[PATCH RT 04/39] rtmutex: No need to keep task ref for lock owner check

From: Steven Rostedt
Date: Thu Mar 12 2015 - 15:43:12 EST

3.14.34-rt32-rc1 stable review patch.
If anyone has any objections, please let me know.


From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

upstream commit: 2ffa5a5cd2fe792b6399c903d5172adf088d8ff7

There is no point to keep the task ref across the check for lock
owner. Drop the ref before that, so the protection context is clear.

Found while documenting the chain walk.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Reviewed-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
kernel/locking/rtmutex.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index e4cbd0cd5405..901a29345451 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -484,6 +484,8 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,

/* Release the task */
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
+ put_task_struct(task);
if (!rt_mutex_owner(lock)) {
struct rt_mutex_waiter *lock_top_waiter;

@@ -495,9 +497,8 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
if (top_waiter != lock_top_waiter)
- goto out_put_task;
+ return 0;
- put_task_struct(task);

/* Grab the next task */
task = rt_mutex_owner(lock);

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