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Diffstat (limited to 'nptl/allocatestack.c')
| -rw-r--r-- | nptl/allocatestack.c | 507 |
1 files changed, 507 insertions, 0 deletions
diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c new file mode 100644 index 0000000..2aaaaec --- /dev/null +++ b/nptl/allocatestack.c @@ -0,0 +1,507 @@ +/* Copyright (C) 2002 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Ulrich Drepper <drepper@redhat.com>, 2002. + + 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, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <assert.h> +#include <errno.h> +#include <stdint.h> +#include <string.h> +#include <unistd.h> +#include <sys/mman.h> +#include <sys/param.h> +#include <tls.h> + + + + +/* Most architectures have exactly one stack pointer. Some have more. */ +#define STACK_VARIABLES void *stackaddr + +/* How to pass the values to the 'create_thread' function. */ +#define STACK_VARIABLES_ARGS stackaddr + +/* How to declare function which gets there parameters. */ +#define STACK_VARIABLES_PARMS void *stackaddr + + +/* Default alignment of stack. */ +#ifndef STACK_ALIGN +# define STACK_ALIGN __alignof__ (long double) +#endif + +/* Default value for minimal stack size after allocating thread + descriptor and guard. */ +#ifndef MINIMAL_REST_STACK +# define MINIMAL_REST_STACK 4096 +#endif + + + + +/* Cache handling for not-yet free stacks. */ + +/* Maximum size in kB of cache. */ +static size_t stack_cache_maxsize = 40 * 1024 * 1024; /* 40MiBi by default. */ +static size_t stack_cache_actsize; + +/* Mutex protecting this variable. */ +static lll_lock_t stack_cache_lock = LLL_LOCK_INITIALIZER; + +/* List of queued stack frames. */ +static LIST_HEAD (stack_cache); + +/* List of the stacks in use. */ +static LIST_HEAD (stack_used); + +/* List of the threads with user provided stacks in use. */ +LIST_HEAD (__stack_user); + +/* Number of threads running. */ +static unsigned int nptl_nthreads = 1; + + +/* Check whether the stack is still used or not. */ +#define FREE_P(descr) ((descr)->tid == 0) + + +/* We create a double linked list of all cache entries. Double linked + because this allows removing entries from the end. */ + + +/* Get a stack frame from the cache. We have to match by size since + some blocks might be too small or far too large. */ +static struct pthread * +get_cached_stack (size_t *sizep, void **memp) +{ + size_t size = *sizep; + struct pthread *result = NULL; + list_t *entry; + + lll_lock (stack_cache_lock); + + /* Search the cache for a matching entry. We search for the + smallest stack which has at least the required size. Note that + in normal situations the size of all allocated stacks is the + same. As the very least there are only a few different sizes. + Therefore this loop will exit early most of the time with an + exact match. */ + list_for_each (entry, &stack_cache) + { + struct pthread *curr; + + curr = list_entry(entry, struct pthread, header.data.list); + if (FREE_P (curr) && curr->stackblock_size >= size) + { + if (curr->stackblock_size == size) + { + result = curr; + break; + } + + if (result->stackblock_size > curr->stackblock_size) + result = curr; + } + } + + if (__builtin_expect (result == NULL, 0) + /* Make sure the size difference is not too excessive. In that + case we do not use the block. */ + || __builtin_expect (result->stackblock_size > 4 * size, 0)) + { + /* Release the lock. */ + lll_unlock (stack_cache_lock); + + return NULL; + } + + /* Dequeue the entry. */ + list_del (&result->header.data.list); + + /* And add to the list of stacks in use. */ + list_add (&result->header.data.list, &stack_used); + + /* One more thread. */ + ++nptl_nthreads; + + /* And decrease the cache size. */ + stack_cache_actsize -= result->stackblock_size; + + /* Release the lock early. */ + lll_unlock (stack_cache_lock); + + + *sizep = result->stackblock_size; + *memp = result->stackblock; + + /* Cancellation handling is back to the default. */ + result->cancelhandling = 0; + result->cleanup = NULL; + + /* No pending event. */ + result->nextevent = NULL; + + /* Clear the DTV. */ + dtv_t *dtv = GET_DTV (result); + memset (dtv, '\0', (dtv[-1].counter + 1) * sizeof (dtv_t)); + + /* Re-initialize the TLS. */ + return _dl_allocate_tls_init (result); +} + + +/* Add a stack frame which is not used anymore to the stack. Must be + called with the cache lock held. */ +static void +queue_stack (struct pthread *stack) +{ + /* We unconditionally add the stack to the list. The memory may + still be in use but it will not be reused until the kernel marks + the stack as not used anymore. */ + list_add (&stack->header.data.list, &stack_cache); + + stack_cache_actsize += stack->stackblock_size; + if (__builtin_expect (stack_cache_actsize > stack_cache_maxsize, 0)) + { + /* We reduce the size of the cache. Remove the last entries + until the size is below the limit. */ + list_t *entry; + list_t *prev; + + /* Search from the end of the list. */ + list_for_each_prev_safe (entry, prev, &stack_cache) + { + struct pthread *curr; + + curr = list_entry(entry, struct pthread, header.data.list); + if (FREE_P (curr)) + { + /* Unlink the block. */ + list_del (entry); + + /* Account for the freed memory. */ + stack_cache_actsize -= curr->stackblock_size; + + /* Free the memory associated with the ELF TLS. */ + _dl_deallocate_tls (curr, false); + + /* Remove this block. This should never fail. If it + does something is really wrong. */ + if (munmap (curr->stackblock, curr->stackblock_size) != 0) + abort (); + + /* Maybe we have freed enough. */ + if (stack_cache_actsize <= stack_cache_maxsize) + break; + } + } + } +} + + + +static int +allocate_stack (const struct pthread_attr *attr, struct pthread **pdp, + void **stack) +{ + struct pthread *pd; + size_t size; + size_t pagesize = __sysconf (_SC_PAGESIZE); + + assert (attr != NULL); + assert (powerof2 (pagesize)); + assert (TCB_ALIGNMENT >= STACK_ALIGN); + + /* Get the stack size from the attribute if it is set. Otherwise we + use the default we determined at start time. */ + size = attr->stacksize ?: __default_stacksize; + + /* Get memory for the stack. */ + if (__builtin_expect (attr->flags & ATTR_FLAG_STACKADDR, 0)) + { + uintptr_t adj; + + /* If the user also specified the size of the stack make sure it + is large enough. */ + if (attr->stacksize != 0 + && attr->stacksize < (__static_tls_size + MINIMAL_REST_STACK)) + return EINVAL; + + /* Adjust stack size for alignment of the TLS block. */ + adj = ((uintptr_t) attr->stackaddr) & (__static_tls_align - 1); + assert (size > adj); + + /* The user provided some memory. Let's hope it matches the + size... We do not allocate guard pages if the user provided + the stack. It is the user's responsibility to do this if it + is wanted. */ + pd = (struct pthread *) (((uintptr_t) attr->stackaddr - adj) + & ~(__alignof (struct pthread) - 1)) - 1; + + /* The user provided stack memory need not be cleared. */ + memset (pd, '\0', sizeof (struct pthread)); + + /* The first TSD block is included in the TCB. */ + pd->specific[0] = pd->specific_1stblock; + + /* Initialize the lock. */ + pd->lock = LLL_LOCK_INITIALIZER; + + /* Remember the stack-related values. Signal that this stack + must not be put into the stack cache. */ + pd->stackblock = (char *) attr->stackaddr - size; + pd->stackblock_size = size - adj; + + /* This is a user-provided stack. */ + pd->user_stack = true; + + /* Allocate the DTV for this thread. */ + if (_dl_allocate_tls (pd) == NULL) + /* Something went wrong. */ + return errno; + + + lll_lock (stack_cache_lock); + + /* And add to the list of stacks in use. */ + list_add (&pd->header.data.list, &__stack_user); + + /* One more thread. */ + ++nptl_nthreads; + + lll_unlock (stack_cache_lock); + } + else + { + /* Allocate some anonymous memory. If possible use the + cache. */ + size_t guardsize; + size_t reqsize; + void *mem; + + /* Adjust the stack size for alignment. */ + size &= ~(__static_tls_align - 1); + assert (size != 0); + + /* Make sure the size of the stack is enough for the guard and + eventually the thread descriptor. */ + guardsize = (attr->guardsize + pagesize - 1) & ~(pagesize - 1); + if (__builtin_expect (size < (guardsize + __static_tls_size + + MINIMAL_REST_STACK), 0)) + /* The stack is too small (or the guard too large). */ + return EINVAL; + + reqsize = size; + pd = get_cached_stack (&size, &mem); + if (pd == NULL) + { + mem = mmap (NULL, size, PROT_READ | PROT_WRITE | PROT_EXEC, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + + if (__builtin_expect (mem == MAP_FAILED, 0)) + return errno; + + /* 'size' is guaranteed to be greater than zero. So we can + never get a NULL pointer back from MMAP. */ + assert (mem != NULL); + + /* Place the thread descriptor at the end of the stack. */ + pd = (struct pthread *) ((char *) mem + size) - 1; + + /* Remember the stack-related values. */ + pd->stackblock = mem; + pd->stackblock_size = size; + + /* We allocated the first block thread-specific data array. + This address will not change for the lifetime of this + descriptor. */ + pd->specific[0] = pd->specific_1stblock; + + /* Initialize the lock. */ + pd->lock = LLL_LOCK_INITIALIZER; + + /* Allocate the DTV for this thread. */ + if (_dl_allocate_tls (pd) == NULL) + { + /* Something went wrong. */ + int err = errno; + + /* Free the stack memory we just allocated. */ + munmap (mem, size); + + return err; + } + + + lll_lock (stack_cache_lock); + + /* And add to the list of stacks in use. */ + list_add (&pd->header.data.list, &stack_used); + + /* One more thread. */ + ++nptl_nthreads; + + lll_unlock (stack_cache_lock); + + + /* Note that all of the stack and the thread descriptor is + zeroed. This means we do not have to initialize fields + with initial value zero. This is specifically true for + the 'tid' field which is always set back to zero once the + stack is not used anymore and for the 'guardsize' field + which will be read next. */ + } + + /* Create or resize the guard area if necessary. */ + if (__builtin_expect (guardsize > pd->guardsize, 0)) + { + if (mprotect (mem, guardsize, PROT_NONE) != 0) + { + int err; + mprot_error: + err = errno; + + lll_lock (stack_cache_lock); + + /* Remove the thread from the list. */ + list_del (&pd->header.data.list); + + /* The thread is gone. */ + --nptl_nthreads; + + lll_unlock (stack_cache_lock); + + /* Free the memory regardless of whether the size of the + cache is over the limit or not. If this piece of + memory caused problems we better do not use it + anymore. Uh, and we ignore possible errors. There + is nothing we could do. */ + (void) munmap (mem, size); + + return err; + } + + pd->guardsize = guardsize; + } + else if (__builtin_expect (pd->guardsize - guardsize > size - reqsize, + 0)) + { + /* The old guard area is too large. */ + if (mprotect ((char *) mem + guardsize, + pd->guardsize - guardsize, + PROT_READ | PROT_WRITE | PROT_EXEC) != 0) + goto mprot_error; + + pd->guardsize = guardsize; + } + } + + /* We place the thread descriptor at the end of the stack. */ + *pdp = pd; + +#if TLS_TCB_AT_TP + /* The stack begin before the TCB and the static TLS block. */ + *stack = ((char *) (pd + 1) - __static_tls_size); +#else +# error "Implement me" +#endif + + return 0; +} + +/* This is how the function is called. We do it this way to allow + other variants of the function to have more parameters. */ +#define ALLOCATE_STACK(attr, pd) allocate_stack (attr, pd, &stackaddr) + + +void +__deallocate_stack (struct pthread *pd) +{ + lll_lock (stack_cache_lock); + + /* Remove the thread from the list of threads with user defined + stacks. */ + list_del (&pd->header.data.list); + + /* Not much to do. Just free the mmap()ed memory. Note that we do + not reset the 'used' flag in the 'tid' field. This is done by + the kernel. If no thread has been created yet this field is + still zero. */ + if (__builtin_expect (! pd->user_stack, 1)) + (void) queue_stack (pd); + else + /* Free the memory associated with the ELF TLS. */ + _dl_deallocate_tls (pd, false); + + /* One less thread. */ + --nptl_nthreads; + + lll_unlock (stack_cache_lock); +} + + +/* In case of a fork() call the memory allocation in the child will be + the same but only one thread is running. All stacks except that of + the one running thread are not used anymore. We have to recycle + them. */ +void +__reclaim_stacks (void) +{ + struct pthread *self = (struct pthread *) THREAD_SELF; + + /* No locking necessary. The caller is the only stack in use. */ + + /* Mark all stacks except the still running one as free. */ + list_t *runp; + list_for_each (runp, &stack_used) + { + struct pthread *curp; + + curp = list_entry (runp, struct pthread, header.data.list); + if (curp != self) + { + /* This marks the stack as free. */ + curp->tid = 0; + + /* Account for the size of the stack. */ + stack_cache_actsize += curp->stackblock_size; + } + } + + /* Add the stack of all running threads to the cache. */ + list_splice (&stack_used, &stack_cache); + + /* Remove the entry for the current thread to from the cache list + and add it to the list of running threads. Which of the two + lists is decided by the user_stack flag. */ + list_del (&self->header.data.list); + + /* Re-initialize the lists for all the threads. */ + INIT_LIST_HEAD (&stack_used); + INIT_LIST_HEAD (&__stack_user); + + if (__builtin_expect (THREAD_GETMEM (self, user_stack), 0)) + list_add (&self->header.data.list, &__stack_user); + else + list_add (&self->header.data.list, &stack_used); + + /* There is one thread running. */ + nptl_nthreads = 1; + + /* Initialize the lock. */ + stack_cache_lock = LLL_LOCK_INITIALIZER; +} |