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Subject[PATCH 4/6] Introduce down_killable()
Date
down_killable() is the functional counterpart of mutex_lock_killable.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
---
include/linux/semaphore.h | 6 ++++++
kernel/semaphore.c | 22 ++++++++++++++++++++++
2 files changed, 28 insertions(+), 0 deletions(-)

diff --git a/include/linux/semaphore.h b/include/linux/semaphore.h
index b3c691b..88f2a28 100644
--- a/include/linux/semaphore.h
+++ b/include/linux/semaphore.h
@@ -62,6 +62,12 @@ extern void down(struct semaphore *sem);
extern int __must_check down_interruptible(struct semaphore *sem);

/*
+ * As down_interruptible(), except the sleep may only be interrupted by
+ * signals which are fatal to this process.
+ */
+extern int __must_check down_killable(struct semaphore *sem);
+
+/*
* As down(), except this function will not sleep. It will return 0 if it
* acquired the semaphore and 1 if the semaphore was contended. This
* function may be called from any context, including interrupt and softirq.
diff --git a/kernel/semaphore.c b/kernel/semaphore.c
index d5a7270..2da2aed 100644
--- a/kernel/semaphore.c
+++ b/kernel/semaphore.c
@@ -34,6 +34,7 @@

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 void __up(struct semaphore *sem);

void down(struct semaphore *sem)
@@ -61,6 +62,20 @@ int down_interruptible(struct semaphore *sem)
}
EXPORT_SYMBOL(down_interruptible);

+int down_killable(struct semaphore *sem)
+{
+ unsigned long flags;
+ int result = 0;
+
+ spin_lock_irqsave(&sem->lock, flags);
+ if (unlikely(sem->count-- <= 0))
+ result = __down_killable(sem);
+ spin_unlock_irqrestore(&sem->lock, flags);
+
+ return result;
+}
+EXPORT_SYMBOL(down_killable);
+
/**
* down_trylock - try to acquire the semaphore, without waiting
* @sem: the semaphore to be acquired
@@ -143,6 +158,8 @@ static inline int __sched __down_common(struct semaphore *sem, long state)
for (;;) {
if (state == TASK_INTERRUPTIBLE && signal_pending(task))
goto interrupted;
+ if (state == TASK_KILLABLE && fatal_signal_pending(task))
+ goto interrupted;
__set_task_state(task, state);
spin_unlock_irq(&sem->lock);
schedule();
@@ -178,6 +195,11 @@ static noinline int __sched __down_interruptible(struct semaphore *sem)
return __down_common(sem, TASK_INTERRUPTIBLE);
}

+static noinline int __sched __down_killable(struct semaphore *sem)
+{
+ return __down_common(sem, TASK_KILLABLE);
+}
+
static noinline void __sched __up(struct semaphore *sem)
{
if (unlikely(list_empty(&sem->wait_list)))
--
1.5.4.3


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