From e3927a0b950bbb60fbb48069d035a16f30140375 Mon Sep 17 00:00:00 2001
From: Masamichi Takagi <masamichi.takagi@riken.jp>
Date: Fri, 5 Feb 2021 09:39:07 +0900
Subject: [PATCH] uti: futex: McKernel waker sends IPI to Linux waiter CPU

Change-Id: I6f725b3a6b1b26b9f553d8c58132c0c0a4416683
---
 executer/kernel/mcctrl/futex.c         |  1 +
 executer/kernel/mcctrl/include/futex.h |  3 +++
 kernel/futex.c                         | 19 +++++++++++++++----
 kernel/host.c                          |  2 +-
 kernel/include/futex.h                 |  3 +++
 5 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/executer/kernel/mcctrl/futex.c b/executer/kernel/mcctrl/futex.c
index 060f90bb..9d887f9d 100644
--- a/executer/kernel/mcctrl/futex.c
+++ b/executer/kernel/mcctrl/futex.c
@@ -813,6 +813,7 @@ static int futex_wait(uint32_t __user *uaddr, int fshared,
 	q->bitset = bitset;
 	q->requeue_pi_key = NULL;
 	q->uti_futex_resp = uti_info->uti_futex_resp;
+	q->linux_cpu = ihk_ikc_get_processor_id();
 
 retry:
 	/* Prepare to wait on uaddr. */
diff --git a/executer/kernel/mcctrl/include/futex.h b/executer/kernel/mcctrl/include/futex.h
index 3ab83081..317f449a 100644
--- a/executer/kernel/mcctrl/include/futex.h
+++ b/executer/kernel/mcctrl/include/futex.h
@@ -140,6 +140,9 @@ struct futex_q {
 	/* Used to wake-up a thread running on a Linux CPU */
 	void *uti_futex_resp;
 
+	/* Used to send IPI directly to the waiter CPU */
+	int linux_cpu;
+
 	/* Used to wake-up a thread running on a McKernel from Linux */
 	void *th_spin_sleep;
 	void *th_status;
diff --git a/kernel/futex.c b/kernel/futex.c
index 7b5a91f9..fb47db78 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -73,12 +73,15 @@
 #include <ihk/debug.h>
 #include <syscall.h>
 #include <kmalloc.h>
+#include <ikc/queue.h>
 
 
 unsigned long ihk_mc_get_ns_per_tsc(void);
 
 struct futex_hash_bucket *futex_queues;
 
+extern struct ihk_ikc_channel_desc **ikc2linuxs;
+
 struct futex_hash_bucket *get_futex_queues(void)
 {
 	return futex_queues;
@@ -238,11 +241,19 @@ static void wake_futex(struct futex_q *q)
 
 	if (q->uti_futex_resp) { 
 		int rc;
-		dkprintf("%s: waking up migrated-to-Linux thread (tid %d),uti_futex_resp=%p\n",
-			__func__, p->tid, q->uti_futex_resp);
-
 		struct ikc_scd_packet pckt;
-		struct ihk_ikc_channel_desc *resp_channel = cpu_local_var(ikc2linux);
+		struct ihk_ikc_channel_desc *resp_channel;
+
+		dkprintf("%s: waking up migrated-to-Linux thread (tid %d),uti_futex_resp=%p,linux_cpu: %d\n",
+			__func__, p->tid, q->uti_futex_resp, q->linux_cpu);
+
+		/* does this Linux CPU have a connected channel? */
+		if (ikc2linuxs[q->linux_cpu]) {
+			resp_channel = ikc2linuxs[q->linux_cpu];
+		} else {
+			resp_channel = cpu_local_var(ikc2linux);
+		}
+
 		pckt.msg = SCD_MSG_FUTEX_WAKE;
 		pckt.futex.resp = q->uti_futex_resp;
 		pckt.futex.spin_sleep = &p->spin_sleep;
diff --git a/kernel/host.c b/kernel/host.c
index 64f6a7b6..05766ad9 100644
--- a/kernel/host.c
+++ b/kernel/host.c
@@ -43,7 +43,7 @@
 #endif
 
 /* Linux channel table, indexec by Linux CPU id */
-static struct ihk_ikc_channel_desc **ikc2linuxs = NULL;
+struct ihk_ikc_channel_desc **ikc2linuxs;
 
 void check_mapping_for_proc(struct thread *thread, unsigned long addr)
 {
diff --git a/kernel/include/futex.h b/kernel/include/futex.h
index 5eb047a8..14b9012e 100644
--- a/kernel/include/futex.h
+++ b/kernel/include/futex.h
@@ -216,6 +216,9 @@ struct futex_q {
 	/* Used to wake-up a thread running on a Linux CPU */
 	void *uti_futex_resp;
 
+	/* Used to send IPI directly to the waiter CPU */
+	int linux_cpu;
+
 	/* Used to wake-up a thread running on a McKernel from Linux */
 	void *th_spin_sleep;
 	void *th_status;