diff --git a/Makefile.am b/Makefile.am
index 2ee81bd..7a179d8 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -17,8 +17,9 @@
 # <https://www.gnu.org/licenses/>.
 
 SUBDIRS = tests
-AM_CXXFLAGS = -std=c++11 -Wall -Wextra -pedantic
+AM_CXXFLAGS = $(PTHREAD_CFLAGS) -std=c++11 -Wall -Wextra -pedantic
+LIBS = $(PTHREAD_LIBS)
 
 bin_PROGRAMS = termux-elf-cleaner
 
-termux_elf_cleaner_SOURCES = elf-cleaner.cpp arghandling.c
+termux_elf_cleaner_SOURCES = elf-cleaner.cpp arghandling.c cpucount.c
diff --git a/README.md b/README.md
index ec30504..07a364a 100644
--- a/README.md
+++ b/README.md
@@ -56,6 +56,8 @@ Options:
 
 SPDX-License-Identifier: [GPL-3.0-or-later](https://spdx.org/licenses/GPL-3.0-or-later.html)
 
+License is GPL-3.0-or-later in all source files unless specified otherwise in file header. 
+
 ## See also
 
 * [Bionic's related docs](https://android.googlesource.com/platform/bionic/+/refs/heads/master/android-changes-for-ndk-developers.md)
diff --git a/configure.ac b/configure.ac
index 2ae8b7b..c6aa21f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -31,6 +31,10 @@ AC_PROG_CC
 AC_PROG_CXX
 AC_LANG(C++)
 
+AC_CONFIG_MACRO_DIR([m4])
+
+AX_PTHREAD
+
 copyright="Copyright (C) 2022 Termux."
 AC_DEFINE_UNQUOTED(COPYRIGHT, ["$copyright"],
   [Short copyright string for this version of termux-elf-cleaner.])
diff --git a/cpucount.c b/cpucount.c
new file mode 100644
index 0000000..998daf3
--- /dev/null
+++ b/cpucount.c
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: CC0-1.0
+
+/* Based on cpucount.c from github.com/cathugger/mkp224o */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+
+static int parsecpuinfo(void)
+{
+	unsigned char cpubitmap[128];
+
+	memset(cpubitmap,0,sizeof(cpubitmap));
+
+	FILE *f = fopen("/proc/cpuinfo","r");
+	if (!f)
+		return -1;
+
+	char buf[8192];
+	while (fgets(buf,sizeof(buf),f)) {
+		// we don't like newlines
+		for (char *p = buf;*p;++p) {
+			if (*p == '\n') {
+				*p = 0;
+				break;
+			}
+		}
+		// split ':'
+		char *v = 0;
+		for (char *p = buf;*p;++p) {
+			if (*p == ':') {
+				*p = 0;
+				v = p + 1;
+				break;
+			}
+		}
+		// key padding
+		size_t kl = strlen(buf);
+		while (kl > 0 && (buf[kl - 1] == '\t' || buf[kl - 1] == ' ')) {
+			--kl;
+			buf[kl] = 0;
+		}
+		// space before value
+		if (v) {
+			while (*v && (*v == ' ' || *v == '\t'))
+				++v;
+		}
+		// check what we need
+		if (strcasecmp(buf,"processor") == 0 && v) {
+			char *endp = 0;
+			long n = strtol(v,&endp,10);
+			if (endp && endp > v && n >= 0 && (size_t)n < sizeof(cpubitmap) * 8)
+				cpubitmap[n / 8] |= 1 << (n % 8);
+		}
+	}
+
+	fclose(f);
+
+	// count bits in bitmap
+	int ncpu = 0;
+	for (size_t n = 0;n < sizeof(cpubitmap) * 8;++n)
+		if (cpubitmap[n / 8] & (1 << (n % 8)))
+			++ncpu;
+
+	return ncpu;
+}
+
+int cpucount(void)
+{
+	int ncpu;
+	ncpu = parsecpuinfo();
+	if (ncpu > 0)
+		return ncpu;
+	return -1;
+}
diff --git a/cpucount.h b/cpucount.h
new file mode 100644
index 0000000..44caa8e
--- /dev/null
+++ b/cpucount.h
@@ -0,0 +1,2 @@
+extern "C" int
+cpucount(void);
diff --git a/elf-cleaner.cpp b/elf-cleaner.cpp
index 144be0f..356c1ae 100644
--- a/elf-cleaner.cpp
+++ b/elf-cleaner.cpp
@@ -21,6 +21,7 @@ along with termux-elf-cleaner.  If not, see
 
 #include <algorithm>
 #include <fcntl.h>
+#include <pthread.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -28,9 +29,10 @@ along with termux-elf-cleaner.  If not, see
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
+#include <vector>
 
 #include "arghandling.h"
-
+#include "cpucount.h"
 // Include a local elf.h copy as not all platforms have it.
 #include "elf.h"
 
@@ -55,6 +57,11 @@ int api_level = 21;
 bool dry_run = false;
 bool quiet = false;
 
+struct thread_data {
+	int argc = 0;
+	char **argv;
+};
+
 static char const *const usage_message[] =
 { "\
 \n\
@@ -65,6 +72,7 @@ Options:\n\
 \n\
 --api-level NN        choose target api level, i.e. 21, 24, ..\n\
 --dry-run             print info but but do not remove entries\n\
+--jobs N              allow N jobs, defaults to $(ncproc)\n\
 --quiet               do not print info about removed entries\n\
 --help                display this help and exit\n\
 --version             output version information and exit\n"
@@ -299,6 +307,18 @@ int parse_file(const char *file_name)
 	return 0;
 }
 
+void *file_parse_loop(void *td)
+{
+	struct thread_data *data = (struct thread_data *) td;
+	for (int i = 0; i < data->argc; i++) {
+		char *file_name = (*data).argv[i];
+		int ret = parse_file(file_name);
+		if (ret != 0)
+			break;
+	}
+	return NULL;
+}
+
 int main(int argc, char **argv)
 {
 	int skip_args = 0;
@@ -328,15 +348,50 @@ int main(int argc, char **argv)
 		supported_dt_flags_1 = (DF_1_NOW | DF_1_GLOBAL | DF_1_NODELETE);
 	}
 
+	int num_threads = cpucount();
+	argmatch(argv, argc, "-jobs", "--jobs", 1, &num_threads, &skip_args);
+	if (num_threads <= 0)
+		num_threads = 1;
+
 	if (argmatch(argv, argc, "-dry-run", "--dry-run", 3, NULL, &skip_args))
 		dry_run = true;
 
 	if (argmatch(argv, argc, "-quiet", "--quiet", 3, NULL, &skip_args))
 		quiet = true;
 
-	for (int i = skip_args+1; i < argc; i++) {
-		if (parse_file(argv[i]) != 0)
-			return 1;
+	std::vector<pthread_t> thread(num_threads);
+	std::vector<struct thread_data> data(num_threads);
+	int num_files = argc - (skip_args+1);
+	/* Tasks per thread, rounded down */
+	int tasks_per_thread = (num_files / num_threads);
+
+	for (int i = 0; i<num_threads; i++) {
+		if (i < num_files % num_threads) {
+			/* Distribute 'extra' jobs (since we rounded
+			   down tasks_per_thread) */
+			data[i].argv = &argv[skip_args+1];
+			data[i].argc = tasks_per_thread + 1;
+			skip_args += tasks_per_thread + 1;
+		} else {
+			data[i].argv = &argv[skip_args+1];
+			data[i].argc = tasks_per_thread;
+			skip_args += tasks_per_thread;
+		}
+	}
+
+	/* Launch Threads */
+	for (int i = 0; i<num_threads; i++) {
+		if (data[i].argc == 0)
+			break;
+		pthread_create(&thread[i], NULL, &file_parse_loop, &data[i]);
 	}
+
+	/* Wait for Threads to Finish */
+	for (int i = 0; i<num_threads; i++) {
+		if (data[i].argc == 0)
+			break;
+		pthread_join(thread[i], NULL);
+	}
+
 	return 0;
 }
diff --git a/m4/ax_pthread.m4 b/m4/ax_pthread.m4
new file mode 100644
index 0000000..9f35d13
--- /dev/null
+++ b/m4/ax_pthread.m4
@@ -0,0 +1,522 @@
+# ===========================================================================
+#        https://www.gnu.org/software/autoconf-archive/ax_pthread.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_PTHREAD([ACTION-IF-FOUND[, ACTION-IF-NOT-FOUND]])
+#
+# DESCRIPTION
+#
+#   This macro figures out how to build C programs using POSIX threads. It
+#   sets the PTHREAD_LIBS output variable to the threads library and linker
+#   flags, and the PTHREAD_CFLAGS output variable to any special C compiler
+#   flags that are needed. (The user can also force certain compiler
+#   flags/libs to be tested by setting these environment variables.)
+#
+#   Also sets PTHREAD_CC and PTHREAD_CXX to any special C compiler that is
+#   needed for multi-threaded programs (defaults to the value of CC
+#   respectively CXX otherwise). (This is necessary on e.g. AIX to use the
+#   special cc_r/CC_r compiler alias.)
+#
+#   NOTE: You are assumed to not only compile your program with these flags,
+#   but also to link with them as well. For example, you might link with
+#   $PTHREAD_CC $CFLAGS $PTHREAD_CFLAGS $LDFLAGS ... $PTHREAD_LIBS $LIBS
+#   $PTHREAD_CXX $CXXFLAGS $PTHREAD_CFLAGS $LDFLAGS ... $PTHREAD_LIBS $LIBS
+#
+#   If you are only building threaded programs, you may wish to use these
+#   variables in your default LIBS, CFLAGS, and CC:
+#
+#     LIBS="$PTHREAD_LIBS $LIBS"
+#     CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+#     CXXFLAGS="$CXXFLAGS $PTHREAD_CFLAGS"
+#     CC="$PTHREAD_CC"
+#     CXX="$PTHREAD_CXX"
+#
+#   In addition, if the PTHREAD_CREATE_JOINABLE thread-attribute constant
+#   has a nonstandard name, this macro defines PTHREAD_CREATE_JOINABLE to
+#   that name (e.g. PTHREAD_CREATE_UNDETACHED on AIX).
+#
+#   Also HAVE_PTHREAD_PRIO_INHERIT is defined if pthread is found and the
+#   PTHREAD_PRIO_INHERIT symbol is defined when compiling with
+#   PTHREAD_CFLAGS.
+#
+#   ACTION-IF-FOUND is a list of shell commands to run if a threads library
+#   is found, and ACTION-IF-NOT-FOUND is a list of commands to run it if it
+#   is not found. If ACTION-IF-FOUND is not specified, the default action
+#   will define HAVE_PTHREAD.
+#
+#   Please let the authors know if this macro fails on any platform, or if
+#   you have any other suggestions or comments. This macro was based on work
+#   by SGJ on autoconf scripts for FFTW (http://www.fftw.org/) (with help
+#   from M. Frigo), as well as ac_pthread and hb_pthread macros posted by
+#   Alejandro Forero Cuervo to the autoconf macro repository. We are also
+#   grateful for the helpful feedback of numerous users.
+#
+#   Updated for Autoconf 2.68 by Daniel Richard G.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Steven G. Johnson <stevenj@alum.mit.edu>
+#   Copyright (c) 2011 Daniel Richard G. <skunk@iSKUNK.ORG>
+#   Copyright (c) 2019 Marc Stevens <marc.stevens@cwi.nl>
+#
+#   This program is free software: you can redistribute it and/or modify it
+#   under the terms of the GNU General Public License as published by the
+#   Free Software Foundation, either version 3 of the License, or (at your
+#   option) any later version.
+#
+#   This program 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 General
+#   Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License along
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
+#
+#   As a special exception, the respective Autoconf Macro's copyright owner
+#   gives unlimited permission to copy, distribute and modify the configure
+#   scripts that are the output of Autoconf when processing the Macro. You
+#   need not follow the terms of the GNU General Public License when using
+#   or distributing such scripts, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+
+#serial 31
+
+AU_ALIAS([ACX_PTHREAD], [AX_PTHREAD])
+AC_DEFUN([AX_PTHREAD], [
+AC_REQUIRE([AC_CANONICAL_HOST])
+AC_REQUIRE([AC_PROG_CC])
+AC_REQUIRE([AC_PROG_SED])
+AC_LANG_PUSH([C])
+ax_pthread_ok=no
+
+# We used to check for pthread.h first, but this fails if pthread.h
+# requires special compiler flags (e.g. on Tru64 or Sequent).
+# It gets checked for in the link test anyway.
+
+# First of all, check if the user has set any of the PTHREAD_LIBS,
+# etcetera environment variables, and if threads linking works using
+# them:
+if test "x$PTHREAD_CFLAGS$PTHREAD_LIBS" != "x"; then
+        ax_pthread_save_CC="$CC"
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        AS_IF([test "x$PTHREAD_CC" != "x"], [CC="$PTHREAD_CC"])
+        AS_IF([test "x$PTHREAD_CXX" != "x"], [CXX="$PTHREAD_CXX"])
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+        AC_MSG_CHECKING([for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS])
+        AC_LINK_IFELSE([AC_LANG_CALL([], [pthread_join])], [ax_pthread_ok=yes])
+        AC_MSG_RESULT([$ax_pthread_ok])
+        if test "x$ax_pthread_ok" = "xno"; then
+                PTHREAD_LIBS=""
+                PTHREAD_CFLAGS=""
+        fi
+        CC="$ax_pthread_save_CC"
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+fi
+
+# We must check for the threads library under a number of different
+# names; the ordering is very important because some systems
+# (e.g. DEC) have both -lpthread and -lpthreads, where one of the
+# libraries is broken (non-POSIX).
+
+# Create a list of thread flags to try. Items with a "," contain both
+# C compiler flags (before ",") and linker flags (after ","). Other items
+# starting with a "-" are C compiler flags, and remaining items are
+# library names, except for "none" which indicates that we try without
+# any flags at all, and "pthread-config" which is a program returning
+# the flags for the Pth emulation library.
+
+ax_pthread_flags="pthreads none -Kthread -pthread -pthreads -mthreads pthread --thread-safe -mt pthread-config"
+
+# The ordering *is* (sometimes) important.  Some notes on the
+# individual items follow:
+
+# pthreads: AIX (must check this before -lpthread)
+# none: in case threads are in libc; should be tried before -Kthread and
+#       other compiler flags to prevent continual compiler warnings
+# -Kthread: Sequent (threads in libc, but -Kthread needed for pthread.h)
+# -pthread: Linux/gcc (kernel threads), BSD/gcc (userland threads), Tru64
+#           (Note: HP C rejects this with "bad form for `-t' option")
+# -pthreads: Solaris/gcc (Note: HP C also rejects)
+# -mt: Sun Workshop C (may only link SunOS threads [-lthread], but it
+#      doesn't hurt to check since this sometimes defines pthreads and
+#      -D_REENTRANT too), HP C (must be checked before -lpthread, which
+#      is present but should not be used directly; and before -mthreads,
+#      because the compiler interprets this as "-mt" + "-hreads")
+# -mthreads: Mingw32/gcc, Lynx/gcc
+# pthread: Linux, etcetera
+# --thread-safe: KAI C++
+# pthread-config: use pthread-config program (for GNU Pth library)
+
+case $host_os in
+
+        freebsd*)
+
+        # -kthread: FreeBSD kernel threads (preferred to -pthread since SMP-able)
+        # lthread: LinuxThreads port on FreeBSD (also preferred to -pthread)
+
+        ax_pthread_flags="-kthread lthread $ax_pthread_flags"
+        ;;
+
+        hpux*)
+
+        # From the cc(1) man page: "[-mt] Sets various -D flags to enable
+        # multi-threading and also sets -lpthread."
+
+        ax_pthread_flags="-mt -pthread pthread $ax_pthread_flags"
+        ;;
+
+        openedition*)
+
+        # IBM z/OS requires a feature-test macro to be defined in order to
+        # enable POSIX threads at all, so give the user a hint if this is
+        # not set. (We don't define these ourselves, as they can affect
+        # other portions of the system API in unpredictable ways.)
+
+        AC_EGREP_CPP([AX_PTHREAD_ZOS_MISSING],
+            [
+#            if !defined(_OPEN_THREADS) && !defined(_UNIX03_THREADS)
+             AX_PTHREAD_ZOS_MISSING
+#            endif
+            ],
+            [AC_MSG_WARN([IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support.])])
+        ;;
+
+        solaris*)
+
+        # On Solaris (at least, for some versions), libc contains stubbed
+        # (non-functional) versions of the pthreads routines, so link-based
+        # tests will erroneously succeed. (N.B.: The stubs are missing
+        # pthread_cleanup_push, or rather a function called by this macro,
+        # so we could check for that, but who knows whether they'll stub
+        # that too in a future libc.)  So we'll check first for the
+        # standard Solaris way of linking pthreads (-mt -lpthread).
+
+        ax_pthread_flags="-mt,-lpthread pthread $ax_pthread_flags"
+        ;;
+esac
+
+# Are we compiling with Clang?
+
+AC_CACHE_CHECK([whether $CC is Clang],
+    [ax_cv_PTHREAD_CLANG],
+    [ax_cv_PTHREAD_CLANG=no
+     # Note that Autoconf sets GCC=yes for Clang as well as GCC
+     if test "x$GCC" = "xyes"; then
+        AC_EGREP_CPP([AX_PTHREAD_CC_IS_CLANG],
+            [/* Note: Clang 2.7 lacks __clang_[a-z]+__ */
+#            if defined(__clang__) && defined(__llvm__)
+             AX_PTHREAD_CC_IS_CLANG
+#            endif
+            ],
+            [ax_cv_PTHREAD_CLANG=yes])
+     fi
+    ])
+ax_pthread_clang="$ax_cv_PTHREAD_CLANG"
+
+
+# GCC generally uses -pthread, or -pthreads on some platforms (e.g. SPARC)
+
+# Note that for GCC and Clang -pthread generally implies -lpthread,
+# except when -nostdlib is passed.
+# This is problematic using libtool to build C++ shared libraries with pthread:
+# [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25460
+# [2] https://bugzilla.redhat.com/show_bug.cgi?id=661333
+# [3] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=468555
+# To solve this, first try -pthread together with -lpthread for GCC
+
+AS_IF([test "x$GCC" = "xyes"],
+      [ax_pthread_flags="-pthread,-lpthread -pthread -pthreads $ax_pthread_flags"])
+
+# Clang takes -pthread (never supported any other flag), but we'll try with -lpthread first
+
+AS_IF([test "x$ax_pthread_clang" = "xyes"],
+      [ax_pthread_flags="-pthread,-lpthread -pthread"])
+
+
+# The presence of a feature test macro requesting re-entrant function
+# definitions is, on some systems, a strong hint that pthreads support is
+# correctly enabled
+
+case $host_os in
+        darwin* | hpux* | linux* | osf* | solaris*)
+        ax_pthread_check_macro="_REENTRANT"
+        ;;
+
+        aix*)
+        ax_pthread_check_macro="_THREAD_SAFE"
+        ;;
+
+        *)
+        ax_pthread_check_macro="--"
+        ;;
+esac
+AS_IF([test "x$ax_pthread_check_macro" = "x--"],
+      [ax_pthread_check_cond=0],
+      [ax_pthread_check_cond="!defined($ax_pthread_check_macro)"])
+
+
+if test "x$ax_pthread_ok" = "xno"; then
+for ax_pthread_try_flag in $ax_pthread_flags; do
+
+        case $ax_pthread_try_flag in
+                none)
+                AC_MSG_CHECKING([whether pthreads work without any flags])
+                ;;
+
+                *,*)
+                PTHREAD_CFLAGS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\1/"`
+                PTHREAD_LIBS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\2/"`
+                AC_MSG_CHECKING([whether pthreads work with "$PTHREAD_CFLAGS" and "$PTHREAD_LIBS"])
+                ;;
+
+                -*)
+                AC_MSG_CHECKING([whether pthreads work with $ax_pthread_try_flag])
+                PTHREAD_CFLAGS="$ax_pthread_try_flag"
+                ;;
+
+                pthread-config)
+                AC_CHECK_PROG([ax_pthread_config], [pthread-config], [yes], [no])
+                AS_IF([test "x$ax_pthread_config" = "xno"], [continue])
+                PTHREAD_CFLAGS="`pthread-config --cflags`"
+                PTHREAD_LIBS="`pthread-config --ldflags` `pthread-config --libs`"
+                ;;
+
+                *)
+                AC_MSG_CHECKING([for the pthreads library -l$ax_pthread_try_flag])
+                PTHREAD_LIBS="-l$ax_pthread_try_flag"
+                ;;
+        esac
+
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Check for various functions.  We must include pthread.h,
+        # since some functions may be macros.  (On the Sequent, we
+        # need a special flag -Kthread to make this header compile.)
+        # We check for pthread_join because it is in -lpthread on IRIX
+        # while pthread_create is in libc.  We check for pthread_attr_init
+        # due to DEC craziness with -lpthreads.  We check for
+        # pthread_cleanup_push because it is one of the few pthread
+        # functions on Solaris that doesn't have a non-functional libc stub.
+        # We try pthread_create on general principles.
+
+        AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <pthread.h>
+#                       if $ax_pthread_check_cond
+#                        error "$ax_pthread_check_macro must be defined"
+#                       endif
+                        static void *some_global = NULL;
+                        static void routine(void *a)
+                          {
+                             /* To avoid any unused-parameter or
+                                unused-but-set-parameter warning.  */
+                             some_global = a;
+                          }
+                        static void *start_routine(void *a) { return a; }],
+                       [pthread_t th; pthread_attr_t attr;
+                        pthread_create(&th, 0, start_routine, 0);
+                        pthread_join(th, 0);
+                        pthread_attr_init(&attr);
+                        pthread_cleanup_push(routine, 0);
+                        pthread_cleanup_pop(0) /* ; */])],
+            [ax_pthread_ok=yes],
+            [])
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        AC_MSG_RESULT([$ax_pthread_ok])
+        AS_IF([test "x$ax_pthread_ok" = "xyes"], [break])
+
+        PTHREAD_LIBS=""
+        PTHREAD_CFLAGS=""
+done
+fi
+
+
+# Clang needs special handling, because older versions handle the -pthread
+# option in a rather... idiosyncratic way
+
+if test "x$ax_pthread_clang" = "xyes"; then
+
+        # Clang takes -pthread; it has never supported any other flag
+
+        # (Note 1: This will need to be revisited if a system that Clang
+        # supports has POSIX threads in a separate library.  This tends not
+        # to be the way of modern systems, but it's conceivable.)
+
+        # (Note 2: On some systems, notably Darwin, -pthread is not needed
+        # to get POSIX threads support; the API is always present and
+        # active.  We could reasonably leave PTHREAD_CFLAGS empty.  But
+        # -pthread does define _REENTRANT, and while the Darwin headers
+        # ignore this macro, third-party headers might not.)
+
+        # However, older versions of Clang make a point of warning the user
+        # that, in an invocation where only linking and no compilation is
+        # taking place, the -pthread option has no effect ("argument unused
+        # during compilation").  They expect -pthread to be passed in only
+        # when source code is being compiled.
+        #
+        # Problem is, this is at odds with the way Automake and most other
+        # C build frameworks function, which is that the same flags used in
+        # compilation (CFLAGS) are also used in linking.  Many systems
+        # supported by AX_PTHREAD require exactly this for POSIX threads
+        # support, and in fact it is often not straightforward to specify a
+        # flag that is used only in the compilation phase and not in
+        # linking.  Such a scenario is extremely rare in practice.
+        #
+        # Even though use of the -pthread flag in linking would only print
+        # a warning, this can be a nuisance for well-run software projects
+        # that build with -Werror.  So if the active version of Clang has
+        # this misfeature, we search for an option to squash it.
+
+        AC_CACHE_CHECK([whether Clang needs flag to prevent "argument unused" warning when linking with -pthread],
+            [ax_cv_PTHREAD_CLANG_NO_WARN_FLAG],
+            [ax_cv_PTHREAD_CLANG_NO_WARN_FLAG=unknown
+             # Create an alternate version of $ac_link that compiles and
+             # links in two steps (.c -> .o, .o -> exe) instead of one
+             # (.c -> exe), because the warning occurs only in the second
+             # step
+             ax_pthread_save_ac_link="$ac_link"
+             ax_pthread_sed='s/conftest\.\$ac_ext/conftest.$ac_objext/g'
+             ax_pthread_link_step=`AS_ECHO(["$ac_link"]) | sed "$ax_pthread_sed"`
+             ax_pthread_2step_ac_link="($ac_compile) && (echo ==== >&5) && ($ax_pthread_link_step)"
+             ax_pthread_save_CFLAGS="$CFLAGS"
+             for ax_pthread_try in '' -Qunused-arguments -Wno-unused-command-line-argument unknown; do
+                AS_IF([test "x$ax_pthread_try" = "xunknown"], [break])
+                CFLAGS="-Werror -Wunknown-warning-option $ax_pthread_try -pthread $ax_pthread_save_CFLAGS"
+                ac_link="$ax_pthread_save_ac_link"
+                AC_LINK_IFELSE([AC_LANG_SOURCE([[int main(void){return 0;}]])],
+                    [ac_link="$ax_pthread_2step_ac_link"
+                     AC_LINK_IFELSE([AC_LANG_SOURCE([[int main(void){return 0;}]])],
+                         [break])
+                    ])
+             done
+             ac_link="$ax_pthread_save_ac_link"
+             CFLAGS="$ax_pthread_save_CFLAGS"
+             AS_IF([test "x$ax_pthread_try" = "x"], [ax_pthread_try=no])
+             ax_cv_PTHREAD_CLANG_NO_WARN_FLAG="$ax_pthread_try"
+            ])
+
+        case "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" in
+                no | unknown) ;;
+                *) PTHREAD_CFLAGS="$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG $PTHREAD_CFLAGS" ;;
+        esac
+
+fi # $ax_pthread_clang = yes
+
+
+
+# Various other checks:
+if test "x$ax_pthread_ok" = "xyes"; then
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Detect AIX lossage: JOINABLE attribute is called UNDETACHED.
+        AC_CACHE_CHECK([for joinable pthread attribute],
+            [ax_cv_PTHREAD_JOINABLE_ATTR],
+            [ax_cv_PTHREAD_JOINABLE_ATTR=unknown
+             for ax_pthread_attr in PTHREAD_CREATE_JOINABLE PTHREAD_CREATE_UNDETACHED; do
+                 AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <pthread.h>],
+                                                 [int attr = $ax_pthread_attr; return attr /* ; */])],
+                                [ax_cv_PTHREAD_JOINABLE_ATTR=$ax_pthread_attr; break],
+                                [])
+             done
+            ])
+        AS_IF([test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xunknown" && \
+               test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xPTHREAD_CREATE_JOINABLE" && \
+               test "x$ax_pthread_joinable_attr_defined" != "xyes"],
+              [AC_DEFINE_UNQUOTED([PTHREAD_CREATE_JOINABLE],
+                                  [$ax_cv_PTHREAD_JOINABLE_ATTR],
+                                  [Define to necessary symbol if this constant
+                                   uses a non-standard name on your system.])
+               ax_pthread_joinable_attr_defined=yes
+              ])
+
+        AC_CACHE_CHECK([whether more special flags are required for pthreads],
+            [ax_cv_PTHREAD_SPECIAL_FLAGS],
+            [ax_cv_PTHREAD_SPECIAL_FLAGS=no
+             case $host_os in
+             solaris*)
+             ax_cv_PTHREAD_SPECIAL_FLAGS="-D_POSIX_PTHREAD_SEMANTICS"
+             ;;
+             esac
+            ])
+        AS_IF([test "x$ax_cv_PTHREAD_SPECIAL_FLAGS" != "xno" && \
+               test "x$ax_pthread_special_flags_added" != "xyes"],
+              [PTHREAD_CFLAGS="$ax_cv_PTHREAD_SPECIAL_FLAGS $PTHREAD_CFLAGS"
+               ax_pthread_special_flags_added=yes])
+
+        AC_CACHE_CHECK([for PTHREAD_PRIO_INHERIT],
+            [ax_cv_PTHREAD_PRIO_INHERIT],
+            [AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <pthread.h>]],
+                                             [[int i = PTHREAD_PRIO_INHERIT;
+                                               return i;]])],
+                            [ax_cv_PTHREAD_PRIO_INHERIT=yes],
+                            [ax_cv_PTHREAD_PRIO_INHERIT=no])
+            ])
+        AS_IF([test "x$ax_cv_PTHREAD_PRIO_INHERIT" = "xyes" && \
+               test "x$ax_pthread_prio_inherit_defined" != "xyes"],
+              [AC_DEFINE([HAVE_PTHREAD_PRIO_INHERIT], [1], [Have PTHREAD_PRIO_INHERIT.])
+               ax_pthread_prio_inherit_defined=yes
+              ])
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        # More AIX lossage: compile with *_r variant
+        if test "x$GCC" != "xyes"; then
+            case $host_os in
+                aix*)
+                AS_CASE(["x/$CC"],
+                    [x*/c89|x*/c89_128|x*/c99|x*/c99_128|x*/cc|x*/cc128|x*/xlc|x*/xlc_v6|x*/xlc128|x*/xlc128_v6],
+                    [#handle absolute path differently from PATH based program lookup
+                     AS_CASE(["x$CC"],
+                         [x/*],
+                         [
+			   AS_IF([AS_EXECUTABLE_P([${CC}_r])],[PTHREAD_CC="${CC}_r"])
+			   AS_IF([test "x${CXX}" != "x"], [AS_IF([AS_EXECUTABLE_P([${CXX}_r])],[PTHREAD_CXX="${CXX}_r"])])
+			 ],
+                         [
+			   AC_CHECK_PROGS([PTHREAD_CC],[${CC}_r],[$CC])
+			   AS_IF([test "x${CXX}" != "x"], [AC_CHECK_PROGS([PTHREAD_CXX],[${CXX}_r],[$CXX])])
+			 ]
+                     )
+                    ])
+                ;;
+            esac
+        fi
+fi
+
+test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+test -n "$PTHREAD_CXX" || PTHREAD_CXX="$CXX"
+
+AC_SUBST([PTHREAD_LIBS])
+AC_SUBST([PTHREAD_CFLAGS])
+AC_SUBST([PTHREAD_CC])
+AC_SUBST([PTHREAD_CXX])
+
+# Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND:
+if test "x$ax_pthread_ok" = "xyes"; then
+        ifelse([$1],,[AC_DEFINE([HAVE_PTHREAD],[1],[Define if you have POSIX threads libraries and header files.])],[$1])
+        :
+else
+        ax_pthread_ok=no
+        $2
+fi
+AC_LANG_POP
+])dnl AX_PTHREAD
diff --git a/tests/Makefile.am b/tests/Makefile.am
index a7b6851..e2e661b 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -17,7 +17,8 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-TESTSUITE_FRAGMENTS = api-21.at api-24.at tls-alignment.at elf-cleaner.at
+TESTSUITE_FRAGMENTS = api-21.at api-24.at tls-alignment.at	\
+elf-cleaner.at threads.at
 
 EXTRA_DIST = $(TESTSUITE_AT) testsuite package.m4
 
diff --git a/tests/elf-cleaner.at b/tests/elf-cleaner.at
index 70d59f6..fb1b140 100644
--- a/tests/elf-cleaner.at
+++ b/tests/elf-cleaner.at
@@ -29,3 +29,5 @@ m4_include([api-21.at])
 m4_include([api-24.at])
 
 m4_include([tls-alignment.at])
+
+m4_include([threads.at])
diff --git a/tests/threads.at b/tests/threads.at
new file mode 100644
index 0000000..18a8955
--- /dev/null
+++ b/tests/threads.at
@@ -0,0 +1,39 @@
+# Process this file with autom4te to create testsuite. -*- Autotest -*-
+
+# Test suite for termux-elf-cleaner.
+# Copyright 2022 Termux
+
+# This file is part of termux-elf-cleaner.
+
+# termux-elf-cleaner is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation; either version 3 of the
+# License, or (at your option) any later version.
+
+# termux-elf-cleaner 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
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see
+# <http://www.gnu.org/licenses/>.
+
+# Ensure that termux-elf-cleaner can run on several threads
+
+AT_BANNER([Multiple threads])
+
+AT_SETUP([Parallel on 100 files])
+AT_KEYWORDS([dynamic-section api-24 aarch64])
+AT_CHECK([
+for i in $(seq 1 100); do
+  cp ${top_srcdir}/tests/curl-7.83.1-aarch64-original curl-7.83.1-aarch64-original-$i
+done
+${abs_top_builddir}/termux-elf-cleaner --api-level 24 --jobs 4 --quiet curl-7.83.1-aarch64-original-*
+for i in $(seq 1 100); do
+  cmp --silent curl-7.83.1-aarch64-original-$i ${top_srcdir}/tests/curl-7.83.1-aarch64-api24-cleaned
+done
+],
+[0],
+[])
+AT_CLEANUP