--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/os_cpu/linux_x86/vm/threadLS_linux_x86.cpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,91 @@
+/*
+ * Copyright 1999-2003 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code 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
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+#include "incls/_precompiled.incl"
+#include "incls/_threadLS_linux_x86.cpp.incl"
+
+// Map stack pointer (%esp) to thread pointer for faster TLS access
+//
+// Here we use a flat table for better performance. Getting current thread
+// is down to one memory access (read _sp_map[%esp>>12]) in generated code
+// and two in runtime code (-fPIC code needs an extra load for _sp_map).
+//
+// This code assumes stack page is not shared by different threads. It works
+// in 32-bit VM when page size is 4K (or a multiple of 4K, if that matters).
+//
+// Notice that _sp_map is allocated in the bss segment, which is ZFOD
+// (zero-fill-on-demand). While it reserves 4M address space upfront,
+// actual memory pages are committed on demand.
+//
+// If an application creates and destroys a lot of threads, usually the
+// stack space freed by a thread will soon get reused by new thread
+// (this is especially true in NPTL or LinuxThreads in fixed-stack mode).
+// No memory page in _sp_map is wasted.
+//
+// However, it's still possible that we might end up populating &
+// committing a large fraction of the 4M table over time, but the actual
+// amount of live data in the table could be quite small. The max wastage
+// is less than 4M bytes. If it becomes an issue, we could use madvise()
+// with MADV_DONTNEED to reclaim unused (i.e. all-zero) pages in _sp_map.
+// MADV_DONTNEED on Linux keeps the virtual memory mapping, but zaps the
+// physical memory page (i.e. similar to MADV_FREE on Solaris).
+
+#ifndef AMD64
+Thread* ThreadLocalStorage::_sp_map[1UL << (SP_BITLENGTH - PAGE_SHIFT)];
+#endif // !AMD64
+
+void ThreadLocalStorage::generate_code_for_get_thread() {
+    // nothing we can do here for user-level thread
+}
+
+void ThreadLocalStorage::pd_init() {
+#ifndef AMD64
+  assert(align_size_down(os::vm_page_size(), PAGE_SIZE) == os::vm_page_size(),
+         "page size must be multiple of PAGE_SIZE");
+#endif // !AMD64
+}
+
+void ThreadLocalStorage::pd_set_thread(Thread* thread) {
+  os::thread_local_storage_at_put(ThreadLocalStorage::thread_index(), thread);
+
+#ifndef AMD64
+  address stack_top = os::current_stack_base();
+  size_t stack_size = os::current_stack_size();
+
+  for (address p = stack_top - stack_size; p < stack_top; p += PAGE_SIZE) {
+    // pd_set_thread() is called with non-NULL value when a new thread is
+    // created/attached, or with NULL value when a thread is about to exit.
+    // If both "thread" and the corresponding _sp_map[] entry are non-NULL,
+    // they should have the same value. Otherwise it might indicate that the
+    // stack page is shared by multiple threads. However, a more likely cause
+    // for this assertion to fail is that an attached thread exited without
+    // detaching itself from VM, which is a program error and could cause VM
+    // to crash.
+    assert(thread == NULL || _sp_map[(uintptr_t)p >> PAGE_SHIFT] == NULL ||
+           thread == _sp_map[(uintptr_t)p >> PAGE_SHIFT],
+           "thread exited without detaching from VM??");
+    _sp_map[(uintptr_t)p >> PAGE_SHIFT] = thread;
+  }
+#endif // !AMD64
+}