libgo patch committed: Remove unnecessary Entersyscall (RMs: OK for GCC 5 branch?)

[Ian Lance Taylor]

This patch by Lynn Boger removes unnecessary duplicate calls to
Entersyscall and Exitsyscall from the GNU/Linux Getdents function.
The calls are duplicates because they are called by Syscall, also
called by Getdents.  These duplicate calls sometimes cause the
deadlock detector to fire incorrectly, reported as
http://golang.org/issue/11406 .  This patch fixes that problem.
Bootstrapped and ran Go tests on mainline, GCC 4.9 branch, and GCC 5
branch.  Committed to mainline and 4.9 branch.

Release managers: OK to commit to GCC 5 branch?

Ian

Index: libgo/go/syscall/libcall_linux.go
===================================================================
--- libgo/go/syscall/libcall_linux.go   (revision 225715)
+++ libgo/go/syscall/libcall_linux.go   (working copy)
@@ -223,7 +223,6 @@ func Getdents(fd int, buf []byte) (n int
        } else {
                p = (*byte)(unsafe.Pointer(&_zero))
        }
-       Entersyscall()
        s := SYS_GETDENTS64
        if s == 0 {
                s = SYS_GETDENTS
@@ -233,7 +232,6 @@ func Getdents(fd int, buf []byte) (n int
        if n < 0 {
                err = errno
        }
-       Exitsyscall()
        return
 }