From 2603401fa1f899a8ff60ec6a134d5bd511073a9d Mon Sep 17 00:00:00 2001 From: Thomas Schwinge Date: Tue, 7 Aug 2012 23:25:26 +0200 Subject: IRC. --- open_issues/synchronous_ipc.mdwn | 64 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 64 insertions(+) create mode 100644 open_issues/synchronous_ipc.mdwn (limited to 'open_issues/synchronous_ipc.mdwn') diff --git a/open_issues/synchronous_ipc.mdwn b/open_issues/synchronous_ipc.mdwn new file mode 100644 index 00000000..57bcdda7 --- /dev/null +++ b/open_issues/synchronous_ipc.mdwn @@ -0,0 +1,64 @@ +[[!meta copyright="Copyright © 2012 Free Software Foundation, Inc."]] + +[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable +id="license" text="Permission is granted to copy, distribute and/or modify this +document under the terms of the GNU Free Documentation License, Version 1.2 or +any later version published by the Free Software Foundation; with no Invariant +Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license +is included in the section entitled [[GNU Free Documentation +License|/fdl]]."]]"""]] + +[[!tag open_issue_hurd]] + + +# IRC, freenode, #hurd, 2012-07-20 + +From [[Genode RPC|microkernel/genode/rpc]]. + + assuming synchronous ipc is the way to go (it seems so), there is + still the need for some async ipc (e.g signalling untrusted recipients + without risking blocking on them) + 1/ do you agree on that and 2/ how would this low-overhead async + ipc be done ? (and 3/ are there relevant examples ? + if you think about this stuff too much you will end up like marcus + and neal ;-) + antrik: likely :) + the truth is that there are various possible designs all with + their own tradeoffs, and nobody can really tell which one is better + the only sensible one i found is qnx :/ + but it's still messy + they have what they call pulses, with a strictly defined format + so it's actually fine because it guarantees low overhead, and can + easily be queued + but i'm not sure about the format + I must say that Neal's half-sync approach in Viengoos still sounds + most promising to me. it's actually modelled after the needs of a + Hurd-like system; and he thought about it a lot... + damn i forgot to reread that + stupid me + note that you can't come up with a design that allows both a) + delivering reliably and b) never blocking the sender -- unless you cache + in the kernel, which we don't want + but I don't think it's really necessary to fulfill both of these + requirements + it's up to the receiver to make sure it gets important signals + right + caching in the kernel is ok as long as the limit allows the + receiver to handle its signals + in the Viengoos approach, the receiver can allocate a number of + receive buffers; so it's even possible to do some queuing if desired + ah great, limits in the form of resources lent by the receiver + one thing i really don't like in mach is the behaviour on full + message queues + blocking :/ + i bet the libpager deadlock is due to that + +[[libpager_deadlock]]. + + it simply means async ipc doesn't prevent at all from deadlocks + the sender can set a timeout. blocking only happens when setting + it to infinite... + which is commonly the case + well, if you see places where blocking is done but failing would + be more appropriate, try changing them I'd say... + it's not that easy :/ -- cgit v1.2.3