From: ebiederm@xmission.com (Eric W. Biederman)
To: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Oleg Nesterov <oleg@redhat.com>,
Russell King - ARM Linux admin <linux@armlinux.org.uk>,
Chris Metcalf <cmetcalf@ezchip.com>,
Christoph Lameter <cl@linux.com>, Kirill Tkhai <tkhai@yandex.ru>,
Mike Galbraith <efault@gmx.de>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
Davidlohr Bueso <dave@stgolabs.net>
Subject: [PATCH v2 1/4] task: Add a count of task rcu users
Date: Sat, 14 Sep 2019 07:31:13 -0500 [thread overview]
Message-ID: <87h85ff4a6.fsf_-_@x220.int.ebiederm.org> (raw)
In-Reply-To: <87k1apqqgk.fsf@x220.int.ebiederm.org> (Eric W. Biederman's message of "Tue, 03 Sep 2019 11:44:59 -0500")
Add a count of the number of rcu users (currently 1) of the task
struct so that we can later add the scheduler case and get rid of the
very subtle task_rcu_dereference, and just use rcu_dereference.
As suggested by Oleg have the count overlap rcu_head so that no
additional space in task_struct is required.
Inspired-by: Linus Torvalds <torvalds@linux-foundation.org>
Inspired-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
include/linux/sched.h | 5 ++++-
include/linux/sched/task.h | 1 +
kernel/exit.c | 7 ++++++-
kernel/fork.c | 7 +++----
4 files changed, 14 insertions(+), 6 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9f51932bd543..99a4518b9b17 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1142,7 +1142,10 @@ struct task_struct {
struct tlbflush_unmap_batch tlb_ubc;
- struct rcu_head rcu;
+ union {
+ refcount_t rcu_users;
+ struct rcu_head rcu;
+ };
/* Cache last used pipe for splice(): */
struct pipe_inode_info *splice_pipe;
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 0497091e40c1..4c44c37236b2 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -116,6 +116,7 @@ static inline void put_task_struct(struct task_struct *t)
}
struct task_struct *task_rcu_dereference(struct task_struct **ptask);
+void put_task_struct_rcu_user(struct task_struct *task);
#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
extern int arch_task_struct_size __read_mostly;
diff --git a/kernel/exit.c b/kernel/exit.c
index 5b4a5dcce8f8..2e259286f4e7 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -182,6 +182,11 @@ static void delayed_put_task_struct(struct rcu_head *rhp)
put_task_struct(tsk);
}
+void put_task_struct_rcu_user(struct task_struct *task)
+{
+ if (refcount_dec_and_test(&task->rcu_users))
+ call_rcu(&task->rcu, delayed_put_task_struct);
+}
void release_task(struct task_struct *p)
{
@@ -222,7 +227,7 @@ void release_task(struct task_struct *p)
write_unlock_irq(&tasklist_lock);
release_thread(p);
- call_rcu(&p->rcu, delayed_put_task_struct);
+ put_task_struct_rcu_user(p);
p = leader;
if (unlikely(zap_leader))
diff --git a/kernel/fork.c b/kernel/fork.c
index 2852d0e76ea3..9f04741d5c70 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -900,10 +900,9 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
if (orig->cpus_ptr == &orig->cpus_mask)
tsk->cpus_ptr = &tsk->cpus_mask;
- /*
- * One for us, one for whoever does the "release_task()" (usually
- * parent)
- */
+ /* One for the user space visible state that goes away when reaped. */
+ refcount_set(&tsk->rcu_users, 1);
+ /* One for the rcu users, and one for the scheduler */
refcount_set(&tsk->usage, 2);
#ifdef CONFIG_BLK_DEV_IO_TRACE
tsk->btrace_seq = 0;
--
2.21.0.dirty
next prev parent reply other threads:[~2019-09-14 12:31 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-30 14:08 [BUG] Use of probe_kernel_address() in task_rcu_dereference() without checking return value Russell King - ARM Linux admin
2019-08-30 15:24 ` Oleg Nesterov
2019-08-30 15:30 ` Linus Torvalds
2019-08-30 15:40 ` Russell King - ARM Linux admin
2019-08-30 15:43 ` Linus Torvalds
2019-08-30 15:41 ` Linus Torvalds
2019-08-30 16:09 ` Oleg Nesterov
2019-08-30 16:21 ` Linus Torvalds
2019-08-30 16:44 ` Oleg Nesterov
2019-08-30 16:58 ` Linus Torvalds
2019-08-30 19:36 ` Eric W. Biederman
2019-09-02 13:40 ` Oleg Nesterov
2019-09-02 13:53 ` Peter Zijlstra
2019-09-02 14:44 ` Oleg Nesterov
2019-09-02 16:20 ` Peter Zijlstra
2019-09-02 17:04 ` Eric W. Biederman
2019-09-02 17:34 ` Linus Torvalds
2019-09-03 4:50 ` [PATCH 0/3] task: Making tasks on the runqueue rcu protected Eric W. Biederman
2019-09-03 4:51 ` [PATCH 1/3] task: Add a count of task rcu users Eric W. Biederman
2019-09-04 14:36 ` Oleg Nesterov
2019-09-04 14:44 ` Frederic Weisbecker
2019-09-04 15:32 ` Oleg Nesterov
2019-09-04 16:33 ` Frederic Weisbecker
2019-09-04 18:20 ` Linus Torvalds
2019-09-05 14:59 ` Frederic Weisbecker
2019-09-03 4:52 ` [PATCH 2/3] task: RCU protect tasks on the runqueue Eric W. Biederman
2019-09-03 7:41 ` Peter Zijlstra
2019-09-03 7:47 ` Peter Zijlstra
2019-09-03 16:44 ` Eric W. Biederman
2019-09-03 17:08 ` Linus Torvalds
2019-09-03 18:13 ` Eric W. Biederman
2019-09-03 19:18 ` Linus Torvalds
2019-09-03 20:06 ` Peter Zijlstra
2019-09-03 21:32 ` Paul E. McKenney
2019-09-05 20:02 ` Eric W. Biederman
2019-09-05 20:55 ` Paul E. McKenney
2019-09-06 7:07 ` Peter Zijlstra
2019-09-09 12:22 ` Eric W. Biederman
2019-09-25 7:36 ` Peter Zijlstra
2019-09-27 8:10 ` [tip: sched/urgent] tasks, sched/core: RCUify the assignment of rq->curr tip-bot2 for Eric W. Biederman
2019-09-03 19:42 ` [PATCH 2/3] task: RCU protect tasks on the runqueue Peter Zijlstra
2019-09-14 12:31 ` Eric W. Biederman [this message]
2019-09-14 12:31 ` [PATCH v2 2/4] task: Ensure tasks are available for a grace period after leaving " Eric W. Biederman
2019-09-14 12:32 ` [PATCH v2 3/4] task: With a grace period after finish_task_switch, remove unnecessary code Eric W. Biederman
2019-09-04 14:22 ` [PATCH 2/3] task: RCU protect tasks on the runqueue Frederic Weisbecker
2019-09-03 4:52 ` [PATCH 3/3] task: Clean house now that tasks on the runqueue are rcu protected Eric W. Biederman
2019-09-03 9:45 ` kbuild test robot
2019-09-03 13:06 ` Oleg Nesterov
2019-09-03 13:58 ` [PATCH 0/3] task: Making tasks on the runqueue " Oleg Nesterov
2019-09-03 15:44 ` Linus Torvalds
2019-09-03 19:46 ` Peter Zijlstra
[not found] ` <87muf7f4bf.fsf_-_@x220.int.ebiederm.org>
2019-09-14 12:33 ` [PATCH v2 1/4] task: Add a count of task rcu users Eric W. Biederman
2019-09-15 13:54 ` Paul E. McKenney
2019-09-27 8:10 ` [tip: sched/urgent] tasks: Add a count of task RCU users tip-bot2 for Eric W. Biederman
2019-09-14 12:33 ` [PATCH v2 2/4] task: Ensure tasks are available for a grace period after leaving the runqueue Eric W. Biederman
2019-09-15 14:07 ` Paul E. McKenney
2019-09-15 14:09 ` Paul E. McKenney
2019-09-27 8:10 ` [tip: sched/urgent] tasks, sched/core: " tip-bot2 for Eric W. Biederman
2019-09-14 12:34 ` [PATCH v2 3/4] task: With a grace period after finish_task_switch, remove unnecessary code Eric W. Biederman
2019-09-15 14:32 ` Paul E. McKenney
2019-09-15 17:07 ` Linus Torvalds
2019-09-15 18:47 ` Paul E. McKenney
2019-09-27 8:10 ` [tip: sched/urgent] tasks, sched/core: With a grace period after finish_task_switch(), " tip-bot2 for Eric W. Biederman
2019-09-14 12:35 ` [PATCH v2 4/4] task: RCUify the assignment of rq->curr Eric W. Biederman
2019-09-15 14:41 ` Paul E. McKenney
2019-09-15 17:59 ` Eric W. Biederman
2019-09-15 18:25 ` Eric W. Biederman
2019-09-15 18:48 ` Paul E. McKenney
2019-09-20 23:02 ` Frederic Weisbecker
2019-09-26 1:49 ` Eric W. Biederman
2019-09-26 12:42 ` Frederic Weisbecker
2019-09-14 17:43 ` [PATCH v2 0/4] task: Making tasks on the runqueue rcu protected Linus Torvalds
2019-09-17 17:38 ` Eric W. Biederman
2019-09-25 7:51 ` Peter Zijlstra
2019-09-26 1:11 ` Eric W. Biederman
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=87h85ff4a6.fsf_-_@x220.int.ebiederm.org \
--to=ebiederm@xmission.com \
--cc=cl@linux.com \
--cc=cmetcalf@ezchip.com \
--cc=dave@stgolabs.net \
--cc=efault@gmx.de \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=tkhai@yandex.ru \
--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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).