PIDTYPE_TGID removal of fork restarts

This took longer than I thought to address all of the issues and double check I am not missing something. I have split of a few of the patches
so now the patch series appears longer. It now covers less ground.

I realized while reviewing the group signals that for none of them is siginfo important. Which means by slightly lowering our quality of implementation in delivering those signals to a brand new process (by not queueing siginfo) I can collect them all in a sigset and the code is no more difficult than a sequence counter. Which means it is straight forward to completely eliminate restarts from fork.

The implemenatation of PIDTYPE_TGID remains the same. How it gets used has changed to guarantee that looking up a thread group by the pid of one of it's threads and sending it a signal continues to work exactly the same as before.

Please take a look and verify that I have caught everything. I think I have but if not please let me know.

Thank you in advance,
Eric

Eric W. Biederman (20):
pids: Initialize leader_pid in init_task
pids: Move task_pid_type into sched/signal.h
pids: Compute task_tgid using signal->leader_pid
kvm: Don't open code task_pid in kvm_vcpu_ioctl
pids: Move the pgrp and session pid pointers from task_struct to signal_struct
pid: Implement PIDTYPE_TGID
signal: Use PIDTYPE_TGID to clearly store where file signals will be sent
posix-timers: Noralize good_sigevent
signal: Pass pid and pid type into send_sigqueue
signal: Pass pid type into group_send_sig_info
signal: Pass pid type into send_sigio_to_task & send_sigurg_to_task
signal: Pass pid type into do_send_sig_info
signal: Push pid type down into send_signal
signal: Push pid type down into __send_signal
signal: Push pid type down into complete_signal.
fork: Move and describe why the code examines PIDNS_ADDING
fork: Unconditionally exit if a fatal signal is pending
signal: Add calculate_sigpending()
fork: Have new threads join on-going signal group stops
signal: Don't restart fork when signals come in.

 arch/ia64/kernel/asm-offsets.c       |  4 +-
 arch/ia64/kernel/fsys.S              | 12 ++---
 arch/s390/kernel/perf_cpum_sf.c      |  2 +-
 drivers/net/tun.c                    |  2 +-
 drivers/platform/x86/thinkpad_acpi.c |  1 +
 drivers/tty/sysrq.c                  |  2 +-
 drivers/tty/tty_io.c                 |  2 +-
 fs/autofs/autofs_i.h                 |  1 +
 fs/exec.c                            |  1 +
 fs/fcntl.c                           | 72 +++++++++++++--------------
 fs/fuse/file.c                       |  1 +
 fs/locks.c                           |  2 +-
 fs/notify/dnotify/dnotify.c          |  3 +-
 fs/notify/fanotify/fanotify.c        |  1 +
 include/linux/init_task.h            |  9 ----
 include/linux/pid.h                  | 11 +----
 include/linux/sched.h                | 31 +++---------
 include/linux/sched/signal.h         | 49 +++++++++++++++++--
 include/linux/signal.h               |  6 ++-
 include/net/scm.h                    |  1 +
 init/init_task.c                     | 12 +++--
 kernel/events/core.c                 |  2 +-
 kernel/exit.c                        | 12 ++---
 kernel/fork.c                        | 70 +++++++++++++++++++--------
 kernel/pid.c                         | 42 ++++++++--------
 kernel/signal.c                      | 94 ++++++++++++++++++++++++++----------
 kernel/time/itimer.c                 |  5 +-
 kernel/time/posix-cpu-timers.c       |  2 +-
 kernel/time/posix-timers.c           | 21 ++++----
 mm/oom_kill.c                        |  4 +-
 virt/kvm/kvm_main.c                  |  2 +-
 31 files changed, 282 insertions(+), 197 deletions(-)