gold/descriptors.cc

   1 // descriptors.cc -- manage file descriptors for gold
   2
   3 // Copyright 2008, 2009 Free Software Foundation, Inc.
   4 // Written by Ian Lance Taylor <iant@google.com>.
   5
   6 // This file is part of gold.
   7
   8 // This program is free software; you can redistribute it and/or modify
   9 // it under the terms of the GNU General Public License as published by
  10 // the Free Software Foundation; either version 3 of the License, or
  11 // (at your option) any later version.
  12
  13 // This program is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17
  18 // You should have received a copy of the GNU General Public License
  19 // along with this program; if not, write to the Free Software
  20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  21 // MA 02110-1301, USA.
  22
  23 #include "gold.h"
  24
  25 #include <cerrno>
  26 #include <cstring>
  27 #include <fcntl.h>
  28 #include <unistd.h>
  29
  30 #include "parameters.h"
  31 #include "gold-threads.h"
  32 #include "descriptors.h"
  33
  34 namespace gold
  35 {
  36
  37 // Class Descriptors.
  38
  39 // The default for limit_ is meant to simply be large.  It gets
  40 // adjusted downward if we run out of file descriptors.
  41
  42 Descriptors::Descriptors()
  43   : lock_(NULL), open_descriptors_(), stack_top_(-1), current_(0),
  44     limit_(8192 - 16)
  45 {
  46   this->open_descriptors_.reserve(128);
  47 }
  48
  49 // Open a file.
  50
  51 int
  52 Descriptors::open(int descriptor, const char* name, int flags, int mode)
  53 {
  54   // We don't initialize this until we are called, because we can't
  55   // initialize a Lock until we have parsed the options to find out
  56   // whether we are running with threads.  We can be called before
  57   // options are valid when reading a linker script.
  58   if (this->lock_ == NULL)
  59     {
  60       if (parameters->options_valid())
  61         this->lock_ = new Lock();
  62       else
  63         gold_assert(descriptor < 0);
  64     }
  65
  66   if (descriptor >= 0)
  67     {
  68       Hold_lock hl(*this->lock_);
  69
  70       gold_assert(static_cast<size_t>(descriptor)
  71                   < this->open_descriptors_.size());
  72       Open_descriptor* pod = &this->open_descriptors_[descriptor];
  73       if (pod->name == name
  74           || (pod->name != NULL && strcmp(pod->name, name) == 0))
  75         {
  76           gold_assert(!pod->inuse);
  77           pod->inuse = true;
  78           if (descriptor == this->stack_top_)
  79             {
  80               this->stack_top_ = pod->stack_next;
  81               pod->stack_next = -1;
  82               pod->is_on_stack = false;
  83             }
  84           return descriptor;
  85         }
  86     }
  87
  88   while (true)
  89     {
  90       int new_descriptor = ::open(name, flags, mode);
  91       if (new_descriptor < 0
  92           && errno != ENFILE
  93           && errno != EMFILE)
  94         {
  95           if (descriptor >= 0 && errno == ENOENT)
  96             {
  97               {
  98                 Hold_lock hl(*this->lock_);
  99
 100                 gold_error(_("file %s was removed during the link"),
 101                            this->open_descriptors_[descriptor].name);
 102               }
 103
 104               errno = ENOENT;
 105             }
 106
 107           return new_descriptor;
 108         }
 109
 110       if (new_descriptor >= 0)
 111         {
 112           Hold_optional_lock hl(this->lock_);
 113
 114           if (static_cast<size_t>(new_descriptor)
 115               >= this->open_descriptors_.size())
 116             this->open_descriptors_.resize(new_descriptor + 64);
 117
 118           Open_descriptor* pod = &this->open_descriptors_[new_descriptor];
 119           pod->name = name;
 120           pod->stack_next = -1;
 121           pod->inuse = true;
 122           pod->is_write = (flags & O_ACCMODE) != O_RDONLY;
 123           pod->is_on_stack = false;
 124
 125           ++this->current_;
 126           if (this->current_ >= this->limit_)
 127             this->close_some_descriptor();
 128
 129           return new_descriptor;
 130         }
 131
 132       // We ran out of file descriptors.
 133       {
 134         Hold_optional_lock hl(this->lock_);
 135
 136         this->limit_ = this->current_ - 16;
 137         if (this->limit_ < 8)
 138           this->limit_ = 8;
 139         if (!this->close_some_descriptor())
 140           gold_fatal(_("out of file descriptors and couldn't close any"));
 141       }
 142     }
 143 }
 144
 145 // Release a descriptor.
 146
 147 void
 148 Descriptors::release(int descriptor, bool permanent)
 149 {
 150   Hold_optional_lock hl(this->lock_);
 151
 152   gold_assert(descriptor >= 0
 153               && (static_cast<size_t>(descriptor)
 154                   < this->open_descriptors_.size()));
 155   Open_descriptor* pod = &this->open_descriptors_[descriptor];
 156
 157   if (permanent
 158       || (this->current_ > this->limit_ && !pod->is_write))
 159     {
 160       if (::close(descriptor) < 0)
 161         gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
 162       pod->name = NULL;
 163       --this->current_;
 164     }
 165   else
 166     {
 167       pod->inuse = false;
 168       if (!pod->is_write && !pod->is_on_stack)
 169         {
 170           pod->stack_next = this->stack_top_;
 171           this->stack_top_ = descriptor;
 172           pod->is_on_stack = true;
 173         }
 174     }
 175 }
 176
 177 // Close some descriptor.  The lock is held when this is called.  We
 178 // close the descriptor on the top of the free stack.  Note that this
 179 // is the opposite of an LRU algorithm--we close the most recently
 180 // used descriptor.  That is because the linker tends to cycle through
 181 // all the files; after we release a file, we are unlikely to need it
 182 // again until we have looked at all the other files.  Return true if
 183 // we closed a descriptor.
 184
 185 bool
 186 Descriptors::close_some_descriptor()
 187 {
 188   int last = -1;
 189   int i = this->stack_top_;
 190   while (i >= 0)
 191     {
 192       gold_assert(static_cast<size_t>(i) < this->open_descriptors_.size());
 193       Open_descriptor* pod = &this->open_descriptors_[i];
 194       if (!pod->inuse && !pod->is_write)
 195         {
 196           if (::close(i) < 0)
 197             gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
 198           --this->current_;
 199           pod->name = NULL;
 200           if (last < 0)
 201             this->stack_top_ = pod->stack_next;
 202           else
 203             this->open_descriptors_[last].stack_next = pod->stack_next;
 204           pod->stack_next = -1;
 205           pod->is_on_stack = false;
 206           return true;
 207         }
 208       last = i;
 209       i = pod->stack_next;
 210     }
 211
 212   // We couldn't find any descriptors to close.  This is weird but not
 213   // necessarily an error.
 214   return false;
 215 }
 216
 217 // The single global variable which manages descriptors.
 218
 219 Descriptors descriptors;
 220
 221 } // End namespace gold.