This patch adds the CONFIG_PROXY_EXEC option, along with
a boot argument prox_exec= that can be used to disable the
feature at boot time if CONFIG_PROXY_EXEC was enabled.

Cc: Joel Fernandes <joelaf@google.com>
Cc: Qais Yousef <qyousef@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Zimuzo Ezeozue <zezeozue@google.com>
Cc: Youssef Esmat <youssefesmat@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: kernel-team@android.com
Signed-off-by: John Stultz <jstultz@google.com>
---
 .../admin-guide/kernel-parameters.txt         |  4 +++
 include/linux/sched.h                         | 13 ++++++++
 init/Kconfig                                  |  7 +++++
 kernel/sched/core.c                           | 31 +++++++++++++++++++
 4 files changed, 55 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 0a1731a0f0ef..199578ae1606 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4648,6 +4648,10 @@
 			that).
 			Format: <bool>
 
+	proxy_exec=	[KNL] Enable or disables "proxy execution" style
+			solution to mutex based priority inversion.
+			Format: "enable" or "disable"
+
 	psi=		[KNL] Enable or disable pressure stall information
 			tracking.
 			Format: <bool>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 81334677e008..5f05d9a4cc3f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1551,6 +1551,19 @@ struct task_struct {
 	 */
 };
 
+#ifdef CONFIG_PROXY_EXEC
+DECLARE_STATIC_KEY_TRUE(__sched_proxy_exec);
+static inline bool sched_proxy_exec(void)
+{
+	return static_branch_likely(&__sched_proxy_exec);
+}
+#else
+static inline bool sched_proxy_exec(void)
+{
+	return false;
+}
+#endif
+
 static inline struct pid *task_pid(struct task_struct *task)
 {
 	return task->thread_pid;
diff --git a/init/Kconfig b/init/Kconfig
index 6d35728b94b2..884f94d8ee9e 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -908,6 +908,13 @@ config NUMA_BALANCING_DEFAULT_ENABLED
 	  If set, automatic NUMA balancing will be enabled if running on a NUMA
 	  machine.
 
+config PROXY_EXEC
+	bool "Proxy Execution"
+	default n
+	help
+	  This option enables proxy execution, a mechanism for mutex owning
+	  tasks to inherit the scheduling context of higher priority waiters.
+
 menuconfig CGROUPS
 	bool "Control Group support"
 	select KERNFS
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 802551e0009b..a38bf8ef5798 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -117,6 +117,37 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
 
 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
 
+#ifdef CONFIG_PROXY_EXEC
+DEFINE_STATIC_KEY_TRUE(__sched_proxy_exec);
+static int __init setup_proxy_exec(char *str)
+{
+	int ret = 0;
+
+	if (!str)
+		goto out;
+
+	if (!strcmp(str, "enable")) {
+		static_branch_enable(&__sched_proxy_exec);
+		ret = 1;
+	} else if (!strcmp(str, "disable")) {
+		static_branch_disable(&__sched_proxy_exec);
+		ret = 1;
+	}
+out:
+	if (!ret)
+		pr_warn("Unable to parse proxy_exec=\n");
+
+	return ret;
+}
+#else
+static int __init setup_proxy_exec(char *str)
+{
+	pr_warn("CONFIG_PROXY_EXEC=n, so it cannot be enabled or disabled at boottime\n");
+	return 0;
+}
+#endif
+__setup("proxy_exec=", setup_proxy_exec);
+
 #ifdef CONFIG_SCHED_DEBUG
 /*
  * Debugging: various feature bits
-- 
2.42.0.869.gea05f2083d-goog