[Bug testsuite/27690] FAIL: gdb.threads/check-libthread-db.exp: user-initiated check: libpthread.so not initialized (pattern 2)

["vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=27690

Tom de Vries <vries at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |simark at simark dot ca

--- Comment #3 from Tom de Vries <vries at gcc dot gnu.org> ---
Managed to bisect this in glibc, as follows.

I. 

Build glibc using pretty basic script:
...
$ more ~/glibc/scripts/build.sh
#!/bin/sh

set -e

pwd=$(pwd -P)

src=$pwd/src
build=$pwd/build
install=$pwd/install

rm -Rf $build $install
mkdir $build $install

cd $build

$src/configure --prefix=$install

make -j5
...

II.

Run test-case using custom build glibc (using recipe from
https://sourceware.org/glibc/wiki/Testing/Builds#Compile_against_glibc_build_tree):
...
diff --git a/gdb/testsuite/gdb.threads/check-libthread-db.exp
b/gdb/testsuite/gdb.threads/c
heck-libthread-db.exp
index dfb3bad3712..78bb881c6b3 100644
--- a/gdb/testsuite/gdb.threads/check-libthread-db.exp
+++ b/gdb/testsuite/gdb.threads/check-libthread-db.exp
@@ -27,15 +27,23 @@ if [gdb_debug_enabled] {

 standard_testfile

+set GLIBC "/home/vries/glibc/build"
+set f1
"-Wl,-rpath=${GLIBC}:${GLIBC}/math:${GLIBC}/elf:${GLIBC}/dlfcn:${GLIBC}/nss:
${GLIBC}/nis:${GLIBC}/rt:${GLIBC}/resolv:${GLIBC}/crypt:${GLIBC}/nptl:${GLIBC}/dfp" 
+
+set f2 "-Wl,--dynamic-linker=${GLIBC}/elf/ld.so"
+
 if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
-        executable debug] != "" } {
+        executable [list debug additional_flags=$f1 additional_flags=$f2]] !=
"" } {
     return -1
 }

+
 with_test_prefix "user-initiated check" {

     # User-initiated check with libthread_db not loaded.
     clean_restart ${binfile}
+    gdb_test "set auto-load safe-path /"
+    gdb_test "set libthread-db-search-path /home/vries/glibc/build/nptl_db"

     gdb_test "maint show check-libthread-db" \
        "Whether to check libthread_db at load time is off."
@@ -81,6 +89,8 @@ with_test_prefix "automated load-time check" {
     # Automated load-time check with NPTL uninitialized.
     with_test_prefix "libpthread.so not initialized" {
        clean_restart ${binfile}
+       gdb_test "set auto-load safe-path /"
+       gdb_test "set libthread-db-search-path /home/vries/glibc/build/nptl_db"

        gdb_test_no_output "maint set check-libthread-db 1"
        gdb_test_no_output "set debug libthread-db 1"
@@ -99,6 +109,8 @@ with_test_prefix "automated load-time check" {
     # Automated load-time check with NPTL fully operational.
     with_test_prefix "libpthread.so fully initialized" {
        clean_restart ${binfile}
+       gdb_test "set auto-load safe-path /"
+       gdb_test "set libthread-db-search-path /home/vries/glibc/build/nptl_db"

        gdb_test_no_output "maint set check-libthread-db 1"
        gdb_test_no_output "set debug libthread-db 1"
...

Bisects to (as indeed suggested here
https://sourceware.org/pipermail/gdb-patches/2021-July/180867.html by Simon):
...
$ git bisect bad
1daccf403b1bd86370eb94edca794dc106d02039 is the first bad commit
commit 1daccf403b1bd86370eb94edca794dc106d02039
Author: Florian Weimer <fweimer@redhat.com>
Date:   Mon Nov 16 19:33:30 2020 +0100

    nptl: Move stack list variables into _rtld_global
...

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