Merge branch 'master' into external_pager_mechanism

Conflicts:
	microkernel/mach/external_pager_mechanism.mdwn

5 files changed, 143 insertions, 0 deletions

diff --git a/glibc/environment_variables.mdwn b/glibc/environment_variables.mdwn
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+[[!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
new file mode 100644
index 00000000..3aecf16b
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+++ b/glibc/fallocate.mdwn
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+[[!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/fork.mdwn b/glibc/fork.mdwn
new file mode 100644
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--- /dev/null
+++ b/glibc/fork.mdwn
@@ -0,0 +1,64 @@
+[[!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]]."]]"""]]
+
+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]] for each of them.
+
+In 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]]).
+
+
+## Related
+
+  * [[open_issues/secure_file_descriptor_handling]].
+
+
+# External
+
+  * {{$unix#djb_self-pipe}}.
+
+  * {{$unix#rjk_fork}}.
diff --git a/glibc/poll.mdwn b/glibc/poll.mdwn
new file mode 100644
index 00000000..d96f27a5
--- /dev/null
+++ b/glibc/poll.mdwn
@@ -0,0 +1,15 @@
+[[!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/signals.mdwn b/glibc/signals.mdwn
new file mode 100644
index 00000000..40fdc0e1
--- /dev/null
+++ b/glibc/signals.mdwn
@@ -0,0 +1,32 @@
+[[!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]]."]]"""]]
+
+*[[UNIX]] signals* are a means to asynchronously invoke a specific function
+(*signal handler*).  This may impact on [[system call]]s that are executing at
+the same time in that they may be completely aborted, return incomplete
+results, scheduled for restarting, or cause signal delivery to be blocked upon
+the system call's completion.
+
+An explanation can be found in the relevant standards, an overview, including
+UNIX signals' deficiencies is given in {{$unix#2010_brown_ghosts_3}}, for
+example.
+
+The UNIX signalling mechanism is implemented for the GNU Hurd by means of a
+separate signal-handling thread that is part of every process.  This makes
+handling of signals a separate thread of control.
+
+  * [[SA_SIGINFO, SA_SIGACTION|open_issues/sa_siginfo_sa_sigaction]]
+
+
+# External
+
+  * {{$unix#djb_self-pipe}}.
+
+  * {{$unix#rjk_fork}}.