530 lines
15 KiB
C
530 lines
15 KiB
C
/* Copyright (C) 2002 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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#include <assert.h>
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#include <errno.h>
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#include <stdint.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/mman.h>
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#include <sys/param.h>
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#include <dl-sysdep.h>
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#include <tls.h>
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/* Most architectures have exactly one stack pointer. Some have more. */
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#define STACK_VARIABLES void *stackaddr
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/* How to pass the values to the 'create_thread' function. */
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#define STACK_VARIABLES_ARGS stackaddr
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/* How to declare function which gets there parameters. */
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#define STACK_VARIABLES_PARMS void *stackaddr
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/* Default alignment of stack. */
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#ifndef STACK_ALIGN
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# define STACK_ALIGN __alignof__ (long double)
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#endif
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/* Default value for minimal stack size after allocating thread
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descriptor and guard. */
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#ifndef MINIMAL_REST_STACK
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# define MINIMAL_REST_STACK 4096
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#endif
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/* Cache handling for not-yet free stacks. */
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/* Maximum size in kB of cache. */
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static size_t stack_cache_maxsize = 40 * 1024 * 1024; /* 40MiBi by default. */
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static size_t stack_cache_actsize;
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/* Mutex protecting this variable. */
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static lll_lock_t stack_cache_lock = LLL_LOCK_INITIALIZER;
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/* List of queued stack frames. */
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static LIST_HEAD (stack_cache);
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/* List of the stacks in use. */
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static LIST_HEAD (stack_used);
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/* List of the threads with user provided stacks in use. No need to
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initialize this, since it's done in __pthread_initialize_minimal. */
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list_t __stack_user __attribute__ ((nocommon));
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hidden_def (__stack_user)
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/* Number of threads running. */
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static unsigned int nptl_nthreads = 1;
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/* Check whether the stack is still used or not. */
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#define FREE_P(descr) ((descr)->tid == 0)
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/* We create a double linked list of all cache entries. Double linked
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because this allows removing entries from the end. */
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/* Get a stack frame from the cache. We have to match by size since
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some blocks might be too small or far too large. */
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static struct pthread *
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get_cached_stack (size_t *sizep, void **memp)
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{
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size_t size = *sizep;
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struct pthread *result = NULL;
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list_t *entry;
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lll_lock (stack_cache_lock);
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/* Search the cache for a matching entry. We search for the
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smallest stack which has at least the required size. Note that
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in normal situations the size of all allocated stacks is the
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same. As the very least there are only a few different sizes.
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Therefore this loop will exit early most of the time with an
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exact match. */
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list_for_each (entry, &stack_cache)
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{
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struct pthread *curr;
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curr = list_entry (entry, struct pthread, header.data.list);
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if (FREE_P (curr) && curr->stackblock_size >= size)
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{
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if (curr->stackblock_size == size)
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{
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result = curr;
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break;
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}
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if (result == NULL
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|| result->stackblock_size > curr->stackblock_size)
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result = curr;
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}
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}
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if (__builtin_expect (result == NULL, 0)
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/* Make sure the size difference is not too excessive. In that
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case we do not use the block. */
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|| __builtin_expect (result->stackblock_size > 4 * size, 0))
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{
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/* Release the lock. */
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lll_unlock (stack_cache_lock);
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return NULL;
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}
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/* Dequeue the entry. */
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list_del (&result->header.data.list);
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/* And add to the list of stacks in use. */
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list_add (&result->header.data.list, &stack_used);
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/* One more thread. */
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++nptl_nthreads;
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/* And decrease the cache size. */
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stack_cache_actsize -= result->stackblock_size;
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/* Release the lock early. */
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lll_unlock (stack_cache_lock);
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*sizep = result->stackblock_size;
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*memp = result->stackblock;
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/* Cancellation handling is back to the default. */
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result->cancelhandling = 0;
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result->cleanup = NULL;
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/* No pending event. */
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result->nextevent = NULL;
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/* Clear the DTV. */
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dtv_t *dtv = GET_DTV (result);
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memset (dtv, '\0', (dtv[-1].counter + 1) * sizeof (dtv_t));
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/* Re-initialize the TLS. */
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return _dl_allocate_tls_init (result);
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}
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/* Add a stack frame which is not used anymore to the stack. Must be
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called with the cache lock held. */
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static void
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queue_stack (struct pthread *stack)
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{
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/* We unconditionally add the stack to the list. The memory may
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still be in use but it will not be reused until the kernel marks
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the stack as not used anymore. */
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list_add (&stack->header.data.list, &stack_cache);
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stack_cache_actsize += stack->stackblock_size;
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if (__builtin_expect (stack_cache_actsize > stack_cache_maxsize, 0))
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{
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/* We reduce the size of the cache. Remove the last entries
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until the size is below the limit. */
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list_t *entry;
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list_t *prev;
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/* Search from the end of the list. */
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list_for_each_prev_safe (entry, prev, &stack_cache)
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{
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struct pthread *curr;
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curr = list_entry(entry, struct pthread, header.data.list);
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if (FREE_P (curr))
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{
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/* Unlink the block. */
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list_del (entry);
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/* Account for the freed memory. */
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stack_cache_actsize -= curr->stackblock_size;
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/* Free the memory associated with the ELF TLS. */
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_dl_deallocate_tls (curr, false);
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/* Remove this block. This should never fail. If it
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does something is really wrong. */
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if (munmap (curr->stackblock, curr->stackblock_size) != 0)
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abort ();
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/* Maybe we have freed enough. */
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if (stack_cache_actsize <= stack_cache_maxsize)
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break;
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}
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}
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}
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}
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static int
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allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
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void **stack)
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{
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struct pthread *pd;
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size_t size;
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size_t pagesize = __sysconf (_SC_PAGESIZE);
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assert (attr != NULL);
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assert (powerof2 (pagesize));
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assert (TCB_ALIGNMENT >= STACK_ALIGN);
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/* Get the stack size from the attribute if it is set. Otherwise we
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use the default we determined at start time. */
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size = attr->stacksize ?: __default_stacksize;
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/* Get memory for the stack. */
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if (__builtin_expect (attr->flags & ATTR_FLAG_STACKADDR, 0))
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{
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uintptr_t adj;
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/* If the user also specified the size of the stack make sure it
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is large enough. */
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if (attr->stacksize != 0
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&& attr->stacksize < (__static_tls_size + MINIMAL_REST_STACK))
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return EINVAL;
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/* Adjust stack size for alignment of the TLS block. */
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adj = ((uintptr_t) attr->stackaddr) & (__static_tls_align - 1);
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assert (size > adj);
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/* The user provided some memory. Let's hope it matches the
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size... We do not allocate guard pages if the user provided
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the stack. It is the user's responsibility to do this if it
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is wanted. */
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pd = (struct pthread *) (((uintptr_t) attr->stackaddr - adj)
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& ~(__alignof (struct pthread) - 1)) - 1;
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/* The user provided stack memory need not be cleared. */
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memset (pd, '\0', sizeof (struct pthread));
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/* The first TSD block is included in the TCB. */
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pd->specific[0] = pd->specific_1stblock;
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/* Initialize the lock. */
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pd->lock = LLL_LOCK_INITIALIZER;
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/* Remember the stack-related values. Signal that this stack
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must not be put into the stack cache. */
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pd->stackblock = (char *) attr->stackaddr - size;
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pd->stackblock_size = size - adj;
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/* This is a user-provided stack. */
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pd->user_stack = true;
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/* There is at least one more thread. */
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pd->header.data.multiple_threads = 1;
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#ifdef NEED_DL_SYSINFO
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/* Copy the sysinfo value from the parent. */
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pd->header.data.sysinfo
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= THREAD_GETMEM (THREAD_SELF, header.data.sysinfo);
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#endif
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/* Allocate the DTV for this thread. */
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if (_dl_allocate_tls (pd) == NULL)
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/* Something went wrong. */
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return errno;
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lll_lock (stack_cache_lock);
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/* And add to the list of stacks in use. */
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list_add (&pd->header.data.list, &__stack_user);
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/* One more thread. */
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++nptl_nthreads;
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lll_unlock (stack_cache_lock);
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}
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else
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{
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/* Allocate some anonymous memory. If possible use the
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cache. */
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size_t guardsize;
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size_t reqsize;
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void *mem;
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/* Adjust the stack size for alignment. */
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size &= ~(__static_tls_align - 1);
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assert (size != 0);
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/* Make sure the size of the stack is enough for the guard and
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eventually the thread descriptor. */
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guardsize = (attr->guardsize + pagesize - 1) & ~(pagesize - 1);
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if (__builtin_expect (size < (guardsize + __static_tls_size
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+ MINIMAL_REST_STACK), 0))
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/* The stack is too small (or the guard too large). */
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return EINVAL;
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reqsize = size;
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pd = get_cached_stack (&size, &mem);
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if (pd == NULL)
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{
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mem = mmap (NULL, size, PROT_READ | PROT_WRITE | PROT_EXEC,
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MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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if (__builtin_expect (mem == MAP_FAILED, 0))
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return errno;
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/* 'size' is guaranteed to be greater than zero. So we can
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never get a NULL pointer back from MMAP. */
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assert (mem != NULL);
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/* Place the thread descriptor at the end of the stack. */
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pd = (struct pthread *) ((char *) mem + size) - 1;
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/* Remember the stack-related values. */
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pd->stackblock = mem;
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pd->stackblock_size = size;
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/* We allocated the first block thread-specific data array.
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This address will not change for the lifetime of this
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descriptor. */
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pd->specific[0] = pd->specific_1stblock;
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/* Initialize the lock. */
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pd->lock = LLL_LOCK_INITIALIZER;
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/* There is at least one more thread. */
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pd->header.data.multiple_threads = 1;
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#ifdef NEED_DL_SYSINFO
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/* Copy the sysinfo value from the parent. */
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pd->header.data.sysinfo
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= THREAD_GETMEM (THREAD_SELF, header.data.sysinfo);
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#endif
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/* Allocate the DTV for this thread. */
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if (_dl_allocate_tls (pd) == NULL)
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{
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/* Something went wrong. */
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int err = errno;
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/* Free the stack memory we just allocated. */
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munmap (mem, size);
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return err;
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}
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lll_lock (stack_cache_lock);
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/* And add to the list of stacks in use. */
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list_add (&pd->header.data.list, &stack_used);
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/* One more thread. */
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++nptl_nthreads;
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lll_unlock (stack_cache_lock);
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/* Note that all of the stack and the thread descriptor is
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zeroed. This means we do not have to initialize fields
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with initial value zero. This is specifically true for
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the 'tid' field which is always set back to zero once the
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stack is not used anymore and for the 'guardsize' field
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which will be read next. */
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}
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/* Create or resize the guard area if necessary. */
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if (__builtin_expect (guardsize > pd->guardsize, 0))
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{
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if (mprotect (mem, guardsize, PROT_NONE) != 0)
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{
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int err;
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mprot_error:
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err = errno;
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lll_lock (stack_cache_lock);
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/* Remove the thread from the list. */
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list_del (&pd->header.data.list);
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/* The thread is gone. */
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--nptl_nthreads;
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lll_unlock (stack_cache_lock);
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/* Free the memory regardless of whether the size of the
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cache is over the limit or not. If this piece of
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memory caused problems we better do not use it
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anymore. Uh, and we ignore possible errors. There
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is nothing we could do. */
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(void) munmap (mem, size);
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return err;
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}
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pd->guardsize = guardsize;
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}
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else if (__builtin_expect (pd->guardsize - guardsize > size - reqsize,
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0))
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{
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/* The old guard area is too large. */
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if (mprotect ((char *) mem + guardsize,
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pd->guardsize - guardsize,
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PROT_READ | PROT_WRITE | PROT_EXEC) != 0)
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goto mprot_error;
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pd->guardsize = guardsize;
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}
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}
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/* We place the thread descriptor at the end of the stack. */
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*pdp = pd;
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#if TLS_TCB_AT_TP
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/* The stack begin before the TCB and the static TLS block. */
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*stack = ((char *) (pd + 1) - __static_tls_size);
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#else
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# error "Implement me"
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#endif
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return 0;
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}
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/* This is how the function is called. We do it this way to allow
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other variants of the function to have more parameters. */
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#define ALLOCATE_STACK(attr, pd) allocate_stack (attr, pd, &stackaddr)
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void
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__deallocate_stack (struct pthread *pd)
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{
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lll_lock (stack_cache_lock);
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/* Remove the thread from the list of threads with user defined
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stacks. */
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list_del (&pd->header.data.list);
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/* Not much to do. Just free the mmap()ed memory. Note that we do
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not reset the 'used' flag in the 'tid' field. This is done by
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the kernel. If no thread has been created yet this field is
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still zero. */
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if (__builtin_expect (! pd->user_stack, 1))
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(void) queue_stack (pd);
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else
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/* Free the memory associated with the ELF TLS. */
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_dl_deallocate_tls (pd, false);
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/* One less thread. */
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--nptl_nthreads;
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lll_unlock (stack_cache_lock);
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}
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/* In case of a fork() call the memory allocation in the child will be
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the same but only one thread is running. All stacks except that of
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the one running thread are not used anymore. We have to recycle
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them. */
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void
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__reclaim_stacks (void)
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{
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struct pthread *self = (struct pthread *) THREAD_SELF;
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/* No locking necessary. The caller is the only stack in use. */
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/* Mark all stacks except the still running one as free. */
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list_t *runp;
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list_for_each (runp, &stack_used)
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{
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struct pthread *curp;
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curp = list_entry (runp, struct pthread, header.data.list);
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if (curp != self)
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{
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/* This marks the stack as free. */
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curp->tid = 0;
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/* Account for the size of the stack. */
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stack_cache_actsize += curp->stackblock_size;
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}
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}
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/* Add the stack of all running threads to the cache. */
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list_splice (&stack_used, &stack_cache);
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/* Remove the entry for the current thread to from the cache list
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and add it to the list of running threads. Which of the two
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lists is decided by the user_stack flag. */
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list_del (&self->header.data.list);
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/* Re-initialize the lists for all the threads. */
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INIT_LIST_HEAD (&stack_used);
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INIT_LIST_HEAD (&__stack_user);
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if (__builtin_expect (THREAD_GETMEM (self, user_stack), 0))
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list_add (&self->header.data.list, &__stack_user);
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else
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list_add (&self->header.data.list, &stack_used);
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/* There is one thread running. */
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nptl_nthreads = 1;
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/* Initialize the lock. */
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stack_cache_lock = LLL_LOCK_INITIALIZER;
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}
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