From d4056acfc34a9a247ea1165abd72aaef9e07155f Mon Sep 17 00:00:00 2001
From: Masamichi Takagi <masamichi.takagi@riken.jp>
Date: Mon, 15 Jun 2020 12:58:28 +0900
Subject: [PATCH] epoll, ppoll: deschedule on offload, don't do it when exiting
 system call

Change-Id: Ib1d0553ca5c50f4de055a1a5fe40b406c9c26dc7
---
 kernel/syscall.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/syscall.c b/kernel/syscall.c
index 310d7fc1..f8f5225a 100644
--- a/kernel/syscall.c
+++ b/kernel/syscall.c
@@ -243,7 +243,8 @@ long do_syscall(struct syscall_request *req, int cpu)
 			DECLARE_WAITQ_ENTRY(scd_wq_entry, cpu_local_var(current));
 
 			if (req->number == __NR_epoll_wait ||
-				req->number == __NR_epoll_pwait)
+				req->number == __NR_epoll_pwait ||
+				req->number == __NR_ppoll)
 				goto schedule;
 
 			cpu_pause();
@@ -10280,7 +10281,11 @@ long syscall(int num, ihk_mc_user_context_t *ctx)
 	}
 #endif // PROFILE_ENABLE
 
-	if (smp_load_acquire(&v->flags) & CPU_FLAG_NEED_RESCHED) {
+	/* Do not deschedule when returning from an event (e.g., MPI) */
+	if (!(num == __NR_epoll_wait ||
+				num == __NR_epoll_pwait ||
+				num == __NR_ppoll) &&
+			smp_load_acquire(&v->flags) & CPU_FLAG_NEED_RESCHED) {
 		check_need_resched();
 	}