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: 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
---
 libgo/go/runtime/proc.go | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'libgo')

diff --git a/libgo/go/runtime/proc.go b/libgo/go/runtime/proc.go
index 1d95109..20fa0ad 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
 	}
 
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