Re: [RFC][PATCH 0/6][v3] Container-init signal semantics

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From: Sukadev Bhattiprolu
Date: Monday, December 22, 2008 - 7:12 pm

Eric W. Biederman [ebiederm@xmission.com] wrote:
| I haven't dug in too deep but right now my concern are user space semantics,
| I don't want to wind up with something ugly there because we can not change
| it later.

The one restriction we are imposing is that SIGINT, SIGTERM etc will not
currently kill containter-inits. Only SIGKILL will.  But that is good point.
Maybe we should document that as a limitation we may remove in the future ? 
i.e. Its not a feature that container-inits should rely on.  Like sysV init,
container-init should still SIG_IGN all unhandled signals. If they don't,
they may break in the future.

| 
| So if we can write a description of what happens to signals to cinit
| that is right 100% of the time.  Something we can write a test case
| for that tests all of the corner cases and it always get the same
| results. I am happy.

Yes, I believe we can say that SIGKILL/SIGSTOP from parent are always
delivered and no fatal signal from same ns is.

| 
| I don't mind dropping signals early as an optimization, but if it
| is just an optimization we can't count on it in cinit.

Yes, you have a point. It started out as an optimization, but unwanted
signals are either ignored or dropped _always_ (or we have a bug).

| 
| So I would rather deliver less and make user space deal with it,
| then deliver more cause problems for user space.

The user-semantics appear to be clean now.
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Messages in current thread:
[RFC][PATCH 0/6][v3] Container-init signal semantics, Sukadev Bhattiprolu, (Sat Dec 20, 5:51 pm)
[RFC][PATCH 1/6][v3] Remove 'handler' parameter to traceho ..., Sukadev Bhattiprolu, (Sat Dec 20, 5:52 pm)
[RFC][PATCH 2/6][v3] Protect init from unwanted signals more, Sukadev Bhattiprolu, (Sat Dec 20, 5:53 pm)
[RFC][PATCH 3/6][v3] Define/set SIGNAL_UNKILLABLE_FROM_NS, Sukadev Bhattiprolu, (Sat Dec 20, 5:53 pm)
[RFC][PATCH 4/6][v3] Define siginfo_from_ancestor_ns(), Sukadev Bhattiprolu, (Sat Dec 20, 5:54 pm)
[RFC][PATCH 5/6][v3] Protect cinit from unblocked SIG_DFL ..., Sukadev Bhattiprolu, (Sat Dec 20, 5:54 pm)
[RFC][PATCH 6/6][v3] Protect cinit from blocked fatal signals, Sukadev Bhattiprolu, (Sat Dec 20, 5:55 pm)
Re: [RFC][PATCH 0/6][v3] Container-init signal semantics, Eric W. Biederman, (Mon Dec 22, 3:55 am)
Re: [RFC][PATCH 0/6][v3] Container-init signal semantics, Sukadev Bhattiprolu, (Mon Dec 22, 12:47 pm)
Re: [RFC][PATCH 6/6][v3] Protect cinit from blocked fatal ..., Sukadev Bhattiprolu, (Mon Dec 22, 4:38 pm)
Re: [RFC][PATCH 4/6][v3] Define siginfo_from_ancestor_ns(), Sukadev Bhattiprolu, (Mon Dec 22, 4:45 pm)
Re: [RFC][PATCH 4/6][v3] Define siginfo_from_ancestor_ns(), Sukadev Bhattiprolu, (Mon Dec 22, 4:58 pm)
Re: [RFC][PATCH 0/6][v3] Container-init signal semantics, Eric W. Biederman, (Mon Dec 22, 5:27 pm)
Re: [RFC][PATCH 4/6][v3] Define siginfo_from_ancestor_ns(), Eric W. Biederman, (Mon Dec 22, 5:32 pm)
Re: [RFC][PATCH 0/6][v3] Container-init signal semantics, Sukadev Bhattiprolu, (Mon Dec 22, 7:12 pm)
Re: [RFC][PATCH 4/6][v3] Define siginfo_from_ancestor_ns(), Sukadev Bhattiprolu, (Mon Dec 22, 9:47 pm)
Re: [RFC][PATCH 0/6][v3] Container-init signal semantics, Serge E. Hallyn, (Tue Dec 23, 9:51 am)