linux-kernel - [tip:sched/core] Revert "kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live

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Date:   Thu, 8 Dec 2016 05:43:36 -0800
From:   tip-bot for Oleg Nesterov <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     mingo@...nel.org, oleg@...hat.com, hpa@...or.com, pmladek@...e.com,
        roman.penyaev@...fitbricks.com, akpm@...ux-foundation.org,
        tglx@...utronix.de, tj@...nel.org, David1.Zhou@....com,
        peterz@...radead.org, luto@...capital.net,
        linux-kernel@...r.kernel.org, luto@...nel.org,
        alexander.deucher@....com
Subject: [tip:sched/core] Revert "kthread: Pin the stack via
 try_get_task_stack()/put_task_stack() in to_live_kthread() function"

Commit-ID:  eff9662547f358239b98dfc4a8e6905b494e14d6
Gitweb:     http://git.kernel.org/tip/eff9662547f358239b98dfc4a8e6905b494e14d6
Author:     Oleg Nesterov <oleg@...hat.com>
AuthorDate: Tue, 29 Nov 2016 18:51:00 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Thu, 8 Dec 2016 14:36:18 +0100

Revert "kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live_kthread() function"

This reverts commit 23196f2e5f5d810578a772785807dcdc2b9fdce9.

Now that struct kthread is kmalloc'ed and not longer on the task stack
there is no need anymore to pin the stack.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Chunming Zhou <David1.Zhou@....com>
Cc: Roman Pen <roman.penyaev@...fitbricks.com>
Cc: Petr Mladek <pmladek@...e.com>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Tejun Heo <tj@...nel.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Alex Deucher <alexander.deucher@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Link: http://lkml.kernel.org/r/20161129175100.GA5333@redhat.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 kernel/kthread.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 9d64b65..7891a94 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -88,7 +88,7 @@ void free_kthread_struct(struct task_struct *k)
 static struct kthread *to_live_kthread(struct task_struct *k)
 {
 	struct completion *vfork = ACCESS_ONCE(k->vfork_done);
-	if (likely(vfork) && try_get_task_stack(k))
+	if (likely(vfork))
 		return __to_kthread(vfork);
 	return NULL;
 }
@@ -473,10 +473,8 @@ void kthread_unpark(struct task_struct *k)
 {
 	struct kthread *kthread = to_live_kthread(k);
 
-	if (kthread) {
+	if (kthread)
 		__kthread_unpark(k, kthread);
-		put_task_stack(k);
-	}
 }
 EXPORT_SYMBOL_GPL(kthread_unpark);
 
@@ -505,7 +503,6 @@ int kthread_park(struct task_struct *k)
 				wait_for_completion(&kthread->parked);
 			}
 		}
-		put_task_stack(k);
 		ret = 0;
 	}
 	return ret;
@@ -541,7 +538,6 @@ int kthread_stop(struct task_struct *k)
 		__kthread_unpark(k, kthread);
 		wake_up_process(k);
 		wait_for_completion(&kthread->exited);
-		put_task_stack(k);
 	}
 	ret = k->exit_code;
 	put_task_struct(k);