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Commit 5376f2e7 authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Ingo Molnar
Browse files

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: default avatarDavidlohr Bueso <dave@stgolabs.net>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 0039962a

drivers/tty/tty_ldsem.c

+8 −10
Original line number Diff line number Diff line
@@ -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)