linux-kernel - [RFC PATCH v2 5/5] sched: UMCG: allow to sys_umcg

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Date:   Thu, 13 Jan 2022 15:39:40 -0800
From:   Peter Oskolkov <posk@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>, mingo@...hat.com,
        tglx@...utronix.de, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-api@...r.kernel.org, x86@...nel.org, pjt@...gle.com,
        posk@...gle.com, avagin@...gle.com, jannh@...gle.com,
        tdelisle@...terloo.ca, posk@...k.io
Subject: [RFC PATCH v2 5/5] sched: UMCG: allow to sys_umcg_kick UMCG servers

Add enum umcg_kick_flags:
  @UMCG_KICK_RESCHED: reschedule the task; used for worker preemption
  @UMCG_KICK_TTWU: wake the task; used to wake servers.

It is sometimes useful to wake UMCG servers from the userspace, for
example when a server detects a worker wakeup and wakes an idle server to
run the newly woken worker.

Signed-off-by: Peter Oskolkov <posk@...gle.com>
---
 include/uapi/linux/umcg.h | 10 ++++++++++
 kernel/sched/umcg.c       |  7 +++++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/umcg.h b/include/uapi/linux/umcg.h
index 93fccb44283b..a29e5e91a251 100644
--- a/include/uapi/linux/umcg.h
+++ b/include/uapi/linux/umcg.h
@@ -148,4 +148,14 @@ enum umcg_ctl_flag {
 	UMCG_CTL_WORKER		= 0x10000,
 };
 
+/**
+ * enum umcg_kick_flag - flags to pass to sys_umcg_kick
+ * @UMCG_KICK_RESCHED: reschedule the task; used for worker preemption
+ * @UMCG_KICK_TTWU: wake the task; used to wake servers
+ */
+enum umcg_kick_flag {
+	UMCG_KICK_RESCHED	= 0x001,
+	UMCG_KICK_TTWU		= 0x002,
+};
+
 #endif /* _UAPI_LINUX_UMCG_H */
diff --git a/kernel/sched/umcg.c b/kernel/sched/umcg.c
index b85dec6b82e4..e33ec9eddc3e 100644
--- a/kernel/sched/umcg.c
+++ b/kernel/sched/umcg.c
@@ -669,12 +669,15 @@ SYSCALL_DEFINE2(umcg_kick, u32, flags, pid_t, tid)
 	if (!task)
 		return -ESRCH;
 
-	if (flags)
+	if (flags != UMCG_KICK_RESCHED && flags != UMCG_KICK_TTWU)
 		return -EINVAL;
 
 #ifdef CONFIG_SMP
-	smp_send_reschedule(task_cpu(task));
+	if (flags == UMCG_KICK_RESCHED)
+		smp_send_reschedule(task_cpu(task));
 #endif
+	if (flags == UMCG_KICK_TTWU)
+		try_to_wake_up(task, TASK_NORMAL, 0);
 
 	return 0;
 }
-- 
2.34.1.703.g22d0c6ccf7-goog