diff options
Diffstat (limited to 'glibc')
| -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 | 63 | ||||
| -rw-r--r-- | glibc/poll.mdwn | 15 | ||||
| -rw-r--r-- | glibc/process.mdwn | 26 | ||||
| -rw-r--r-- | glibc/signal.mdwn | 31 |
7 files changed, 180 insertions, 0 deletions
diff --git a/glibc/environment_variable.mdwn b/glibc/environment_variable.mdwn new file mode 100644 index 00000000..76c1371e --- /dev/null +++ b/glibc/environment_variable.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 + + * [*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 --- /dev/null +++ b/glibc/fallocate.mdwn @@ -0,0 +1,17 @@ +[[!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 new file mode 100644 index 00000000..2c56d070 --- /dev/null +++ b/glibc/file_descriptor.mdwn @@ -0,0 +1,13 @@ +[[!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 new file mode 100644 index 00000000..496dc743 --- /dev/null +++ b/glibc/fork.mdwn @@ -0,0 +1,63 @@ +[[!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]]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]]). + + +## 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/process.mdwn b/glibc/process.mdwn new file mode 100644 index 00000000..9b2ec251 --- /dev/null +++ b/glibc/process.mdwn @@ -0,0 +1,26 @@ +[[!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 new file mode 100644 index 00000000..67028fef --- /dev/null +++ b/glibc/signal.mdwn @@ -0,0 +1,31 @@ +[[!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 [[*UNIX signalling mechanism*|unix/signal]] 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]] + + * 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}}. |