[src/trunk]: src/lib/libc/dlfcn Avoid a dependency issue between pthread TLS ...

[joerg <joerg%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/eba47e0c3688
branches:  trunk
changeset: 763200:eba47e0c3688
user:      joerg <joerg%NetBSD.org@localhost>
date:      Sat Mar 12 21:55:09 2011 +0000

description:
Avoid a dependency issue between pthread TLS by using simple atomic
initialisation, possibly running the initialisation loop more than once.

diffstat:

 lib/libc/dlfcn/dlfcn_elf.c |  20 +++++++++++++++-----
 1 files changed, 15 insertions(+), 5 deletions(-)

diffs (59 lines):

diff -r 45b903d5d41d -r eba47e0c3688 lib/libc/dlfcn/dlfcn_elf.c
--- a/lib/libc/dlfcn/dlfcn_elf.c        Sat Mar 12 19:52:45 2011 +0000
+++ b/lib/libc/dlfcn/dlfcn_elf.c        Sat Mar 12 21:55:09 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: dlfcn_elf.c,v 1.8 2011/03/07 05:09:11 joerg Exp $      */
+/*     $NetBSD: dlfcn_elf.c,v 1.9 2011/03/12 21:55:09 joerg Exp $      */
 
 /*
  * Copyright (c) 2000 Takuya SHIOZAKI
@@ -27,14 +27,15 @@
 
 #include <sys/cdefs.h>
 #if defined(LIBC_SCCS) && !defined(lint)
-__RCSID("$NetBSD: dlfcn_elf.c,v 1.8 2011/03/07 05:09:11 joerg Exp $");
+__RCSID("$NetBSD: dlfcn_elf.c,v 1.9 2011/03/12 21:55:09 joerg Exp $");
 #endif /* LIBC_SCCS and not lint */
 
-#include "reentrant.h"
 #include "namespace.h"
+#include <sys/atomic.h>
 #include <elf.h>
 #include <errno.h>
 #include <string.h>
+#include <stdbool.h>
 
 #undef dlopen
 #undef dlclose
@@ -132,7 +133,6 @@
        return -1;
 }
 
-static once_t dl_iterate_phdr_once = ONCE_INITIALIZER;
 static const char *dlpi_name;
 static Elf_Addr dlpi_addr;
 static const Elf_Phdr *dlpi_phdr;
@@ -175,12 +175,22 @@
 dl_iterate_phdr(int (*callback)(struct dl_phdr_info *, size_t, void *),
     void *data)
 {
+       static bool setup_done;
        struct dl_phdr_info phdr_info;
 
        if (__auxinfo == NULL)
                return EOPNOTSUPP;
 
-       thr_once(&dl_iterate_phdr_once, dl_iterate_phdr_setup);
+       if (!setup_done) {
+               /*
+                * This can race on the first call to dl_iterate_phdr.
+                * dl_iterate_phdr_setup only touches field of pointer size
+                * and smaller and such stores are atomic.
+                */
+               dl_iterate_phdr_setup();
+               membar_producer();
+               setup_done = true;
+       }
 
        memset(&phdr_info, 0, sizeof(phdr_info));
        phdr_info.dlpi_addr = dlpi_addr;