diff options
Diffstat (limited to 'glibc')
| -rw-r--r-- | glibc/debugging.mdwn | 11 | ||||
| -rw-r--r-- | glibc/debugging/ld_so_console.mdwn | 20 | ||||
| -rw-r--r-- | glibc/debugging/ld_so_console/dl-sysdep.c.patch | 63 | ||||
| -rw-r--r-- | glibc/discussion.mdwn | 25 | ||||
| -rw-r--r-- | glibc/environment_variable.mdwn | 15 | ||||
| -rw-r--r-- | glibc/fallocate.mdwn | 17 | ||||
| -rw-r--r-- | glibc/file_descriptor.mdwn | 13 | ||||
| -rw-r--r-- | glibc/fork.mdwn | 69 | ||||
| -rw-r--r-- | glibc/ioctl.mdwn | 52 | ||||
| -rw-r--r-- | glibc/mmap.mdwn | 98 | ||||
| -rw-r--r-- | glibc/poll.mdwn | 15 | ||||
| -rw-r--r-- | glibc/process.mdwn | 26 | ||||
| -rw-r--r-- | glibc/signal.mdwn | 35 | ||||
| -rw-r--r-- | glibc/signal/signal_thread.mdwn | 100 | ||||
| -rw-r--r-- | glibc/startup.mdwn | 20 |
15 files changed, 0 insertions, 579 deletions
diff --git a/glibc/debugging.mdwn b/glibc/debugging.mdwn deleted file mode 100644 index 6b035c12..00000000 --- a/glibc/debugging.mdwn +++ /dev/null @@ -1,11 +0,0 @@ -[[!meta copyright="Copyright © 2011 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]]."]]"""]] - - * [[ld_so_console]] diff --git a/glibc/debugging/ld_so_console.mdwn b/glibc/debugging/ld_so_console.mdwn deleted file mode 100644 index b3d1762f..00000000 --- a/glibc/debugging/ld_so_console.mdwn +++ /dev/null @@ -1,20 +0,0 @@ -[[!meta copyright="Copyright © 2011 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]]."]]"""]] - -If you need to debug something in the early `ld.so` startup, and can't refrain -from good old `printf` debugging, there is a caveat: the available API in -`ld.so` is rather limited. See the few functions is `dl-sysdep.c`. For -example, there's a private `__libc_write`, which you should be able to use for -writing to FD stderr -- but, at early `ld.so` startup, this isn't usable as -`_hurd_init_dtable` is still all zeros, etc. To get you started, here is a -simple [[dl-sysdep.c.patch]] to get access to the Mach console. - -Can this be integrated with the other debugging printf functions from -`elf/dl-misc.c` (`_dl_debug_vdprintf`) ([[!taglink open_issue_glibc]])? diff --git a/glibc/debugging/ld_so_console/dl-sysdep.c.patch b/glibc/debugging/ld_so_console/dl-sysdep.c.patch deleted file mode 100644 index eec8d7c6..00000000 --- a/glibc/debugging/ld_so_console/dl-sysdep.c.patch +++ /dev/null @@ -1,63 +0,0 @@ -diff --git a/sysdeps/mach/hurd/dl-sysdep.c b/sysdeps/mach/hurd/dl-sysdep.c -index ff37add..7e6d352 100644 ---- a/sysdeps/mach/hurd/dl-sysdep.c -+++ b/sysdeps/mach/hurd/dl-sysdep.c -@@ -44,6 +44,8 @@ - #include <dl-machine.h> - #include <dl-procinfo.h> - -+#include <device/device.h> -+ - extern void __mach_init (void); - - extern int _dl_argc; -@@ -116,6 +118,29 @@ static void fmh(void) { - /* XXX loser kludge for vm_map kernel bug */ - #endif - -+/* Return a port to the Mach console. */ -+static mach_port_t -+get_console (void) -+{ -+ mach_port_t device_master, console; -+ /* We cannot use __get_privileged_ports (from hurd/privports.c), as this -+ drags in too much other libc stuff. */ -+#if 0 -+ error_t err = __get_privileged_ports (0, &device_master); -+ -+ if (err) -+ return MACH_PORT_NULL; -+#else -+ error_t err = 0; -+ device_master = 2; -+#endif -+ -+ err = __device_open (device_master, D_WRITE | D_READ, "console", &console); -+ if (err) -+ return MACH_PORT_NULL; -+ -+ return console; -+} - - ElfW(Addr) - _dl_sysdep_start (void **start_argptr, -@@ -256,6 +279,20 @@ unfmh(); /* XXX */ - /* Set up so we can do RPCs. */ - __mach_init (); - -+ /* Open the Mach console so that any message can actually be seen. This is -+ particularly useful at boot time, when started by the bootstrap file -+ system. */ -+ mach_port_t console = get_console (); -+ if (console != MACH_PORT_NULL) -+ { -+ /* stdout = mach_open_devstream (console, "w"); */ -+ /* stderr = stdout; */ -+ /* if (stdout != NULL) */ -+ /* printf ("Hello, world!\n"); */ -+ int written; -+ __device_write_inband (console, 0, 0, "hello, world!\n", 14, &written); -+ } -+ - /* Initialize frequently used global variable. */ - GLRO(dl_pagesize) = __getpagesize ();
\ No newline at end of file diff --git a/glibc/discussion.mdwn b/glibc/discussion.mdwn deleted file mode 100644 index fac300ea..00000000 --- a/glibc/discussion.mdwn +++ /dev/null @@ -1,25 +0,0 @@ -[[!meta copyright="Copyright © 2011 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]]."]]"""]] - - -# TLS - - -## IRC, freenode, #hurd, 2011-06-11 - -[[!tag open_issue_documentation open_issue_glibc]] - - <civodul> youpi: local-tls-support.diff removes libc-tsd.h; what's the - rationale? - <youpi> it's completely replaced by __thread variables - <civodul> ok, but apparently there are still libc headers that #include it - <civodul> like malloc-machine.h - <youpi> they'll include bits/libc-tsd.h instead - <civodul> oh, ok diff --git a/glibc/environment_variable.mdwn b/glibc/environment_variable.mdwn deleted file mode 100644 index 76c1371e..00000000 --- a/glibc/environment_variable.mdwn +++ /dev/null @@ -1,15 +0,0 @@ -[[!meta copyright="Copyright © 2010 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]]."]]"""]] - - -# External - - * [*putenv() and setenv()*](http://www.greenend.org.uk/rjk/2008/putenv.html) - by Richard Kettlewell. diff --git a/glibc/fallocate.mdwn b/glibc/fallocate.mdwn deleted file mode 100644 index 3aecf16b..00000000 --- a/glibc/fallocate.mdwn +++ /dev/null @@ -1,17 +0,0 @@ -[[!meta copyright="Copyright © 2010 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]]."]]"""]] - -Not yet implemented for the GNU Hurd in [[glibc]]. - - -# External - - * [*Punching holes in files*](http://lwn.net/Articles/415889/), Jonathan - Corbet, 2010-11-17. diff --git a/glibc/file_descriptor.mdwn b/glibc/file_descriptor.mdwn deleted file mode 100644 index 2c56d070..00000000 --- a/glibc/file_descriptor.mdwn +++ /dev/null @@ -1,13 +0,0 @@ -[[!meta copyright="Copyright © 2010 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]]."]]"""]] - -A [[UNIX file descriptor|unix/file_descriptor]] is implemented in [[glibc]] by -using operations on objects referred to by [[Mach -ports|microkernel/mach/port]]). diff --git a/glibc/fork.mdwn b/glibc/fork.mdwn deleted file mode 100644 index 12ca2d19..00000000 --- a/glibc/fork.mdwn +++ /dev/null @@ -1,69 +0,0 @@ -[[!meta copyright="Copyright © 2010, 2011 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]]."]]"""]] - -On [[Unix]] systems, `fork` is a rather simple [[system call]]. - -Our implementation in [[glibc]] is and needs to be rather bulky. - -For example, it has to duplicate all port rights for the new [[Mach -task|microkernel/mach/task]]. The address space can simply be duplicated by -standard means of the [[microkernel/Mach]], but as [[unix/file_descriptor]]s -(for example) are a concept that is implemented inside [[glibc]] (based on -[[Mach port|microkernel/mach/port]]s), these have to be duplicated from -userspace, which requires a small number of [[RPC]]s for each of them, and in -the sum, [[this affects performance|open_issues/performance/fork]] when new -processes are continuously being spawned from the shell, for example. - -Often, a `fork` call will eventually be followed by an `exec`, which [[may in -turn close|open_issues/secure_file_descriptor_handling]] (most of) the -duplicated port rights. Unfortunately, this cannot be known at the time the -`fork` executing, so in order to optimize this, the code calling `fork` has to -be modified instead, and the `fork`, `exec` combo be replaced by a -`posix_spawn` call, for example, to avoid this work of duplicating each port -right, then closing each again. - -As far as we know, Cygwin has the same problem of `fork` being a nontrivial -operation. Perhaps we can learn from what they're been doing? Also, perhaps -they have patches for software packages, to avoid using `fork` followed by -`exec`, for example. - - -# TODO - - * [[fork: mach_port_mod_refs: - EKERN_UREFS_OWERFLOW|open_issues/fork_mach_port_mod_refs_ekern_urefs_owerflow]] - ([[!taglink open_issue_glibc]]). - - * Include de-duplicate information from elsewhere: [[hurd-paper]], - [[hurd-talk]], [[hurd/ng/trivialconfinementvsconstructorvsfork]], - [[open_issues/resource_management_problems/zalloc_panics]] ([[!taglink - open_issue_glibc open_issue_documentation]]). - - * We no longer support `MACH_IPC_COMPAT`, thus we can get rid of the `err = - __mach_port_allocate_name ([...]); if (err == KERN_NAME_EXISTS)` code - ([[!taglink open_issue_glibc]]). - - * Can we/why can't we use the concept of *inherited ports - array*s/`mach_ports_register` ([[!taglink open_issue_glibc]])? - - * GNUnet `vfork` signal race issue: [[!message-id - "87r50ww6m4.fsf@kepler.schwinge.homeip.net"]]. - - -## Related - - * [[open_issues/secure_file_descriptor_handling]]. - - -# External - - * {{$unix#djb_self-pipe}}. - - * {{$unix#rjk_fork}}. diff --git a/glibc/ioctl.mdwn b/glibc/ioctl.mdwn deleted file mode 100644 index e1a86f32..00000000 --- a/glibc/ioctl.mdwn +++ /dev/null @@ -1,52 +0,0 @@ -[[!meta copyright="Copyright © 2011 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_documentation]] - -IRC, freenode, #hurd, 2011-10-31: - - <pinotree> is there some example of translator replying to custom ioctl's? - <pinotree> let's say you define some ioctl (those which can be represented) - using the _IOW etc macros; how would a translator (or something else) - "register" and reply to them? - <youpi> it's not an easy thing - <youpi> see hurd/hurd/tioctl.defs for instance - <youpi> that's where the 't' ioctls end up - <youpi> ('t' being the group in the _IOW macro) - <braunr> it's not that hard either - <pinotree> youpi: so you "roll" the ioctl to an ipc call with proper - parameters? - <braunr> yes - <pinotree> ah ok, i thought there was some way to hook new ioctl's, and - have libc send the whole stuff at once - <braunr> and the proper number (with a clear name) - <braunr> hm - <braunr> for many ioctls, you don't have to change libc - <youpi> yes, there's a script which produces the .defs from _IOW calls, - iirc - <youpi> or something like this - <youpi> there's also a hook thing in glibc, but for "sane" ioctls, that's - not needed - <youpi> (_hurd_lookup_ioctl_handler called by ioctl()) - <youpi> yes, see the rules in hurd/hurd/Makefile - <youpi> "The following rules assist in creating an `Xioctl.defs' file to - define RPCs that are sent primarily by ioctl commands." - <antrik> well, you can have perfectly sane ioctl()s that still can't be - expressed within the constraints of the IO* macros... but admittedly - that's rather uncommon - <antrik> (unless you consider passing of structs generally insane...) - <youpi> I didn't want to spend time on finding an appropriate adjective - instaed of "sane" - <youpi> while I knew he would understand what I meant (and you did) - <youpi> (though maybe not actually) - <youpi> by "sane", I mean, which use _IOW properly - <youpi> i.e. with a group, proper numbers, etc. - <youpi> (the imposed contraints on the parameters is obviously a flaw in - the hurdish ioctl design, and not insanity from structures) diff --git a/glibc/mmap.mdwn b/glibc/mmap.mdwn deleted file mode 100644 index 09b0b65d..00000000 --- a/glibc/mmap.mdwn +++ /dev/null @@ -1,98 +0,0 @@ -[[!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]]."]]"""]] - -There are two implementations of `mmap` for GNU Hurd: -`sysdeps/mach/hurd/mmap.c` (main implementation) and -`sysdeps/mach/hurd/dl-sysdep.c` (*Minimal mmap implementation sufficient for -initial loading of shared libraries.*). - - * `MAP_COPY` - - What exactly is that? `elf/dl-load.c` has some explanation. - <http://lkml.indiana.edu/hypermail/linux/kernel/0110.1/1506.html> - - It is only handled in `dl-sysdep.c`, when `flags & (MAP_COPY|MAP_PRIVATE)` - is used for `vm_map`'s `copy` parameter, and `mmap.c` uses `! (flags & - MAP_SHARED)` instead, which seems inconsistent? - - -# `io_map` Failure - -This is the [[libnetfs: `io_map`|open_issues/libnetfs_io_map]] issue. - -[[!tag open_issue_glibc]] - -Review of `mmap` usage in generic bits of glibc, based on -a1bcbd4035ac2483dc10da150d4db46f3e1744f8 (2012-03-11), listing these cases -where failure (due to `io_map` failing; that is, invocations where a `fd` is -passed) is not properly handled. - -`catgets/open_catalog.c`, `iconv/gconv_cache.c`, `intl/loadmsgcat.c`, -`locale/loadlocale.c` have fallback code for the `MAP_FAILED` case. - -[[tschwinge]]'s current plan is to make the following cases do the same (if -that is possible); probably by introducing a generic `mmap_or_read` function, -that first tries `mmap` (and that will succeed on Linux-based systems and also -on Hurd-based, if it's backed by [[hurd/libdiskfs]]), and if that fails tries -`mmap` on anonymous memory and then fills it by `read`ing the required data. -This is also what the [[hurd/exec]] server is doing (and is the reason that the -`./true` invocation on [[libnetfs: `io_map`|open_issues/libnetfs_io_map]] -works, to my understanding): see `exec.c:prepare`, if `io_map` fails, -`e->filemap == MACH_PORT_NULL`; then `exec.c:map` (as invoked from -`exec.c:load_section`, `exec.c:check_elf`, `exec.c:do_exec`, or -`hashexec.c:check_hashbang`) will use `io_read` instead. - -Doing so potentially means reading in a lot of unused data -- but we probably -can't do any better? - -In parallel (or even alternatively?), it should be researched how Linux (or any -other kernel) implements `mmap` on NFS and similar file systems, and then -implement the same in [[hurd/libnetfs]] and/or [[hurd/translator/nfs]], etc. - -Here, also probably the whole mapping region [has to be -read](http://lists.gnu.org/archive/html/bug-hurd/2001-10/msg00306.html) at -`mmap` time. - -List of files without fallback code for the *`MAP_FAILED` due to `io_map` -failed* case: - - * `elf/cache.c` - - * `elf/dl-load.c` - - * `elf/dl-misc.c` - - * `elf/dl-profile.c` - - * `elf/readlib.c` - - * `elf/sprof.c` - - * `locale/loadarchive.c` - - * `locale/programs/locale.c` - - * `locale/programs/locarchive.c` - - * `nscd/connections.c` - - * `nscd/nscd_helper.c` - - * `nss/makedb.c` - - * `nss/nss_db/db-open.c` - - * Omitted: - - * `nptl/` - - * `sysdeps/unix/sparc/` - - * `sysdepts/unix/sysv/linux/` diff --git a/glibc/poll.mdwn b/glibc/poll.mdwn deleted file mode 100644 index d96f27a5..00000000 --- a/glibc/poll.mdwn +++ /dev/null @@ -1,15 +0,0 @@ -[[!meta copyright="Copyright © 2010 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]]."]]"""]] - - -# External - - * [*poll() and EOF*](http://www.greenend.org.uk/rjk/2001/06/poll.html) by - Richard Kettlewell. diff --git a/glibc/process.mdwn b/glibc/process.mdwn deleted file mode 100644 index 9b2ec251..00000000 --- a/glibc/process.mdwn +++ /dev/null @@ -1,26 +0,0 @@ -[[!meta copyright="Copyright © 2009, 2010 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]]."]]"""]] - -The GNU Hurd uses a similar concept to [[UNIX processes|unix/process]]. - -As a [[Mach task|microkernel/mach/task]] only implements a part of a UNIX -process, there is additional work to be done, for example for [[signal]]s, -[[environment_variable]]s, [[file_descriptor]]s. - - -# Controlling TTY - -Hurd controlling tty behavior is generally consistent with BSD's, including -`TIOCSCTTY`. Linux also has `TIOCSCTTY` and it is harmless to use it there. -But BSD and Hurd never do an implicit `TIOCSCTTY` (hence our `O_NOCTTY` is -zero). - -C.f. <http://lists.gnu.org/archive/html/bug-hurd/2009-10/msg00030.html> and the -following messages. diff --git a/glibc/signal.mdwn b/glibc/signal.mdwn deleted file mode 100644 index 727247ac..00000000 --- a/glibc/signal.mdwn +++ /dev/null @@ -1,35 +0,0 @@ -[[!meta copyright="Copyright © 2009, 2010, 2011 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]]."]]"""]] - -The [[*UNIX signalling mechanism*|unix/signal]] is implemented for the GNU Hurd -by means of a separate *[[signal_thread]]* that is part of every user-space -[[process]]. This makes handling of signals a separate thread of control. -[[GNU Mach|microkernel/mach/gnumach]] itself has no idea what a signal is and -`kill` is not a [[system_call]] (as it typically is in a [[UNIX]] system): it's -implemented in [[glibc]]. - - * [[SA_SIGINFO, SA_SIGACTION|open_issues/sa_siginfo_sa_sigaction]] - - * Why does `kill` hang sometimes? - - <youpi> kill send the signal to the process - <youpi> if the process is hung, killing waits - <youpi> signals should be just asynchronous, but apparently for some - reason Roland & co wanted some synchronization - - [[!taglink open_issue_glibc]] - - -# Further Reading - - * {{$unix#djb_self-pipe}}. - - * {{$unix#rjk_fork}}. diff --git a/glibc/signal/signal_thread.mdwn b/glibc/signal/signal_thread.mdwn deleted file mode 100644 index 5341b1ab..00000000 --- a/glibc/signal/signal_thread.mdwn +++ /dev/null @@ -1,100 +0,0 @@ -[[!meta copyright="Copyright © 2011 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]]."]]"""]] - -For delivering a signal, Mach forwards an `msg_sig_post` message from the -invoker of `kill` to the target process. The target process' [[signal_thread]] -job is it to listen to such messages and to set up signal handler contexts in -other threads. - ---- - -[[!tag open_issue_documentation]] - - <braunr> bugs around signals are very tricky - <braunr> signals are actually the most hairy part of the hurd - <braunr> and the reason they're aynchronous is that they're handled by a - second thread - <braunr> (so yes, every process on the hurd has at least two threads) - <svante_> braunr: How to solve the asynch problem then if every process has - two threads? - <braunr> the easiest method would be to align ourselves on what most other - Unices do - <braunr> establish a "signal protocol" between kernel and userspace - <braunr> with a set of signal info in a table, most likely at the top of - the stack - <braunr> but this is explicitely what the original Mach developers didn't - want, and they were right IMO - <braunr> having two threads is very clean, but it creates incompatibilites - with what POSIX requires - <braunr> so there might be a radical choice to make here - <braunr> and i doubt we have the resources to make it happen - <svante_> What is the advantage of having two threads per process, a per - the original design? - <braunr> it's clean - <braunr> you don't have to define async-signal-safe functions - <braunr> it's like using sigwait() yourself in a separate thread, or - multiplexing them through signalfd() - <svante_> Regardless of the advantages, isn't two threads per process a - waste of resources? - <braunr> sure it is - <braunr> but does it really matter ? - <braunr> mach and the hurd were intended to be "hyperthreaded" - <braunr> so basically, a thread should consume only a few kernel resources - <braunr> in GNU Mach, it doesn't even consume a kernel stack because only - continuations are used - <braunr> and in userspace, it consumes 2 MiB of virtual memory, a few table - entries, and almost no CPU time - <svante_> What does "hyperthreaded" mean: Do you have a reference? - <braunr> in this context, it just means there are a lot of threads - <braunr> even back in the 90s, the expected number of threads could scale - up to the thousand - <braunr> today, it isn't much impressive any more - <braunr> but at the time, most systems didn't have LWPs yet - <braunr> and a process was very expensive - <svante_> Looks like I have some catching up to do: What is "continuations" - and LWP? Maybe I also need a reference to an overview on multi-threading. - <ArneBab> Lightweight process? - http://en.wikipedia.org/wiki/Light-weight_process - <braunr> svante_: that's a whole computer science domain of its own - <braunr> yes - <braunr> LWPs are another names for kernel threads usually - <braunr> continuations are a facility which allows a thread to store its - state, yield the processor to another thread, and when it's dispatched - again by the scheduler, it can resume with its saved state - <braunr> most current kernels support kernel preemption though - <braunr> which means their state is saved based on scheduler decisions - <braunr> unlike continuations where the thread voluntarily saves its state - <braunr> if you only have continuations, you can't have kernel preemption, - but you end up with one kernel stack per processor - <braunr> while the other model allows kernel preemption and requires one - kernel stack per thread - <svante_> I know resources are limited, but it looks like kernel preemption - would be nice to have. Is that too much for a GSoC student? - <braunr> it would require a lot of changes in obscure and sensitive parts - of the kernel - <braunr> and no, kernel preemption is something we don't actually need - <braunr> even current debian linux kernels are built without kernel - preemption - <braunr> and considering mach has hard limitations on its physical memory - management, increasing the amount of memory used for kernel stacks would - imply less available memory for the rest of the system - <svante_> Are these hard limits in mach difficult to change? - <braunr> yes - <braunr> consider mach difficult to change - <braunr> that's actually one of the goals of my stalled project - <braunr> which I hope to resume by the end of the year :/ - <svante_> Reading Wikipedia it looks like LWP are "kernel treads" and other - threads are "user threads" at least in IBM/AIX. LWP in Linux is a thread - sharing resources and in SunOS they are "user threads". Which is closest - for Hurd? - <braunr> i told you - <braunr> 14:09 < braunr> LWPs are another names for kernel threads usually - <svante_> Similar to to the IBM definition then? Sorry for not remembering - what I've been reading. diff --git a/glibc/startup.mdwn b/glibc/startup.mdwn deleted file mode 100644 index b7ab9d96..00000000 --- a/glibc/startup.mdwn +++ /dev/null @@ -1,20 +0,0 @@ -[[!meta copyright="Copyright © 2011 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]]."]]"""]] - -Be it statically or dynamically linked, the *startup* of glibc-based programs -is quite hairy on GNU Hurd systems. - -[[!taglink open_issue_documentation open_issue_glibc]] - - * [[!message-id "200103081944.f28JiDk00232@delius.kettenis.local"]] - - * [[!message-id "3B7BF2B1.1417CD84@alcor.concordia.ca"]] - - * [[!message-id "871xc9qv6y.wl@ulysses.g10code.de"]] |