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-rw-r--r--nptl/allocatestack.c507
1 files changed, 507 insertions, 0 deletions
diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
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+/* 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;
+}