [semaphore] Removed redundant code from semaphore's down family of function

[Satendra Singh Thakur]

-The semaphore code has four funcs
down,
down_interruptible,
down_killable,
down_timeout
-These four funcs have almost similar code except that
they all call lower level function __down_xyz.
-This lower level func in-turn call inline func
__down_common with appropriate arguments.
-This patch creates a common macro for above family of funcs
so that duplicate code is eliminated.
-Also, __down_common has been made noinline so that code is
functionally similar to previous one
-For example, earlier down_killable would call __down_killable
, which in-turn would call inline func __down_common
Now, down_killable calls noinline __down_common directly
through a macro
-The funcs __down_interruptible, __down_killable etc have been
removed as they were just wrapper to __down_common

Signed-off-by: Satendra Singh Thakur <satendrasingh.thakur@xxxxxxx>
---
 kernel/locking/semaphore.c | 107 +++++++++++++------------------------
 1 file changed, 38 insertions(+), 69 deletions(-)

diff --git a/kernel/locking/semaphore.c b/kernel/locking/semaphore.c
index d9dd94defc0a..0468bc335908 100644
--- a/kernel/locking/semaphore.c
+++ b/kernel/locking/semaphore.c
@@ -33,11 +33,33 @@
 #include <linux/spinlock.h>
 #include <linux/ftrace.h>

-static noinline void __down(struct semaphore *sem);
-static noinline int __down_interruptible(struct semaphore *sem);
-static noinline int __down_killable(struct semaphore *sem);
-static noinline int __down_timeout(struct semaphore *sem, long timeout);
+static noinline int __sched __down_common(struct semaphore *sem, long state,
+long timeout);
 static noinline void __up(struct semaphore *sem);
+/**
+ * down_common - acquire the semaphore
+ * @sem: the semaphore to be acquired
+ * @state: new state of the task
+ * @timeout: either MAX_SCHEDULE_TIMEOUT or actual specified
+ * timeout
+ * Acquires the semaphore. If no more tasks are allowed to
+ * acquire the semaphore, calling this macro will put the task
+ * to sleep until the semaphore is released.
+ *
+ * This internally calls another func __down_common.
+ */
+#define down_common(sem, state, timeout)\
+({\
+int ret = 0;\
+unsigned long flags;\
+raw_spin_lock_irqsave(&(sem)->lock, flags);\
+if (likely((sem)->count > 0))\
+(sem)->count--;\
+else\
+ret = __down_common(sem, state, timeout);\
+raw_spin_unlock_irqrestore(&(sem)->lock, flags);\
+ret;\
+})

 /**
  * down - acquire the semaphore
@@ -52,14 +74,7 @@ static noinline void __up(struct semaphore *sem);
  */
 void down(struct semaphore *sem)
 {
-unsigned long flags;
-
-raw_spin_lock_irqsave(&sem->lock, flags);
-if (likely(sem->count > 0))
-sem->count--;
-else
-__down(sem);
-raw_spin_unlock_irqrestore(&sem->lock, flags);
+down_common(sem, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 }
 EXPORT_SYMBOL(down);

@@ -74,17 +89,7 @@ EXPORT_SYMBOL(down);
  */
 int down_interruptible(struct semaphore *sem)
 {
-unsigned long flags;
-int result = 0;
-
-raw_spin_lock_irqsave(&sem->lock, flags);
-if (likely(sem->count > 0))
-sem->count--;
-else
-result = __down_interruptible(sem);
-raw_spin_unlock_irqrestore(&sem->lock, flags);
-
-return result;
+return down_common(sem, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 }
 EXPORT_SYMBOL(down_interruptible);

@@ -100,17 +105,7 @@ EXPORT_SYMBOL(down_interruptible);
  */
 int down_killable(struct semaphore *sem)
 {
-unsigned long flags;
-int result = 0;
-
-raw_spin_lock_irqsave(&sem->lock, flags);
-if (likely(sem->count > 0))
-sem->count--;
-else
-result = __down_killable(sem);
-raw_spin_unlock_irqrestore(&sem->lock, flags);
-
-return result;
+return down_common(sem, TASK_KILLABLE, MAX_SCHEDULE_TIMEOUT);
 }
 EXPORT_SYMBOL(down_killable);

@@ -154,17 +149,7 @@ EXPORT_SYMBOL(down_trylock);
  */
 int down_timeout(struct semaphore *sem, long timeout)
 {
-unsigned long flags;
-int result = 0;
-
-raw_spin_lock_irqsave(&sem->lock, flags);
-if (likely(sem->count > 0))
-sem->count--;
-else
-result = __down_timeout(sem, timeout);
-raw_spin_unlock_irqrestore(&sem->lock, flags);
-
-return result;
+return down_common(sem, TASK_UNINTERRUPTIBLE, timeout);
 }
 EXPORT_SYMBOL(down_timeout);

@@ -196,12 +181,15 @@ struct semaphore_waiter {
 bool up;
 };

-/*
- * Because this function is inlined, the 'state' parameter will be
- * constant, and thus optimised away by the compiler.  Likewise the
- * 'timeout' parameter for the cases without timeouts.
+/**
+ * __down_common - Adds the current task to wait list
+ * puts the task to sleep until signal, timeout or up flag
+ * @sem: the semaphore to be acquired
+ * @state: the state of the calling task
+ * @timeout: either MAX_SCHEDULE_TIMEOUT or actual specified
+ * timeout
  */
-static inline int __sched __down_common(struct semaphore *sem, long state,
+static noinline int __sched __down_common(struct semaphore *sem, long state,
 long timeout)
 {
 struct semaphore_waiter waiter;
@@ -232,25 +220,6 @@ static inline int __sched __down_common(struct semaphore *sem, long state,
 return -EINTR;
 }

-static noinline void __sched __down(struct semaphore *sem)
-{
-__down_common(sem, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
-}
-
-static noinline int __sched __down_interruptible(struct semaphore *sem)
-{
-return __down_common(sem, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
-}
-
-static noinline int __sched __down_killable(struct semaphore *sem)
-{
-return __down_common(sem, TASK_KILLABLE, MAX_SCHEDULE_TIMEOUT);
-}
-
-static noinline int __sched __down_timeout(struct semaphore *sem, long timeout)
-{
-return __down_common(sem, TASK_UNINTERRUPTIBLE, timeout);
-}

 static noinline void __sched __up(struct semaphore *sem)
 {
--
2.17.1

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