[PATCH v3] Destructor support for C++11 thread_local variables - abilist entries

[Siddhesh Poyarekar]

Hi,

Here is an updated patch based on feedback so far.  For context of this
change, please see the following thread:

http://sourceware.org/ml/libc-alpha/2012-10/msg00289.html

To summarize, this patch adds destructor support for the C++11
variables of the thread_local scope.  it adds a new function
__cxa_thread_atexit_impl, that libstdc++ calls to register destructors
for the thread_local objects it constructs.  The destructors will then
be called at either thread exit or program exit.  The current iteration
of the patch adds support to allow unloading a DSO that has
thread_local variables provided that all threads that constructed the
variables have exited and their destructors called.  This is
implemented by adding an extra field in struct link_map to count the
destructors that were registered, decrementing when a destructor is
called.

I have verified that the latter functionality works with the help of
the following program:

$ cat foo.cc:

#include "thread_local.h"
extern "C" void do_foo (void)
{
  thread_local A b;
}

$ cat thread_local.cc:

#include <dlfcn.h>
#include <pthread.h>
#include <stdio.h>
#include <unistd.h>
#include "thread_local.h"

int c;
int d;

void (*foo) (void);
pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;

void f()
{
  thread_local A a;
}

void *
load (void *u)
{
  pthread_mutex_lock (&m);
  void *h = dlopen ("./libfoo.so", RTLD_LAZY);
  foo = (void (*) (void)) dlsym(h, "do_foo");

  foo ();
  dlclose (h);
  pthread_mutex_unlock (&m);
}

void *
thr (void *u)
{
  /* wait till foo is initialized.  */
  while (!foo);   

  pthread_mutex_lock (&m);
  foo ();
  pthread_mutex_unlock (&m);
}

int main()
{

  pthread_t t, dsot;

  pthread_create (&t, NULL, thr, NULL);
  sleep (1);
  pthread_create (&dsot, NULL, load, NULL);

  pthread_join (t, NULL);
  pthread_join (dsot, NULL);
  printf ("%d, %d\n", c, d);
}

$ tls-g++ -g -fPIC -std=c++11 thread_local.cc -ldl -pthread
$ tls-g++ -fPIC -std=c++11 -shared -o libfoo.so foo.cc


Regards,
Siddhesh

ChangeLog:

	* include/link.h (struct link_map): New member l_tls_dtor_count.
	* include/stdlib.h (__cxa_thread_atexit_impl): Declare.
	(__call_tls_dtors): Likewise.
	* sysdeps/unix/sysv/linux/i386/nptl/libc.abilist: Add
	__cxa_thread_atexit_impl.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/nptl/libc.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libc.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/nptl/libc.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/nptl/libc.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/sh/nptl/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/nptl/libc.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/nptl/libc.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/x86_64/64/nptl/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/x32/nptl/libc.abilist:
	Likewise.
	* stdlib/Makefile (routines): Add __cxa_thread_atexit_impl.
	* stdlib/Versions (GLIBC_2.17): Likewise.
	(GLIBC_PRIVATE): Add __call_tls_dtors.
	* stdlib/cxa_thread_atexit_impl.c: New file with helper function
	for libstdc++.
	* stdlib/exit.c (__run_exit_handlers): Call __call_tls_dtors.

nptl/ChangeLog:

	* pthread_create.c (start_thread): Call __call_tls_dtors.

ChangeLog.alpha:
2012-10-11  Siddhesh Poyarekar  <siddhesh@redhat.com>

	* sysdeps/unix/sysv/linux/alpha/nptl/libc.abilist: Add
	__cxa_thread_atexit_impl.


ChangeLog.arm:
2012-10-11  Siddhesh Poyarekar  <siddhesh@redhat.com>

	* sysdeps/unix/sysv/linux/arm/nptl/libc.abilist: Add
	__cxa_thread_atexit_impl.


ChangeLog.ia64:
2012-10-11  Siddhesh Poyarekar  <siddhesh@redhat.com>

	* sysdeps/unix/sysv/linux/ia64/nptl/libc.abilist: Add
	__cxa_thread_atexit_impl.


ChangeLog.m68k:
2012-10-11  Siddhesh Poyarekar  <siddhesh@redhat.com>

	* sysdeps/unix/sysv/linux/m68k/coldfire/nptl/libc.abilist: Add
	__cxa_thread_atexit_impl.
	* sysdeps/unix/sysv/linux/m68k/m680x0/nptl/libc.abilist:
	Likewise.


ChangeLog.mips:
2012-10-11  Siddhesh Poyarekar  <siddhesh@redhat.com>

	* sysdeps/unix/sysv/linux/mips/mips32/nptl/libc.abilist: Add
	__cxa_thread_atexit_impl.
	* sysdeps/unix/sysv/linux/mips/mips64/n32/nptl/libc.abilist:
	Likewise.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: thread-local.patch
Type: text/x-patch
Size: 16505 bytes
Desc: not available
URL: <http://sourceware.org/pipermail/libc-alpha/attachments/20121017/ff58142f/attachment.bin>