From 911cef2e3ba7548ee13e761f88457c6bbe1fa7fe Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <ian@gcc.gnu.org>
Date: Tue, 20 Feb 2018 15:30:31 +0000
Subject: [PATCH] runtime: allow preemption in fast syscall return

    Let a fast syscall return be a preemption point.  This helps with
    tight loops that make system calls, as in BenchmarkSyscallExcessWork.

    Reviewed-on: https://go-review.googlesource.com/94895

From-SVN: r257848
---
 gcc/go/gofrontend/MERGE  | 2 +-
 libgo/go/runtime/proc.go | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index 61bed68afca..c52bf4e0dc0 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-459a8a94e04a19bde7173ef7cf2db369c2e62e2d
+c6e0970f75508e209a10a7db5164d6ea3f9b28bf
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/libgo/go/runtime/proc.go b/libgo/go/runtime/proc.go
index 1d95109d7c0..20fa0ad05be 100644
--- a/libgo/go/runtime/proc.go
+++ b/libgo/go/runtime/proc.go
@@ -2794,6 +2794,13 @@ func exitsyscall(dummy int32) {
 		exitsyscallclear(_g_)
 		_g_.m.locks--
 		_g_.throwsplit = false
+
+		// Check preemption, since unlike gc we don't check on
+		// every call.
+		if getg().preempt {
+			checkPreempt()
+		}
+
 		return
 	}