kernel/signal.c: unexport sigsuspend()

commit 9d8a765211335cfdad464b90fb19f546af5706ae upstream.

sigsuspend() is nowhere used except in signal.c itself, so we can mark it
static do not pollute the global namespace.

But this patch is more than a boring cleanup patch, it fixes a real issue
on UserModeLinux.  UML has a special console driver to display ttys using
xterm, or other terminal emulators, on the host side.  Vegard reported
that sometimes UML is unable to spawn a xterm and he's facing the
following warning:

  WARNING: CPU: 0 PID: 908 at include/linux/thread_info.h:128 sigsuspend+0xab/0xc0()

It turned out that this warning makes absolutely no sense as the UML
xterm code calls sigsuspend() on the host side, at least it tries.  But
as the kernel itself offers a sigsuspend() symbol the linker choose this
one instead of the glibc wrapper.  Interestingly this code used to work
since ever but always blocked signals on the wrong side.  Some recent
kernel change made the WARN_ON() trigger and uncovered the bug.

It is a wonderful example of how much works by chance on computers. :-)

Fixes: 68f3f16d9ad0f1 ("new helper: sigsuspend()")
Signed-off-by: Richard Weinberger <richard@nod.at>
Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Tested-by: Vegard Nossum <vegard.nossum@oracle.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/signal.h b/include/linux/signal.h
index ab1e0392b5ac1ce89c80dc2bf0e4e4ccc7a736bd..92557bbce7e7b9a3d9c6c6ed4c4d4f54ff7ff9e5 100644 (file)
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -239,7 +239,6 @@ extern int sigprocmask(int, sigset_t *, sigset_t *);
 extern void set_current_blocked(sigset_t *);
 extern void __set_current_blocked(const sigset_t *);
 extern int show_unhandled_signals;
-extern int sigsuspend(sigset_t *);
 
 struct sigaction {
 #ifndef __ARCH_HAS_IRIX_SIGACTION

diff --git a/kernel/signal.c b/kernel/signal.c
index 0f6bbbe77b46c092d0de31e0c9eec8a0f17e6791..6c863ca42a769f7af7447c816cb7b5464e368748 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3552,7 +3552,7 @@ SYSCALL_DEFINE0(pause)
 
 #endif
 
-int sigsuspend(sigset_t *set)
+static int sigsuspend(sigset_t *set)
 {
        current->saved_sigmask = current->blocked;
        set_current_blocked(set);