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    Subject[PATCH 4.3 032/200] kernel/signal.c: unexport sigsuspend()
    Date
    4.3-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Richard Weinberger <richard@nod.at>

    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>

    ---
    include/linux/signal.h | 1 -
    kernel/signal.c | 2 +-
    2 files changed, 1 insertion(+), 2 deletions(-)

    --- a/include/linux/signal.h
    +++ b/include/linux/signal.h
    @@ -239,7 +239,6 @@ extern int sigprocmask(int, 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
    --- 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);

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