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authorSiddhesh Poyarekar <siddhesh@redhat.com>2013-02-18 19:08:21 +0530
committerSiddhesh Poyarekar <siddhesh@redhat.com>2013-02-18 19:08:21 +0530
commitba384f6ed9275f3966505f2375b56d169e3dc588 (patch)
treed832a5a24bab934c946089b8d2a9a16f1766470d /stdlib
parentffaa74cf68a370e232279a9a9b0a02ade287cc99 (diff)
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C++11 thread_local destructors support
This feature is specifically for the C++ compiler to offload calling thread_local object destructors on thread program exit, to glibc. This is to overcome the possible complication of destructors of thread_local objects getting called after the DSO in which they're defined is unloaded by the dynamic linker. The DSO is marked as 'unloadable' if it has a constructed thread_local object and marked as 'unloadable' again when all the constructed thread_local objects defined in it are destroyed.
Diffstat (limited to 'stdlib')
-rw-r--r--stdlib/Makefile12
-rw-r--r--stdlib/Versions4
-rw-r--r--stdlib/cxa_thread_atexit_impl.c102
-rw-r--r--stdlib/exit.c3
-rw-r--r--stdlib/tst-tls-atexit-lib.c36
-rw-r--r--stdlib/tst-tls-atexit.c111
6 files changed, 266 insertions, 2 deletions
diff --git a/stdlib/Makefile b/stdlib/Makefile
index e2078f8877..6f98c71c64 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -34,7 +34,7 @@ routines := \
bsearch qsort msort \
getenv putenv setenv secure-getenv \
exit on_exit atexit cxa_atexit cxa_finalize old_atexit \
- quick_exit at_quick_exit cxa_at_quick_exit \
+ quick_exit at_quick_exit cxa_at_quick_exit cxa_thread_atexit_impl \
abs labs llabs \
div ldiv lldiv \
mblen mbstowcs mbtowc wcstombs wctomb \
@@ -71,9 +71,11 @@ tests := tst-strtol tst-strtod testmb testrand testsort testdiv \
tst-makecontext2 tst-strtod6 tst-unsetenv1 \
tst-makecontext3 bug-getcontext bug-fmtmsg1 \
tst-secure-getenv tst-strtod-overflow tst-strtod-round \
- tst-tininess tst-strtod-underflow
+ tst-tininess tst-strtod-underflow tst-tls-atexit
tests-static := tst-secure-getenv
+modules-names = tst-tls-atexit-lib
+
include ../Makeconfig
ifeq ($(build-shared),yes)
@@ -155,3 +157,9 @@ $(objpfx)bug-getcontext: $(link-libm)
$(objpfx)tst-strtod-round: $(link-libm)
$(objpfx)tst-tininess: $(link-libm)
$(objpfx)tst-strtod-underflow: $(link-libm)
+
+tst-tls-atexit-lib.so-no-z-defs = yes
+
+LDFLAGS-tst-tls-atexit = $(common-objpfx)nptl/libpthread.so \
+ $(common-objpfx)dlfcn/libdl.so
+$(objpfx)tst-tls-atexit.out: $(objpfx)tst-tls-atexit-lib.so
diff --git a/stdlib/Versions b/stdlib/Versions
index 250bd5fad7..f1777dfcf4 100644
--- a/stdlib/Versions
+++ b/stdlib/Versions
@@ -106,6 +106,9 @@ libc {
GLIBC_2.17 {
secure_getenv;
}
+ GLIBC_2.18 {
+ __cxa_thread_atexit_impl;
+ }
GLIBC_PRIVATE {
# functions which have an additional interface since they are
# are cancelable.
@@ -114,5 +117,6 @@ libc {
__abort_msg;
# Used from other libraries
__libc_secure_getenv;
+ __call_tls_dtors;
}
}
diff --git a/stdlib/cxa_thread_atexit_impl.c b/stdlib/cxa_thread_atexit_impl.c
new file mode 100644
index 0000000000..9638efc7a0
--- /dev/null
+++ b/stdlib/cxa_thread_atexit_impl.c
@@ -0,0 +1,102 @@
+/* Register destructors for C++ TLS variables declared with thread_local.
+ Copyright (C) 2012 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#include <stdlib.h>
+#include <ldsodefs.h>
+
+typedef void (*dtor_func) (void *);
+
+struct dtor_list
+{
+ dtor_func func;
+ void *obj;
+ struct link_map *map;
+ struct dtor_list *next;
+};
+
+static __thread struct dtor_list *tls_dtor_list;
+static __thread void *dso_symbol_cache;
+static __thread struct link_map *lm_cache;
+
+/* Register a destructor for TLS variables declared with the 'thread_local'
+ keyword. This function is only called from code generated by the C++
+ compiler. FUNC is the destructor function and OBJ is the object to be
+ passed to the destructor. DSO_SYMBOL is the __dso_handle symbol that each
+ DSO has at a unique address in its map, added from crtbegin.o during the
+ linking phase. */
+int
+__cxa_thread_atexit_impl (dtor_func func, void *obj, void *dso_symbol)
+{
+ /* Prepend. */
+ struct dtor_list *new = calloc (1, sizeof (struct dtor_list));
+ new->func = func;
+ new->obj = obj;
+ new->next = tls_dtor_list;
+ tls_dtor_list = new;
+
+ /* See if we already encountered the DSO. */
+ __rtld_lock_lock_recursive (GL(dl_load_lock));
+
+ if (__builtin_expect (dso_symbol_cache != dso_symbol, 0))
+ {
+ ElfW(Addr) caller = (ElfW(Addr)) dso_symbol;
+
+ struct link_map *l = _dl_find_dso_for_object (caller);
+
+ /* If the address is not recognized the call comes from the main
+ program (we hope). */
+ lm_cache = l ? l : GL(dl_ns)[LM_ID_BASE]._ns_loaded;
+ }
+ /* A destructor could result in a thread_local construction and the former
+ could have cleared the flag. */
+ if (lm_cache->l_type == lt_loaded && lm_cache->l_tls_dtor_count == 0)
+ lm_cache->l_flags_1 |= DF_1_NODELETE;
+
+ new->map = lm_cache;
+ new->map->l_tls_dtor_count++;
+
+ __rtld_lock_unlock_recursive (GL(dl_load_lock));
+
+ return 0;
+}
+
+/* Call the destructors. This is called either when a thread returns from the
+ initial function or when the process exits via the exit(3) function. */
+void
+__call_tls_dtors (void)
+{
+ while (tls_dtor_list)
+ {
+ struct dtor_list *cur = tls_dtor_list;
+ tls_dtor_list = tls_dtor_list->next;
+
+ cur->func (cur->obj);
+
+ __rtld_lock_lock_recursive (GL(dl_load_lock));
+
+ /* Allow DSO unload if count drops to zero. */
+ cur->map->l_tls_dtor_count--;
+ if (cur->map->l_tls_dtor_count == 0 && cur->map->l_type == lt_loaded)
+ cur->map->l_flags_1 &= ~DF_1_NODELETE;
+
+ __rtld_lock_unlock_recursive (GL(dl_load_lock));
+
+ free (cur);
+ }
+}
+libc_hidden_def (__call_tls_dtors)
diff --git a/stdlib/exit.c b/stdlib/exit.c
index e9a2139f4e..2e86caa2d4 100644
--- a/stdlib/exit.c
+++ b/stdlib/exit.c
@@ -33,6 +33,9 @@ attribute_hidden
__run_exit_handlers (int status, struct exit_function_list **listp,
bool run_list_atexit)
{
+ /* First, call the TLS destructors. */
+ __call_tls_dtors ();
+
/* We do it this way to handle recursive calls to exit () made by
the functions registered with `atexit' and `on_exit'. We call
everyone on the list and use the status value in the last
diff --git a/stdlib/tst-tls-atexit-lib.c b/stdlib/tst-tls-atexit-lib.c
new file mode 100644
index 0000000000..aab28bb607
--- /dev/null
+++ b/stdlib/tst-tls-atexit-lib.c
@@ -0,0 +1,36 @@
+/* Verify that DSO is unloaded only if its TLS objects are destroyed - the DSO.
+ Copyright (C) 2012 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+extern void *__dso_handle;
+
+typedef struct
+{
+ void *val;
+} A;
+
+/* We only care about the destructor. */
+void A_dtor (void *obj)
+{
+ ((A *)obj)->val = obj;
+}
+
+void do_foo (void)
+{
+ static __thread A b;
+ __cxa_thread_atexit_impl (A_dtor, &b, __dso_handle);
+}
diff --git a/stdlib/tst-tls-atexit.c b/stdlib/tst-tls-atexit.c
new file mode 100644
index 0000000000..b7312cbc84
--- /dev/null
+++ b/stdlib/tst-tls-atexit.c
@@ -0,0 +1,111 @@
+/* Verify that DSO is unloaded only if its TLS objects are destroyed.
+ Copyright (C) 2012 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+/* There are two tests in this test case. The first is implicit where it is
+ assumed that the destructor call on exit of the LOAD function does not
+ segfault. The other is a verification that after the thread has exited, a
+ dlclose will unload the DSO. */
+
+#include <dlfcn.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+
+void *handle;
+pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
+
+void *
+load (void *u)
+{
+ pthread_mutex_lock (&m);
+ handle = dlopen ("$ORIGIN/tst-tls-atexit-lib.so", RTLD_LAZY);
+ if (!handle)
+ {
+ printf ("Unable to load DSO: %s\n", dlerror ());
+ return (void *) (uintptr_t) 1;
+ }
+
+ void (*foo) (void) = (void (*) (void)) dlsym(handle, "do_foo");
+
+ if (!foo)
+ {
+ printf ("Unable to find symbol: %s\n", dlerror ());
+ exit (1);
+ }
+
+ foo ();
+
+ /* This should not unload the DSO. If it does, then the thread exit will
+ result in a segfault. */
+ dlclose (handle);
+ pthread_mutex_unlock (&m);
+
+ return NULL;
+}
+
+int
+main (void)
+{
+ pthread_t t;
+ int ret;
+ void *thr_ret;
+
+ if ((ret = pthread_create (&t, NULL, load, NULL)) != 0)
+ {
+ printf ("pthread_create failed: %s\n", strerror (ret));
+ return 1;
+ }
+
+ if ((ret = pthread_join (t, &thr_ret)) != 0)
+ {
+ printf ("pthread_create failed: %s\n", strerror (ret));
+ return 1;
+ }
+
+ if (thr_ret != NULL)
+ return 1;
+
+ /* Now this should unload the DSO. */
+ dlclose (handle);
+
+ /* Run through our maps and ensure that the DSO is unloaded. */
+ FILE *f = fopen ("/proc/self/maps", "r");
+
+ if (f == NULL)
+ {
+ perror ("Failed to open /proc/self/maps");
+ fprintf (stderr, "Skipping verification of DSO unload\n");
+ return 0;
+ }
+
+ char *line = NULL;
+ size_t s = 0;
+ while (getline (&line, &s, f) > 0)
+ {
+ if (strstr (line, "tst-tls-atexit-lib.so"))
+ {
+ printf ("DSO not unloaded yet:\n%s", line);
+ return 1;
+ }
+ }
+ free (line);
+
+ return 0;
+}