runtime: fix saved PC/SP after safe-point function in syscall

Running a safe-point function on syscall entry uses systemstack() and
hence clobbers g.sched.pc and g.sched.sp. Fix this by re-saving them
after the systemstack, just like in the other uses of systemstack in
reentersyscall.

Change-Id: I47868a53eba24d81919fda56ef6bbcf72f1f922e
Reviewed-on: https://go-review.googlesource.com/12125
Reviewed-by: Russ Cox <rsc@golang.org>

diff --git a/src/runtime/proc1.go b/src/runtime/proc1.go
index 6e9bf882253c1804fa9e6d8b58e65e75c51d8765..fccc2ac70fe4d8332b27d1f5308b3a685eeb04af 100644 (file)
--- a/src/runtime/proc1.go
+++ b/src/runtime/proc1.go
@@ -1831,6 +1831,7 @@ func reentersyscall(pc, sp uintptr) {
        if _g_.m.p.ptr().runSafePointFn != 0 {
                // runSafePointFn may stack split if run on this stack
                systemstack(runSafePointFn)
+               save(pc, sp)
        }
 
        _g_.m.syscalltick = _g_.m.p.ptr().syscalltick