Add definitions for Process and (finally!) Thread

Tweak some error descriptions based on that
Completely reword ETXTBSY description based on a suggestion from millert@

tweaks and oks jmc@ millert@ sobrado@

1 files changed, 28 insertions, 9 deletions

diff --git a/lib/libc/sys/intro.2 b/lib/libc/sys/intro.2
index 80456dc09ff..460a75aff28 100644
--- a/lib/libc/sys/intro.2
+++ b/lib/libc/sys/intro.2
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: intro.2,v 1.50 2014/05/02 20:20:12 guenther Exp $
+.\"	$OpenBSD: intro.2,v 1.51 2014/05/30 04:42:07 guenther Exp $
 .\"	$NetBSD: intro.2,v 1.6 1995/02/27 12:33:41 cgd Exp $
 .\"
 .\" Copyright (c) 1980, 1983, 1986, 1991, 1993
@@ -30,7 +30,7 @@
 .\"
 .\"     @(#)intro.2	8.3 (Berkeley) 12/11/93
 .\"
-.Dd $Mdocdate: May 2 2014 $
+.Dd $Mdocdate: May 30 2014 $
 .Dt INTRO 2
 .Os
 .Sh NAME
@@ -92,7 +92,7 @@ An asynchronous signal (such as
 .Dv SIGINT
 or
 .Dv SIGQUIT )
-was caught by the process during the execution of an interruptible
+was caught by the thread during the execution of an interruptible
 function.
 If the signal handler performs a normal return, the
 interrupted function call will seem to have returned the error condition.
@@ -187,11 +187,10 @@ A control function (see
 was attempted for a file or
 special device for which the operation was inappropriate.
 .It Er 26 ETXTBSY Em "Text file busy" .
-The new process was a pure procedure (shared text) file
-which was open for writing by another process, or
-while the pure procedure file was being executed an
-.Xr open 2
-call requested write access.
+An attempt was made either to execute a pure procedure (shared text)
+file which was open for writing by another process,
+or to open with write access a pure procedure file that is currently
+being executed.
 .It Er 27 EFBIG Em "File too large" .
 The size of a file exceeded the maximum.
 (The system-wide maximum file size is 2**63 bytes.
@@ -427,7 +426,7 @@ caller provided space.
 .It Er 88 ECANCELED Em "Operation canceled" .
 The requested operation was canceled.
 .It Er 89 EIDRM Em "Identifier removed" .
-An IPC identifier was removed while the current process was waiting on it.
+An IPC identifier was removed while the current thread was waiting on it.
 .It Er 90 ENOMSG Em "\&No message of desired type".
 An IPC message queue does not contain a message of the desired type,
 or a message catalog does not contain the requested message.
@@ -436,6 +435,12 @@ The operation has requested an unsupported value.
 .El
 .Sh DEFINITIONS
 .Bl -tag -width Ds
+.It Process
+A process is a collection of one or more threads,
+plus the resources shared by those threads such as process ID,
+address space,
+user IDs and group IDs,
+and root directory and current working directory.
 .It Process ID
 Each active process in the system is uniquely identified by a non-negative
 integer called a process ID.
@@ -498,6 +503,20 @@ which is in a separate session.
 Not all members of an orphaned process group are necessarily orphaned
 processes (those whose creating process has exited).
 The process group of a session leader is orphaned by definition.
+.It Thread
+A thread is a preemptively scheduled flow of control within a process,
+with its own set of register values,
+floating point environment,
+thread ID,
+signal mask,
+pending signal set,
+alternate signal stack,
+thread control block address,
+resource utilization,
+errno variable location,
+and values for thread-specific keys.
+A process initially has just one thread,
+a duplicate of the thread in the parent process that created this process.
 .It Real User ID and Real Group ID
 Each user on the system is identified by a positive integer
 termed the real user ID.