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From:   "Joel Fernandes (Google)" <joel@joelfernandes.org>
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        Julien Desfossez <jdesfossez@digitalocean.com>,
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        Tim Chen <tim.c.chen@intel.com>
Subject: [PATCH v8 -tip 20/26] sched: Release references to the per-task cookie on exit
Date:   Mon, 19 Oct 2020 21:43:30 -0400
Message-Id: <20201020014336.2076526-21-joel@joelfernandes.org>
In-Reply-To: <20201020014336.2076526-1-joel@joelfernandes.org>
References: <20201020014336.2076526-1-joel@joelfernandes.org>
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During exit, we have to free the references to a cookie that might be shared by
many tasks. This commit therefore ensures when the task_struct is released, any
references to cookies that it holds are also released.

Tested-by: Julien Desfossez <jdesfossez@digitalocean.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 include/linux/sched.h | 2 ++
 kernel/fork.c         | 1 +
 kernel/sched/core.c   | 8 ++++++++
 3 files changed, 11 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4cb76575afa8..eabd96beff92 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2079,12 +2079,14 @@ void sched_core_unsafe_exit(void);
 bool sched_core_wait_till_safe(unsigned long ti_check);
 bool sched_core_kernel_protected(void);
 int sched_core_share_pid(pid_t pid);
+void sched_tsk_free(struct task_struct *tsk);
 #else
 #define sched_core_unsafe_enter(ignore) do { } while (0)
 #define sched_core_unsafe_exit(ignore) do { } while (0)
 #define sched_core_wait_till_safe(ignore) do { } while (0)
 #define sched_core_kernel_protected(ignore) do { } while (0)
 #define sched_core_share_pid(pid_t pid) do { } while (0)
+#define sched_tsk_free(tsk) do { } while (0)
 #endif
 
 #endif
diff --git a/kernel/fork.c b/kernel/fork.c
index b9c289d0f4ef..a39248a02fdd 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -736,6 +736,7 @@ void __put_task_struct(struct task_struct *tsk)
 	exit_creds(tsk);
 	delayacct_tsk_free(tsk);
 	put_signal_struct(tsk->signal);
+	sched_tsk_free(tsk);
 
 	if (!profile_handoff_task(tsk))
 		free_task(tsk);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 42aa811eab14..61e1dcf11000 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9631,6 +9631,14 @@ static int cpu_core_tag_color_write_u64(struct cgroup_subsys_state *css,
 
 	return 0;
 }
+
+void sched_tsk_free(struct task_struct *tsk)
+{
+	if (!tsk->core_task_cookie)
+		return;
+	sched_core_put_task_cookie(tsk->core_task_cookie);
+	sched_core_put();
+}
 #endif
 
 static struct cftype cpu_legacy_files[] = {
-- 
2.29.0.rc1.297.gfa9743e501-goog