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src/os_cpu/linux_x86/vm/threadLS_linux_x86.cpp@f03d0a26bf83 (annotated)

src/os_cpu/linux_x86/vm/threadLS_linux_x86.cpp

Thu, 22 Apr 2010 13:23:15 -0700

author

jcoomes

date

Thu, 22 Apr 2010 13:23:15 -0700

changeset 1845

f03d0a26bf83

parent 435

a61af66fc99e

child 1907

c18cbe5936b8

permissions

-rw-r--r--

6888954: argument formatting for assert() and friends
Reviewed-by: kvn, twisti, apetrusenko, never, dcubed

duke@435	1	/*
duke@435	2	* Copyright 1999-2003 Sun Microsystems, Inc. All Rights Reserved.
duke@435	3	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435	4	*
duke@435	5	* This code is free software; you can redistribute it and/or modify it
duke@435	6	* under the terms of the GNU General Public License version 2 only, as
duke@435	7	* published by the Free Software Foundation.
duke@435	8	*
duke@435	9	* This code is distributed in the hope that it will be useful, but WITHOUT
duke@435	10	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435	11	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
duke@435	12	* version 2 for more details (a copy is included in the LICENSE file that
duke@435	13	* accompanied this code).
duke@435	14	*
duke@435	15	* You should have received a copy of the GNU General Public License version
duke@435	16	* 2 along with this work; if not, write to the Free Software Foundation,
duke@435	17	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435	18	*
duke@435	19	* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@435	20	* CA 95054 USA or visit www.sun.com if you need additional information or
duke@435	21	* have any questions.
duke@435	22	*
duke@435	23	*/
duke@435	24
duke@435	25	#include "incls/_precompiled.incl"
duke@435	26	#include "incls/_threadLS_linux_x86.cpp.incl"
duke@435	27
duke@435	28	// Map stack pointer (%esp) to thread pointer for faster TLS access
duke@435	29	//
duke@435	30	// Here we use a flat table for better performance. Getting current thread
duke@435	31	// is down to one memory access (read _sp_map[%esp>>12]) in generated code
duke@435	32	// and two in runtime code (-fPIC code needs an extra load for _sp_map).
duke@435	33	//
duke@435	34	// This code assumes stack page is not shared by different threads. It works
duke@435	35	// in 32-bit VM when page size is 4K (or a multiple of 4K, if that matters).
duke@435	36	//
duke@435	37	// Notice that _sp_map is allocated in the bss segment, which is ZFOD
duke@435	38	// (zero-fill-on-demand). While it reserves 4M address space upfront,
duke@435	39	// actual memory pages are committed on demand.
duke@435	40	//
duke@435	41	// If an application creates and destroys a lot of threads, usually the
duke@435	42	// stack space freed by a thread will soon get reused by new thread
duke@435	43	// (this is especially true in NPTL or LinuxThreads in fixed-stack mode).
duke@435	44	// No memory page in _sp_map is wasted.
duke@435	45	//
duke@435	46	// However, it's still possible that we might end up populating &
duke@435	47	// committing a large fraction of the 4M table over time, but the actual
duke@435	48	// amount of live data in the table could be quite small. The max wastage
duke@435	49	// is less than 4M bytes. If it becomes an issue, we could use madvise()
duke@435	50	// with MADV_DONTNEED to reclaim unused (i.e. all-zero) pages in _sp_map.
duke@435	51	// MADV_DONTNEED on Linux keeps the virtual memory mapping, but zaps the
duke@435	52	// physical memory page (i.e. similar to MADV_FREE on Solaris).
duke@435	53
duke@435	54	#ifndef AMD64
duke@435	55	Thread* ThreadLocalStorage::_sp_map[1UL << (SP_BITLENGTH - PAGE_SHIFT)];
duke@435	56	#endif // !AMD64
duke@435	57
duke@435	58	void ThreadLocalStorage::generate_code_for_get_thread() {
duke@435	59	// nothing we can do here for user-level thread
duke@435	60	}
duke@435	61
duke@435	62	void ThreadLocalStorage::pd_init() {
duke@435	63	#ifndef AMD64
duke@435	64	assert(align_size_down(os::vm_page_size(), PAGE_SIZE) == os::vm_page_size(),
duke@435	65	"page size must be multiple of PAGE_SIZE");
duke@435	66	#endif // !AMD64
duke@435	67	}
duke@435	68
duke@435	69	void ThreadLocalStorage::pd_set_thread(Thread* thread) {
duke@435	70	os::thread_local_storage_at_put(ThreadLocalStorage::thread_index(), thread);
duke@435	71
duke@435	72	#ifndef AMD64
duke@435	73	address stack_top = os::current_stack_base();
duke@435	74	size_t stack_size = os::current_stack_size();
duke@435	75
duke@435	76	for (address p = stack_top - stack_size; p < stack_top; p += PAGE_SIZE) {
duke@435	77	// pd_set_thread() is called with non-NULL value when a new thread is
duke@435	78	// created/attached, or with NULL value when a thread is about to exit.
duke@435	79	// If both "thread" and the corresponding _sp_map[] entry are non-NULL,
duke@435	80	// they should have the same value. Otherwise it might indicate that the
duke@435	81	// stack page is shared by multiple threads. However, a more likely cause
duke@435	82	// for this assertion to fail is that an attached thread exited without
duke@435	83	// detaching itself from VM, which is a program error and could cause VM
duke@435	84	// to crash.
duke@435	85	assert(thread == NULL || _sp_map[(uintptr_t)p >> PAGE_SHIFT] == NULL ||
duke@435	86	thread == _sp_map[(uintptr_t)p >> PAGE_SHIFT],
duke@435	87	"thread exited without detaching from VM??");
duke@435	88	_sp_map[(uintptr_t)p >> PAGE_SHIFT] = thread;
duke@435	89	}
duke@435	90	#endif // !AMD64
duke@435	91	}