The patch titled
Subject: drivers/tty: compute current directly
has been added to the -mm tree. Its filename is
drivers-tty-compute-current-directly.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/drivers-tty-compute-current-directly.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/drivers-tty-compute-current-directly.patch
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------------------------------------------------------
From: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Subject: 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:
https://lkml.org/lkml/2016/12/30/230
Link: http://lkml.kernel.org/r/1483479794-14013-3-git-send-email-dave@xxxxxxxxxxxx
Signed-off-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/tty/tty_ldsem.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)
diff -puN drivers/tty/tty_ldsem.c~drivers-tty-compute-current-directly drivers/tty/tty_ldsem.c
--- a/drivers/tty/tty_ldsem.c~drivers-tty-compute-current-directly
+++ a/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 *se
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 *se
/* 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 *se
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 *s
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 *s
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)
_
Patches currently in -mm which might be from dave@xxxxxxxxxxxx are
kernel-exit-compute-current-directly.patch
drivers-tty-compute-current-directly.patch
kernel-locking-compute-current-directly.patch
sched-remove-set_task_state.patch
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