Triton: Docker and the “best of all worlds”

Re:Triton: Docker and the “best of all worlds” by bch on Tuesday March 24, 2015 @07:35PM (#9260320)

Hi Bryan -- I'm also aware that epoll may have been a bad example on my part, because isn't it subject to some nasty fork/share bugs wrt handling the (well) handle, and what file it's actually associated with the handle -- so a parent can get notifications on a handle it doesn't have, or worse, notifications for a socket that it does have that is not really the same handle that's issuing the event.

In cases like that, did you end up trying to be bug-compatible, or make a design decision to clear up the trouble ?

[edit -- spell "Bryan" correctly]

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Re:Triton: Docker and the “best of all worlds” by bcantrill on Tuesday March 24, 2015 @07:41PM (#9260344)

Funny you should mention that one in particular -- from our (SmartOS's) epoll(5) man page:

       While  a  best effort has been made to mimic the Linux semantics, there
       are some semantics that are too  peculiar  or  ill-conceived  to  merit
       accommodation.   In  particular,  the  Linux  epoll facility will -- by
       design -- continue to  generate  events  for  closed  file  descriptors
       where/when  the underlying file description remains open.  For example,
       if one were to fork(2) and subsequently close an actively epoll'd  file
       descriptor  in  the  parent,  any  events generated in the child on the
       implicitly duplicated file descriptor will continue to be delivered  to
       the parent -- despite the fact that the parent itself no longer has any
       notion of the file description!  This epoll facility refuses  to  honor
       these  semantics;  closing  the  EPOLL_CTL_ADD'd  file  descriptor will
       always result in no further  events  being  generated  for  that  event
       description.

So while we do aspire to be bug-compatible, we're not about to compromise our principles over it. More details (or some of them, anyway) can be found in the talk on LX-branded zones that I gave at illumos Day at Surge 2014.[1][2]

[1] http://www.slideshare.net/bcantrill/illumos-lx

[2] https://www.youtube.com/watch?v=TrfD3pC0VSs

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