[PATCH] Create nptl manual node and document thread_local limitation

[Siddhesh Poyarekar <siddhesh at redhat dot com>]

Hi,

The patch below adds a chapter on threads and documents the fact that
destructors for thread-specific data created with pthread_key_create
should not use thread_local objects.

Siddhesh

	* manual/Makefile (chapters): Add nptl.
	* manual/debug.texi (Debugging Support): Add link to Threads
	chapter.
	* manual/nptl.texi: New file.

diff --git a/manual/Makefile b/manual/Makefile
index c1a304c..10314a9 100644
--- a/manual/Makefile
+++ b/manual/Makefile
@@ -42,7 +42,7 @@ chapters = $(addsuffix .texi, \
 		       message search pattern io stdio llio filesys	\
 		       pipe socket terminal syslog math arith time	\
 		       resource setjmp signal startup process job nss	\
-		       users sysinfo conf crypt debug)
+		       users sysinfo conf crypt debug nptl)
 add-chapters = $(wildcard $(foreach d, $(add-ons), ../$d/$d.texi))
 appendices = lang.texi header.texi install.texi maint.texi platform.texi \
 	     contrib.texi
diff --git a/manual/debug.texi b/manual/debug.texi
index b2bcb31..79dc70c 100644
--- a/manual/debug.texi
+++ b/manual/debug.texi
@@ -1,5 +1,5 @@
 @node Debugging Support
-@c @node Debugging Support, , Cryptographic Functions, Top
+@c @node Debugging Support, Threads, Cryptographic Functions, Top
 @c %MENU% Functions to help debugging applications
 @chapter Debugging support
 
diff --git a/manual/nptl.texi b/manual/nptl.texi
new file mode 100644
index 0000000..11112bd
--- /dev/null
+++ b/manual/nptl.texi
@@ -0,0 +1,33 @@
+@node Threads
+@c @node Threads, , Cryptographic Functions, Top
+@chapter Threads
+@c %MENU% Threads
+@cindex pthreads
+
+This chapter describes the the glibc pthread implementation.
+
+@menu
+* Pthread Thread-specific Data::  Pthreads support for creating and
+				  managing thread-specific data
+@end menu
+
+@node Pthread Thread-specific Data
+@section Pthread Thread-specific Data
+
+@theglibc{} implements functions to allow users to create and manage
+data specific to a thread.  Such data may be destroyed on thread exit,
+if a destructor is provided.  The following functions are defined:
+
+@table @code
+
+@item int pthread_key_create(pthread_key_t *@var{key}, void (*@var{destructor})(void*))
+Create a thread-specific data (TSD) object for the calling thread, referenced
+by the key @var{key}.  On exit of the calling thread, @var{destructor} is
+called with @var{key} as the argument.
+
+Objects declared with the C++11 @code{thread_local} keyword are destroyed
+before TSD, so they should not be used in pthread thread-specific data
+destructors or even as members of the TSD, since the latter is always passed
+as an argument to the destructor function.
+
+@end table