LKML Archive on lore.kernel.org
 help / color / Atom feed
From: tip-bot for Davidlohr Bueso <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: peterz@infradead.org, mingo@kernel.org, tglx@linutronix.de,
	hpa@zytor.com, gregkh@linuxfoundation.org,
	akpm@linux-foundation.org, dave@stgolabs.net,
	torvalds@linux-foundation.org, linux-kernel@vger.kernel.org,
	paulmck@linux.vnet.ibm.com
Subject: [tip:locking/core] drivers/tty: Compute 'current' directly
Date: Sat, 14 Jan 2017 04:30:54 -0800
Message-ID: <tip-5376f2e722026e91cb46384bda8d8b3e9f88217c@git.kernel.org> (raw)
In-Reply-To: <1483479794-14013-3-git-send-email-dave@stgolabs.net>

Commit-ID:  5376f2e722026e91cb46384bda8d8b3e9f88217c
Gitweb:     http://git.kernel.org/tip/5376f2e722026e91cb46384bda8d8b3e9f88217c
Author:     Davidlohr Bueso <dave@stgolabs.net>
AuthorDate: Tue, 3 Jan 2017 13:43:12 -0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Sat, 14 Jan 2017 11:14:13 +0100

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>
---
 drivers/tty/tty_ldsem.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/tty_ldsem.c b/drivers/tty/tty_ldsem.c
index 1bf8ed1..3e67229 100644
--- 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)

  reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-03 21:43 [PATCH 0/4] current vs ptr to current dereferencing Davidlohr Bueso
2017-01-03 21:43 ` [PATCH 1/4] kernel/exit: Compute current directly Davidlohr Bueso
2017-01-14 12:30   ` [tip:locking/core] kernel/exit: Compute 'current' directly tip-bot for Davidlohr Bueso
2017-01-03 21:43 ` [PATCH 2/4] drivers/tty: Compute current directly Davidlohr Bueso
2017-01-14 12:30   ` tip-bot for Davidlohr Bueso [this message]
2017-01-03 21:43 ` [PATCH 3/4] kernel/locking: " Davidlohr Bueso
2017-01-14 12:31   ` [tip:locking/core] kernel/locking: Compute 'current' directly tip-bot for Davidlohr Bueso
2017-01-03 21:43 ` [PATCH 4/4] sched: Remove set_task_state() Davidlohr Bueso
2017-01-14 12:31   ` [tip:locking/core] sched/core: " tip-bot for Davidlohr Bueso
2017-01-04 16:40 ` [PATCH 0/4] current vs ptr to current dereferencing Linus Torvalds
2017-01-05 11:42   ` Peter Zijlstra

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=tip-5376f2e722026e91cb46384bda8d8b3e9f88217c@git.kernel.org \
    --to=tipbot@zytor.com \
    --cc=akpm@linux-foundation.org \
    --cc=dave@stgolabs.net \
    --cc=gregkh@linuxfoundation.org \
    --cc=hpa@zytor.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-tip-commits@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=paulmck@linux.vnet.ibm.com \
    --cc=peterz@infradead.org \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git