linux-kernel - [PATCH 00/20] PIDTYPE_TGID removal of fork restarts

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Date:   Mon, 23 Jul 2018 22:22:58 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Oleg Nesterov <oleg@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <linux-kernel@...r.kernel.org>, Wen Yang <wen.yang99@....com.cn>,
        majiang <ma.jiang@....com.cn>
Subject: [PATCH 00/20] 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(-)