nptl: Remove MULTI_PAGE_ALIASING [BZ #23554]

MULTI_PAGE_ALIASING was introduced to mitigate an aliasing issue on
Pentium 4.  It is no longer needed for processors after Pentium 4.

diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 149b999603e2a6bd54c168f17b2049f6e9d86b73..00fddbd409e0aa81b0f234835e4b43e546319e1d 100644 (file)
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -31,7 +31,6 @@
 #include <lowlevellock.h>
 #include <futex-internal.h>
 #include <kernel-features.h>
-#include <stack-aliasing.h>
 
 
 #ifndef NEED_SEPARATE_REGISTER_STACK
@@ -547,15 +546,6 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
       pd = get_cached_stack (&size, &mem);
       if (pd == NULL)
        {
-         /* To avoid aliasing effects on a larger scale than pages we
-            adjust the allocated stack size if necessary.  This way
-            allocations directly following each other will not have
-            aliasing problems.  */
-#if MULTI_PAGE_ALIASING != 0
-         if ((size % MULTI_PAGE_ALIASING) == 0)
-           size += pagesize_m1 + 1;
-#endif
-
          /* If a guard page is required, avoid committing memory by first
             allocate with PROT_NONE and then reserve with required permission
             excluding the guard page.  */

diff --git a/nptl/stack-aliasing.h b/nptl/stack-aliasing.h
deleted file mode 100644 (file)
index bfdde53..0000000
--- a/nptl/stack-aliasing.h
+++ /dev/null
@@ -1,23 +0,0 @@
-/* Define macros for stack address aliasing issues for NPTL.  Stub version.
-   Copyright (C) 2014-2021 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
-   <https://www.gnu.org/licenses/>.  */
-
-/* This is a number of bytes that is an alignment that should be avoided
-   when choosing the exact size of a new thread's stack.  If the size
-   chosen is aligned to this, an extra page will be added to render the
-   size off-aligned.  */
-#define MULTI_PAGE_ALIASING     0

diff --git a/sysdeps/i386/i686/stack-aliasing.h b/sysdeps/i386/i686/stack-aliasing.h
deleted file mode 100644 (file)
index d521dcd..0000000
--- a/sysdeps/i386/i686/stack-aliasing.h
+++ /dev/null
@@ -1,23 +0,0 @@
-/* Define macros for stack address aliasing issues for NPTL.  i686 version.
-   Copyright (C) 2014-2021 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
-   <https://www.gnu.org/licenses/>.  */
-
-/* What is useful is to avoid the 64k aliasing problem which reliably
-   happens if all stacks use sizes which are a multiple of 64k.  Tell
-   the stack allocator to disturb this by allocation one more page if
-   necessary.  */
-#define MULTI_PAGE_ALIASING     65536

diff --git a/sysdeps/x86_64/stack-aliasing.h b/sysdeps/x86_64/stack-aliasing.h
deleted file mode 100644 (file)
index 2efdacb..0000000
--- a/sysdeps/x86_64/stack-aliasing.h
+++ /dev/null
@@ -1 +0,0 @@
-#include <sysdeps/i386/i686/stack-aliasing.h>