drivers/tty: Compute 'current' directly

This patch effectively replaces the tsk pointer dereference
(which is obviously == current), to directly use get_current()
macro. This is to make the removal of setting foreign task
states smoother and painfully obvious. Performance win on some
archs such as x86-64 and ppc64 -- arm64 is no longer an issue.

Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: mark.rutland@arm.com
Link: http://lkml.kernel.org/r/1483479794-14013-3-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/drivers/tty/tty_ldsem.c b/drivers/tty/tty_ldsem.c
index 1bf8ed13f82708d417cfc8ff9d670d46a674ee35..3e6722954f29ee7f6fe7b5a4c014d08ae566540b 100644 (file)
--- a/drivers/tty/tty_ldsem.c
+++ b/drivers/tty/tty_ldsem.c
@@ -200,7 +200,6 @@ static struct ld_semaphore __sched *
 down_read_failed(struct ld_semaphore *sem, long count, long timeout)
 {
        struct ldsem_waiter waiter;
-       struct task_struct *tsk = current;
        long adjust = -LDSEM_ACTIVE_BIAS + LDSEM_WAIT_BIAS;
 
        /* set up my own style of waitqueue */
@@ -221,8 +220,8 @@ down_read_failed(struct ld_semaphore *sem, long count, long timeout)
        list_add_tail(&waiter.list, &sem->read_wait);
        sem->wait_readers++;
 
-       waiter.task = tsk;
-       get_task_struct(tsk);
+       waiter.task = current;
+       get_task_struct(current);
 
        /* if there are no active locks, wake the new lock owner(s) */
        if ((count & LDSEM_ACTIVE_MASK) == 0)
@@ -232,7 +231,7 @@ down_read_failed(struct ld_semaphore *sem, long count, long timeout)
 
        /* wait to be given the lock */
        for (;;) {
-               set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+               set_task_state(current, TASK_UNINTERRUPTIBLE);
 
                if (!waiter.task)
                        break;
@@ -241,7 +240,7 @@ down_read_failed(struct ld_semaphore *sem, long count, long timeout)
                timeout = schedule_timeout(timeout);
        }
 
-       __set_task_state(tsk, TASK_RUNNING);
+       __set_task_state(current, TASK_RUNNING);
 
        if (!timeout) {
                /* lock timed out but check if this task was just
@@ -268,7 +267,6 @@ static struct ld_semaphore __sched *
 down_write_failed(struct ld_semaphore *sem, long count, long timeout)
 {
        struct ldsem_waiter waiter;
-       struct task_struct *tsk = current;
        long adjust = -LDSEM_ACTIVE_BIAS;
        int locked = 0;
 
@@ -289,16 +287,16 @@ down_write_failed(struct ld_semaphore *sem, long count, long timeout)
 
        list_add_tail(&waiter.list, &sem->write_wait);
 
-       waiter.task = tsk;
+       waiter.task = current;
 
-       set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+       set_task_state(current, TASK_UNINTERRUPTIBLE);
        for (;;) {
                if (!timeout)
                        break;
                raw_spin_unlock_irq(&sem->wait_lock);
                timeout = schedule_timeout(timeout);
                raw_spin_lock_irq(&sem->wait_lock);
-               set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+               set_task_state(current, TASK_UNINTERRUPTIBLE);
                locked = writer_trylock(sem);
                if (locked)
                        break;
@@ -309,7 +307,7 @@ down_write_failed(struct ld_semaphore *sem, long count, long timeout)
        list_del(&waiter.list);
        raw_spin_unlock_irq(&sem->wait_lock);
 
-       __set_task_state(tsk, TASK_RUNNING);
+       __set_task_state(current, TASK_RUNNING);
 
        /* lock wait may have timed out */
        if (!locked)