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From:   ebiederm@xmission.com (Eric W. Biederman)
To:     Oleg Nesterov <oleg@redhat.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        <linux-kernel@vger.kernel.org>, Wen Yang <wen.yang99@zte.com.cn>,
        majiang <ma.jiang@zte.com.cn>,
        Linus Torvalds <torvalds@linux-foundation.org>
References: <bug-200447-5873-b2kAsSyE1X@https.bugzilla.kernel.org/>
        <CA+55aFyOaEGc_wjRuAxYZH7D4zi4xUQTqUwMmUzxFJQ__2pXuQ@mail.gmail.com>
        <87h8l9p7bg.fsf@xmission.com> <20180709104158.GA23796@redhat.com>
        <87sh4so5jv.fsf@xmission.com> <20180709145726.GA26149@redhat.com>
        <877em4nxo0.fsf@xmission.com>
        <CA+55aFwq90_KeRUesktap7L_4Hp3gatKZ28RYw1jXBYeOqUoeA@mail.gmail.com>
        <87lgakm4ol.fsf@xmission.com>
        <CA+55aFz1XFvOgJySKVNQD9VS4hys0J7rozxqd3s5ND0z80tfVw@mail.gmail.com>
        <20180710134639.GA2453@redhat.com>
        <CA+55aFxcjSYAj-CZFEuDwiwZyMg+prV_jeP_Vuh06RJA0BboSw@mail.gmail.com>
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Date:   Thu, 09 Aug 2018 01:53:02 -0500
In-Reply-To: <87efft5ncd.fsf_-_@xmission.com> (Eric W. Biederman's message of
        "Mon, 23 Jul 2018 22:22:58 -0500")
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Subject: [PATCH v5 0/6] Not restarting for due to signals.
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This builds on patches 1-15 of my previous patch posting.  As those are
non-controversial I am not posting them again.

I took longer than I had hoped to get this set together because a kernel
testing robot noticed some random corruption with the way I had been
adding to the list.  I finally tracked it down to failing to remove the
sigset from the list during fork_idle.  So I have made that logic
simpler and use hlist_del_init which will only remove an item from a
list if it was placed on the list in the first place.

I took Oleg's suggesting and moved calculate_sigpending into
schedule_tail where recalc_sigpending an be used directly.  Then in
calculate_sigpending I just unconditionally set TIF_SIGPENDING and allow
recalc_sigpending to clear TIF_SIGPENDING if we don't need it.

I also now handle the stop/continue signal magic where we only let one
of stop signals and SIGCONT be pending at a time.  Looking at it from
first principles dropping one of SIGTSTP SIGTTIN SIGTTOU or SIGCONT
before calling it's handler feels wrong.  I checked and it is our
historical behavior, so I won't even thinking of introducing different
behavior at this point.

Eric W. Biederman (6):
      fork: Move and describe why the code examines PIDNS_ADDING
      fork: Unconditionally exit if a fatal signal is pending
      signal: Add calculate_sigpending()
      fork: Skip setting TIF_SIGPENDING in ptrace_init_task
      fork: Have new threads join on-going signal group stops
      signal: Don't restart fork when signals come in.

 include/linux/ptrace.h       |  2 --
 include/linux/sched/signal.h | 11 ++++++++++
 init/init_task.c             |  1 +
 kernel/fork.c                | 49 ++++++++++++++++++++++++++++++--------------
 kernel/sched/core.c          |  2 ++
 kernel/signal.c              | 43 ++++++++++++++++++++++++++++++++++++++
 6 files changed, 91 insertions(+), 17 deletions(-)

Eric