diff --git a/stdlib/Makefile b/stdlib/Makefile
index 095518eef4..6af606136e 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -214,6 +214,7 @@ tests := \
   tst-on_exit \
   tst-qsort \
   tst-qsort2 \
+  tst-qsort3 \
   tst-quick_exit \
   tst-rand48 \
   tst-rand48-2 \
diff --git a/stdlib/tst-qsort3.c b/stdlib/tst-qsort3.c
new file mode 100644
index 0000000000..421560d744
--- /dev/null
+++ b/stdlib/tst-qsort3.c
@@ -0,0 +1,366 @@
+/* qsort(_r) tests to trigger worst case for quicksort.
+   Copyright (C) 2023 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 <array_length.h>
+#include <errno.h>
+#include <getopt.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/test-driver.h>
+
+typedef enum
+{
+  Sorted,
+  Random,
+  Repeated,
+  Bitonic,
+  Duplicated,
+} arraytype_t;
+
+/* Ratio of total of elements which will be repeated.  */
+static const double RepeatedRatio = 0.2;
+
+/* Ratio of duplicated element .  */
+static const double DuplicatedRatio = 0.4;
+
+struct array_t
+{
+  arraytype_t type;
+  const char *name;
+} static const arraytypes[] =
+{
+  { Sorted,       "Sorted" },
+  { Random,       "Random" },
+  { Repeated,     "Repeated" },
+  { Bitonic,      "Bitonic" },
+  { Duplicated,   "Duplicated" },
+};
+
+/* Return the index of BASE as interpreted as an array of elements
+   of size SIZE.  */
+static inline void *
+arr (void *base, size_t idx, size_t size)
+{
+  return (void*)((uintptr_t)base + (idx * size));
+}
+
+/* Functions used to check qsort.  */
+static int
+uint8_t_cmp (const void *a, const void *b)
+{
+  uint8_t ia = *(uint8_t*)a;
+  uint8_t ib = *(uint8_t*)b;
+  return (ia > ib) - (ia < ib);
+}
+
+static int
+uint16_t_cmp (const void *a, const void *b)
+{
+  uint16_t ia = *(uint16_t*)a;
+  uint16_t ib = *(uint16_t*)b;
+  return (ia > ib) - (ia < ib);
+}
+
+static int
+uint32_t_cmp (const void *a, const void *b)
+{
+  uint32_t ia = *(uint32_t*)a;
+  uint32_t ib = *(uint32_t*)b;
+  return (ia > ib) - (ia < ib);
+}
+
+static int
+uint64_t_cmp (const void *a, const void *b)
+{
+  uint64_t ia = *(uint64_t*)a;
+  uint64_t ib = *(uint64_t*)b;
+  return (ia > ib) - (ia < ib);
+}
+
+#define LARGE_SIZE 47
+
+static int
+large_cmp (const void *a, const void *b)
+{
+  return memcmp (a, b, LARGE_SIZE);
+}
+
+/* Function used to check qsort_r.  */
+typedef enum
+{
+  UINT8_CMP_T,
+  UINT16_CMP_T,
+  UINT32_CMP_T,
+  UINT64_CMP_T,
+  LARGE_CMP_T
+} type_cmp_t;
+
+static type_cmp_t
+uint_t_cmp_type (size_t sz)
+{
+  switch (sz)
+    {
+      case sizeof (uint8_t):  return UINT8_CMP_T;
+      case sizeof (uint16_t): return UINT16_CMP_T;
+      case sizeof (uint64_t): return UINT64_CMP_T;
+      case sizeof (uint32_t): return UINT32_CMP_T;
+      default:                return LARGE_CMP_T;
+    }
+}
+
+static int
+uint_t_cmp (const void *a, const void *b, void *arg)
+{
+  type_cmp_t type = *(type_cmp_t*) arg;
+  switch (type)
+    {
+    case UINT8_CMP_T:  return uint8_t_cmp (a, b);
+    case UINT32_CMP_T: return uint32_t_cmp (a, b);
+    case UINT16_CMP_T: return uint16_t_cmp (a, b);
+    case UINT64_CMP_T: return uint64_t_cmp (a, b);
+    default:           return large_cmp (a, b);
+    }
+}
+
+static void
+seq (void *elem, size_t type_size, int value)
+{
+  if (type_size == sizeof (uint8_t))
+    *(uint8_t*)elem = value;
+  else if (type_size == sizeof (uint16_t))
+    *(uint16_t*)elem = value;
+  else if (type_size == sizeof (uint32_t))
+    *(uint32_t*)elem = value;
+  else if (type_size == sizeof (uint64_t))
+    *(uint64_t*)elem = value;
+  else
+    memset (elem, value, type_size);
+}
+
+static void
+fill_array (void *array, void *refarray, size_t nmemb, size_t type_size,
+	    arraytype_t type)
+{
+  size_t size = nmemb * type_size;
+
+  switch (type)
+    {
+    case Sorted:
+      for (size_t i = 0; i < nmemb; i++)
+	seq (arr (array, i, type_size), type_size, i);
+      break;
+
+    case Random:
+      arc4random_buf (array, size);
+      break;
+
+    case Repeated:
+      {
+        arc4random_buf (array, size);
+
+	void *randelem = xmalloc (type_size);
+	arc4random_buf (randelem, type_size);
+
+	/* Repeat REPEATED elements (based on RepeatRatio ratio) in the random
+	   array.  */
+        size_t repeated = (size_t)(nmemb * RepeatedRatio);
+	for (size_t i = 0; i < repeated; i++)
+	  {
+	    size_t pos = arc4random_uniform (nmemb - 1);
+	    memcpy (arr (array, pos, type_size), randelem, type_size);
+	  }
+	free (randelem);
+      }
+      break;
+
+    case Bitonic:
+      {
+	size_t i;
+        for (i = 0; i < nmemb / 2; i++)
+	  seq (arr (array, i, type_size), type_size, i);
+        for (     ; i < nmemb;     i++)
+	  seq (arr (array, i, type_size), type_size, (nmemb - 1) - i);
+      }
+      break;
+
+    case Duplicated:
+      {
+	int randelem1 = arc4random ();
+	for (size_t i = 0; i < nmemb; i++)
+	  seq (arr (array, i, type_size), type_size, randelem1);
+
+	size_t duplicates = (size_t)(nmemb * DuplicatedRatio);
+	int randelem2 = arc4random ();
+	for (size_t i = 0; i < duplicates; i++)
+	  {
+	    size_t pos = arc4random_uniform (nmemb - 1);
+	    seq (arr (array, pos, type_size), type_size, randelem2);
+	  }
+      }
+      break;
+    }
+
+  memcpy (refarray, array, size);
+}
+
+typedef int (*cmpfunc_t)(const void *, const void *);
+
+/* Simple insertion sort to use as reference sort.  */
+static void
+qsort_r_ref (void *p, size_t n, size_t s, __compar_d_fn_t cmp, void *arg)
+{
+  if (n <= 1)
+    return;
+
+  int i = 1;
+  char tmp[s];
+  while (i < n)
+    {
+      memcpy (tmp, arr (p, i, s), s);
+      int j = i - 1;
+      while (j >= 0 && cmp (arr (p, j, s), tmp, arg) > 0)
+	{
+	  memcpy (arr (p, j + 1, s), arr (p, j, s), s);
+	  j = j - 1;
+	}
+      memcpy (arr (p, j + 1, s), tmp, s);
+      i = i + 1;
+    }
+}
+
+static void
+qsort_ref (void *b, size_t n, size_t s, __compar_fn_t cmp)
+{
+  return qsort_r_ref (b, n, s, (__compar_d_fn_t) cmp, NULL);
+}
+
+/* Check if ARRAY of total NMEMB element of size SIZE is sorted
+   based on CMPFUNC.  */
+static void
+check_array (void *array, void *refarray, size_t nmemb, size_t type_size,
+	     cmpfunc_t cmpfunc)
+{
+  for (size_t i = 1; i < nmemb; i++)
+    {
+      int ret = cmpfunc (arr (array, i,   type_size),
+			 arr (array, i-1, type_size));
+      TEST_VERIFY_EXIT (ret >= 0);
+    }
+
+  size_t size = nmemb * type_size;
+  TEST_COMPARE_BLOB (array, size, refarray, size);
+}
+
+static void
+check_qsort (void *buf, void *refbuf, size_t nelem, size_t type_size,
+	     arraytype_t type, cmpfunc_t cmpfunc)
+{
+  fill_array (buf, refbuf, nelem, type_size, type);
+
+  qsort (buf, nelem, type_size, cmpfunc);
+  qsort_ref (refbuf, nelem, type_size, cmpfunc);
+
+  check_array (buf, refbuf, nelem, type_size, cmpfunc);
+}
+
+static void
+check_qsort_r (void *buf, void *refbuf, size_t nelem, size_t type_size,
+	       arraytype_t type, cmpfunc_t cmpfunc)
+{
+  fill_array (buf, refbuf, nelem, type_size, type);
+
+  type_cmp_t typecmp = uint_t_cmp_type (type_size);
+
+  qsort_r (buf, nelem, type_size, uint_t_cmp, &typecmp);
+  qsort_r_ref (refbuf, nelem, type_size, uint_t_cmp, &typecmp);
+
+  check_array (buf, refbuf, nelem, type_size, cmpfunc);
+}
+
+static int
+do_test (void)
+{
+  /* Some random sizes.  */
+  static const size_t nelems[] = { 0, 1, 7, 20, 32, 100, 256, 1024, 4256 };
+  size_t max_nelems = 0;
+  for (int i = 0; i < array_length (nelems); i++)
+    if (nelems[i] > max_nelems)
+      max_nelems = nelems[i];
+
+  static const struct test_t
+    {
+      size_t type_size;
+      cmpfunc_t cmpfunc;
+    }
+  tests[] =
+    {
+      { sizeof (uint8_t),  uint8_t_cmp },
+      { sizeof (uint16_t), uint16_t_cmp },
+      { sizeof (uint32_t), uint32_t_cmp },
+      { sizeof (uint64_t), uint64_t_cmp },
+      /* Test swap with large elements.  */
+      { LARGE_SIZE,        large_cmp },
+    };
+  size_t max_type_size = 0;
+  for (int i = 0; i < array_length (tests); i++)
+    if (tests[i].type_size > max_type_size)
+      max_type_size = tests[i].type_size;
+
+  void *buf = reallocarray (NULL, max_nelems, max_type_size);
+  TEST_VERIFY_EXIT (buf != NULL);
+  void *refbuf = reallocarray (NULL, max_nelems, max_type_size);
+  TEST_VERIFY_EXIT (refbuf != NULL);
+
+  for (const struct test_t *test = tests; test < array_end (tests); ++test)
+    {
+      if (test_verbose > 0)
+	printf ("info: testing qsort with type_size=%zu\n", test->type_size);
+      for (const struct array_t *arraytype = arraytypes;
+	   arraytype < array_end (arraytypes);
+	   ++arraytype)
+	{
+	  if (test_verbose > 0)
+            printf ("  distribution=%s\n", arraytype->name);
+	  for (const size_t *nelem = nelems;
+	       nelem < array_end (nelems);
+	       ++nelem)
+	    {
+	      if (test_verbose > 0)
+		printf ("    nelem=%zu, total size=%zu\n", *nelem,
+			*nelem * test->type_size);
+
+	      check_qsort (buf, refbuf, *nelem, test->type_size,
+			   arraytype->type, test->cmpfunc);
+	      check_qsort_r (buf, refbuf, *nelem, test->type_size,
+			     arraytype->type, test->cmpfunc);
+	   }
+	}
+    }
+
+  free (buf);
+  free (refbuf);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
