linux-kernel - [PATCH 17/19] sched: Inherit task cookie on fork()

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Date:   Thu, 22 Apr 2021 14:05:16 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     joel@...lfernandes.org, chris.hyser@...cle.com, joshdon@...gle.com,
        mingo@...nel.org, vincent.guittot@...aro.org,
        valentin.schneider@....com, mgorman@...e.de
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        tglx@...utronix.de
Subject: [PATCH 17/19] sched: Inherit task cookie on fork()

Note that sched_core_fork() is called from under tasklist_lock, and
not from sched_fork() earlier. This avoids a few races later.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 include/linux/sched.h     |    2 ++
 kernel/fork.c             |    3 +++
 kernel/sched/core_sched.c |    6 ++++++
 3 files changed, 11 insertions(+)

--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2172,8 +2172,10 @@ const struct cpumask *sched_trace_rd_spa
 
 #ifdef CONFIG_SCHED_CORE
 extern void sched_core_free(struct task_struct *tsk);
+extern void sched_core_fork(struct task_struct *p);
 #else
 static inline void sched_core_free(struct task_struct *tsk) { }
+static inline void sched_core_fork(struct task_struct *p) { }
 #endif
 
 #endif
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2249,6 +2249,8 @@ static __latent_entropy struct task_stru
 
 	klp_copy_process(p);
 
+	sched_core_fork(p);
+
 	spin_lock(&current->sighand->siglock);
 
 	/*
@@ -2336,6 +2338,7 @@ static __latent_entropy struct task_stru
 	return p;
 
 bad_fork_cancel_cgroup:
+	sched_core_free(p);
 	spin_unlock(&current->sighand->siglock);
 	write_unlock_irq(&tasklist_lock);
 	cgroup_cancel_fork(p, args);
--- a/kernel/sched/core_sched.c
+++ b/kernel/sched/core_sched.c
@@ -100,6 +100,12 @@ static unsigned long sched_core_clone_co
 	return cookie;
 }
 
+void sched_core_fork(struct task_struct *p)
+{
+	RB_CLEAR_NODE(&p->core_node);
+	p->core_cookie = sched_core_clone_cookie(current);
+}
+
 void sched_core_free(struct task_struct *p)
 {
 	sched_core_put_cookie(p->core_cookie);