linux-kernel - [PATCH v16 03/13] Revert "sched/core: Drop the unused try_get_task

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Date:   Fri,  3 Nov 2017 13:04:42 -0400
From:   Chris Metcalf <cmetcalf@...lanox.com>
To:     Davidlohr Bueso <dave@...olabs.net>,
        Oleg Nesterov <oleg@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Christoph Lameter <cl@...ux.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andy Lutomirski <luto@...capital.net>,
        Michal Hocko <mhocko@...e.com>, linux-kernel@...r.kernel.org
Cc:     Chris Metcalf <cmetcalf@...lanox.com>
Subject: [PATCH v16 03/13] Revert "sched/core: Drop the unused try_get_task_struct() helper function"

This reverts commit f11cc0760b8397e0d230122606421b6a96e9f869.
We do need this function for try_get_task_struct_on_cpu().

Signed-off-by: Chris Metcalf <cmetcalf@...lanox.com>
---
 include/linux/sched/task.h |  2 ++
 kernel/exit.c              | 13 +++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 79a2a744648d..270ff76d43d9 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -96,6 +96,8 @@ static inline void put_task_struct(struct task_struct *t)
 }
 
 struct task_struct *task_rcu_dereference(struct task_struct **ptask);
+struct task_struct *try_get_task_struct(struct task_struct **ptask);
+
 
 #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 f2cd53e92147..e2a3e7458d0f 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -318,6 +318,19 @@ void rcuwait_wake_up(struct rcuwait *w)
 	rcu_read_unlock();
 }
 
+struct task_struct *try_get_task_struct(struct task_struct **ptask)
+{
+	struct task_struct *task;
+
+	rcu_read_lock();
+	task = task_rcu_dereference(ptask);
+	if (task)
+		get_task_struct(task);
+	rcu_read_unlock();
+
+	return task;
+}
+
 /*
  * Determine if a process group is "orphaned", according to the POSIX
  * definition in 2.2.2.52.  Orphaned process groups are not to be affected
-- 
2.1.2