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+[[!meta copyright="Copyright © 2011, 2013, 2014 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]]."]]"""]]
+
+[[!meta title="clock_gettime"]]
+
+[[!tag open_issue_glibc open_issue_gnumach]]
+
+Missing `clock_gettime(CLOCK_MONOTONIC)` (e.g. for iceweasel)
+
+It could be a mere matter of extending the
+[[mapped-time_interface|microkernel/mach/gnumach/interface/device/time]]:
+add it to
+`mapped_time_value_t` in gnumach, handle it in `gnumach/kern/mach_clock.c`, and
+make `clock_gettime` use it.
+
+BTW, also make `gettimeofday()` use it, since it's way more efficient and some
+applications assume that it is.
+
+What about adding a nanosecond-precision clock, too?  --[[tschwinge]]
+
+
+# IRC, freenode, #hurd, 2011-08-26
+
+    < pinotree> youpi: thing is: apparently i found a simple way to have a
+      monotonic clock as mmap-able device inside gnumach
+    < pinotree> currently, in kern/mach_clock.c there's a variable 'time',
+      which gets increased on clock interrupt, and optionally modified by
+      host_set_time
+    < pinotree> ()
+    < pinotree> if i add a new variable next to it, only increasing it on
+      interrupt but not modifying it at all otherwise, would that give me a
+      monotonic clock?
+    < pinotree> at least on sme basic tests i did, it seems it could work that
+      way
+    < youpi> yes, it should work
+    < braunr> sure
+    < youpi> and that's the way I was considering implementing it
+
+
+# IRC, freenode, #hurd, 2011-09-06
+
+    <pinotree> yeah, i had a draft of improved idea for also handling
+      nanoseconds
+    <tschwinge> pinotree: Ah, nice, I thought about nanoseconds as well.
+    <tschwinge> pinotree, youpi: This memory page is all-zero by default,
+      right?
+    <tschwinge> Can't we then say that its last int is a version code, and if
+      it is 0 (as it is now), we only have the normal mapped time field, if it
+      is 1, we also have the monotonic cliock and ns precision on address 8 and
+      16 (or whatever)?
+    <tschwinge> In case that isn't your plan anyway.
+    <youpi> it's all-zero, yes
+    <tschwinge> Or, we say if a field is != 0 it is valid.
+    <youpi> making the last int a version code limits the size to one page
+    <youpi> I was thinking a field != 0  being valid is simpler
+    <youpi> but it's probably a problem too
+    <youpi> in that glibc usually caches whether interfaces are supported
+    <tschwinge> Wrap-around?
+    <youpi> for some clocks, it may be valid that the value is 0
+    <youpi> wrap-around is another issue too
+    <tschwinge> Well, then we can do the version-field thing, but put it right
+      after the current time field (address 8, I think)?
+    <youpi> yes
+    <youpi> it's a bit ugly, but it's hidden behind the structure
+    <tschwinge> It's not too bad, I think.
+    <youpi> yes
+    <tschwinge> And it will forever be a witness of the evolving of this
+      map_time interface.  :-)
+
+
+# IRC, freenode, #hurd, 2013-02-11
+
+In context of [[select]].
+
+    <pinotree> braunr: would you send for review (and inclusion) your
+      time_data_t addition?
+    <pinotree> this way we could add nanosecs-based utime rpc (and then their
+      implementation in libc)
+    <braunr> pinotree: it's part of the hurd branch
+    <braunr> do you want it sent separately ?
+    <pinotree> yeah
+    <braunr> ok
+    <braunr> let me get it right first :)
+    <pinotree> sure :)
+
+
+## IRC, freenode, #hurd, 2013-02-12
+
+    <braunr> pinotree:
+      http://git.savannah.gnu.org/cgit/hurd/hurd.git/commit/?h=rbraun/select_timeout_pthread_v2&id=6ec50e62d9792c803d00cbff1cab2c0b3675690a
+    <pinotree> uh nice
+    <pinotree> will need two small inline functions to convert time_data_t <->
+      timespec, but that's it
+    <braunr> hm right
+    <braunr> i could have thought about it
+    <braunr> but i'll leave it for another patch :p
+    <pinotree> oh sure, no hurry
+
+
+## IRC, freenode, #hurd, 2013-02-19
+
+    <youpi> braunr: about time_data_t, I get it's needed that it be an array
+    <youpi> so it can be passed by reference, not by value?
+    <braunr> by address, yes
+    <braunr> that's the difference between array and struct
+
+
+## IRC, freenode, #hurd, 2013-02-25
+
+    <youpi> braunr: why did you want to see time_data passed as pointer, not as
+      struct?
+    <braunr> to microoptimize
+    <braunr> the struct is 2 64-bit integers
+    <youpi> well, we already pass structs along in a few cases,
+      e.g. io_statbuf_t, rusage_t, etc.
+    <youpi> be it written t[0].sec or t->sec, it seems odd
+    <youpi> copying 2 64bit integers is not much compared to the potential for
+      bugs here
+    <braunr> bugs ?
+    <youpi> yes, as in trying to access t[1], passing a wrong pointer, etc.
+    <youpi> or the reader frowning on "why is this case different than the
+      others?"
+    <braunr> well, i'm already usually frowning when i see what mig does ..
+    <youpi> right
+    <youpi> on the plus side, it's only the client side, i.e. mostly glibc,
+      which sees the t[0]
+    <braunr> and the practice established by my patch is to convert to struct
+      timespec as soon as possible
+    <braunr> the direct use of this type is therefore limited
+    <youpi> could we define time_data_t as a struct time_data * instead of
+      struct time_data[1] ?
+    <youpi> (in the.h)
+    <youpi> that would make more sense to define a struct time_data, and pass a
+      pointer to it
+    <braunr> i'm not sure
+    <braunr> the mach server writing guide was very clear about array implying
+      a C array too
+    <braunr> and i remember having compilation problems before doing that
+    <braunr> but i don't remember their nature exactly 
+    <youpi> I'm not sure to understand what you said about converting to struct
+      timespec
+    <youpi> what makes it not possible now?
+    <youpi> and what is the relation with being an array or a pointer?
+    <braunr> concerning struct timespec, what i mean is that the functions
+      called by the mig stub code directly convert time_data_t to a struct
+      timespec (which is the real type used throughout the hurd code)
+    <braunr> about the rest, i'm not sure, i'd have to try again
+    <braunr> mig just assumes it's an array
+    <youpi> and why not just using struct timespec?
+    <youpi> (for the mig type too)
+    <braunr> my brain can't correctly compute variable sized types in mig
+      definition files
+    <braunr> i wanted something that would remain correct for the 64-bit port
+
+[[64-bit_port]], [[mig_portable_rpc_declarations]].
+
+    <youpi> ah, you mean because tv_nsec is a long, which will not be the same
+      type?
+    <braunr> and tv_sec being a time_t (thus a long too)
+    <youpi> but we have the same issue e.g. for the rusage structure, don't we?
+    <braunr> yes
+    <youpi> so we'll have to fix things for that too anyway
+    <braunr> sure
+    <youpi> making a special case will not necessarily help
+    <braunr> but it doesn't mean new interfaces have to be buggy too
+    <youpi> well, using the proper type in the server itself is nicer
+    <youpi> instead of having to convert
+    <braunr> yes
+    <braunr> i'm not exactly sure where to declare struct timespec then
+    <braunr> should it be declared in hurd_types.h, and simply reused by the
+      libc headers ?
+    <youpi> ? AIUI, it's the converse, hurd_types.h uses the struct timespec
+      from libc headers, and defines timespec_t
+    <braunr> ok
+    <youpi> timespec_t being the internal type whose definition gets done right
+      for mig to do the right thing
+    <braunr> yes
+    <braunr> i see
+    <braunr> so, you'd like a struct of integer_t instead of an array of
+      signed64
+    <youpi> for our current 32bit userland yes
+    <braunr> do you want to make the changes yourself or should i add a new
+      branch ?
+    <youpi> and we'll make that a 64bit struct when we have a64bit userland
+
+
+# IRC, freenode, #hurd, 2013-04-06
+
+    <tschwinge> pinotree: You had once been working on adding nsec-procision
+      timestamps to GNU Mach's maptime interface (or what the name is).  Is
+      that blocked on something or just waiting to be continued?
+    <pinotree> blocked on me needing to learn more the proper way to do
+      "atomic" update of the struct with time :)
+
+
+# IRC, freenode, #hurd, 2013-09-04
+
+    <teythoon> do we have CLOCK_MONOTONIC ?
+    <braunr> teythoon: i think we do but it's actually a simple offset from
+      CLOCK_REALTIME .. :)
+    <teythoon> ah never mind, I do hate this posix time interface anyways
+    <braunr> really ?
+    <braunr> i think librt is decent
+
+
+# Candidate for [[vDSO]] code?
+
+
+# IRC, freenode, #hurd, 2014-02-23
+
+    <desrt> GLib (gthread-posix.c): Unexpected error from C library during
+      'pthread_condattr_setclock': Invalid argument.  Aborting.
+    <desrt> uh oh...
+    <desrt> time to go digging in glibc i guess...
+    <braunr> what are you trying to run ?
+    <desrt> glib
+    <braunr> with what ?
+    <desrt> just running glib's test suite under jhbuild
+    <desrt> i maintain glib and i made some changes recently -- i wanted to
+      make sure they didn't break the hurd
+    <desrt> and it seems they have ;/
+    <braunr> well
+    <braunr> the hurd doesn't completely comply with posix 2008
+    <desrt> long story short: we've keyed our timed waits on condition
+      variables to the monotonic clock for a long time now, but we never tested
+      that it actually worked
+    <desrt> so i just added an assert -- and indeed it fails on hurd
+    <braunr> our glibc lies about supporting timers
+    <braunr> good thinking
+    <braunr> we don't support the monotonic clock
+    <desrt> clock_gettime(CLOCK_MONOTONIC) seems to work
+    <braunr> and you should know that, even if clock selection and timers are
+      available (which posix 2008 requires), it's still optional
+    <braunr> no, glibc lies
+    <desrt> !!
+    <braunr> our "support" is a mere hack shifting CLOCK_REALTIME
+    <desrt> it should at least lie consistently :)
+    <braunr> we need to implement CLOCK_MONOTONIC properly
+    <desrt> ya... that would be very nice indeed
+    <braunr> not that hard either
+    <desrt> i agree!
+    <braunr> we just have to do it right
+    <desrt> fwiw, i plan to keep this assert in glib
+    <braunr> yes, it's good
+    <desrt> is there anywhere i can file a bug to give you guys some advance
+      warning?
+    <braunr> i don't think it's needed
+    <braunr> we know the problem
+    <desrt> k -- consider yourself warned, then :)
+    <braunr> and it's been a bigger concern recently
+    <desrt> awesome.  glad i don't have to do anything :)
+    <braunr> if it's not already done, i suggest you check for the
+      CLOCK_MONOTONIC option
+    <desrt> fwiw, i'm trying to get a regular debian/gnu/hurd build of
+      glib/gtk/etc setup
+    <braunr> regular ?
+    <desrt> ya... out of git master on a daily basis
+    <braunr> from sources ?
+    <braunr> oh nice
+    <desrt> we recently set this up for freebsd as well
+    <braunr> few maintainers take the pain :)
+    <desrt> our non-linux 'problem discovery' is a bit crap before now :/
+    <braunr> i guess that's pretty normal
+    <braunr> i don't consider it the responsibility of the maintainers to test
+      every possible platform
+    <desrt> glib is a bit unique -- portability is our business
+    <braunr> taking our patches into consideration is what we ask most
+    <braunr> right
+    <desrt> and the "please take the patches" thing is something we want to
+      stop doing
+    <braunr> why ?
+    <desrt> mostly because we often look at a patch that someone sent a few
+      years ago and say "do we even still need this?"
+    <desrt> and have no way to know
+    <braunr> uh
+    <desrt> you would not believe how many patches like this we've
+      accumulated...
+    <braunr> but if we send it now ? :)
+    <desrt> braunr: new policy is roughly this:
+      https://wiki.gnome.org/Projects/GLib/SupportedPlatforms
+    <desrt> ie: fixes for issues that are general portability improvements and
+      POSIX compliance are welcome...
+    <desrt> patches that introduce platform-specific #ifdef sections are
+      rejected unless we have a regular builder to test that code
+    <braunr> i see
+    <braunr> again, regarding portability, don't consider CLOCK_MONOTONIC to be
+      readily available, check for it
+    <braunr> an #error would be enough but it has to be checked
+    <desrt> it basically comes down to: we don't want to have code in our
+      version control that we have no possible way of testing
+    <braunr> yes
+    <desrt> braunr: we do check for it
+    <braunr> ok
+    <desrt> we assert() if clock_gettime(CLOCK_MONOTONIC) fails
+    <braunr> no i mean
+    <desrt> as POSIX said it should if CLOCK_MONOTONIC is not supported
+    <desrt> if you lie to us.... well, not much we can do
+    <braunr> POSIX_MONOTONIC_CLOCK
+    <braunr> _POSIX_MONOTONIC_CLOCK
+    <desrt> this is actually defined to 0 on most platforms...
+    <desrt> which does not mean that it's unsupported -- it means that the
+      runtime must be ready to deal with it not actually existing at runtime
+    <braunr> really ?
+    <desrt> yes
+    <desrt> we used to rely on this and got a bug that we were doing it wrong
+      :)
+    <desrt> and indeed, even on linux, both with glibc and uclibc:
+    <desrt> /usr/include/bits/posix_opt.h:#define _POSIX_MONOTONIC_CLOCK
+      0
+    <desrt> /usr/include/uClibc/bits/posix_opt.h:#define _POSIX_MONOTONIC_CLOCK
+      0
+    <braunr> ok it's described in 2.1.6 Options
+    <braunr> so your check is appropriate
+    <desrt> so does clock_gettime(MONOTONIC) on debian/hurd get me realtime?
+    <braunr> either that, or a value shifted from it
+    <desrt> if so, i'll just hack out the condattr_setclock() check and proceed
+      trying to build past glib...
+    * desrt checks
+    <desrt> as it is, even the build of glib fails since we use some tools
+      linked against ourselves during the build process...
+    <desrt> 1393124084790000 1393124084790000
+    <desrt> those look the same....
+    <braunr> heh
+    <desrt> i also notice that your clocks are not very high precision :)
+    <braunr> that's right
+    <desrt> HZ = 100, i guess
+    <braunr> yes
+    <desrt> fair enough
+    <desrt> our mainloop doesn't support better-than-millisecond accuracy yet
+      anyway :)
+    <desrt> (although it will soon...)
+    <braunr> nice
+
+
+## IRC, freenode, #hurd, 2014-03-05
+
+    <desrt> braunr: bit of a warning: i released the glib that depends on
+      working pthread_condattr_setclock(..._MONOTONIC) and pochu said that it
+      will be landing in debian within the next days
+    <braunr> desrt: ok