gold/descriptors.cc

   1 // descriptors.cc -- manage file descriptors for gold
   2
   3 // Copyright 2008 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           return descriptor;
  79         }
  80     }
  81
  82   while (true)
  83     {
  84       int new_descriptor = ::open(name, flags, mode);
  85       if (new_descriptor < 0
  86           && errno != ENFILE
  87           && errno != EMFILE)
  88         {
  89           if (descriptor >= 0 && errno == ENOENT)
  90             {
  91               {
  92                 Hold_lock hl(*this->lock_);
  93
  94                 gold_error(_("file %s was removed during the link"),
  95                            this->open_descriptors_[descriptor].name);
  96               }
  97
  98               errno = ENOENT;
  99             }
 100
 101           return new_descriptor;
 102         }
 103
 104       if (new_descriptor >= 0)
 105         {
 106           Hold_optional_lock hl(this->lock_);
 107
 108           if (static_cast<size_t>(new_descriptor)
 109               >= this->open_descriptors_.size())
 110             this->open_descriptors_.resize(new_descriptor + 64);
 111
 112           Open_descriptor* pod = &this->open_descriptors_[new_descriptor];
 113           pod->name = name;
 114           pod->stack_next = -1;
 115           pod->inuse = true;
 116           pod->is_write = (flags & O_ACCMODE) != O_RDONLY;
 117
 118           if (!pod->is_claimed)
 119             ++this->current_;
 120           pod->is_claimed = false;
 121           if (this->current_ >= this->limit_)
 122             this->close_some_descriptor();
 123
 124           return new_descriptor;
 125         }
 126
 127       // We ran out of file descriptors.
 128       {
 129         Hold_optional_lock hl(this->lock_);
 130
 131         this->limit_ = this->current_ - 16;
 132         if (this->limit_ < 8)
 133           this->limit_ = 8;
 134         if (!this->close_some_descriptor())
 135           gold_fatal(_("out of file descriptors and couldn't close any"));
 136       }
 137     }
 138 }
 139
 140 // Release a descriptor.
 141
 142 void
 143 Descriptors::release(int descriptor, bool permanent)
 144 {
 145   Hold_optional_lock hl(this->lock_);
 146
 147   gold_assert(descriptor >= 0
 148               && (static_cast<size_t>(descriptor)
 149                   < this->open_descriptors_.size()));
 150   Open_descriptor* pod = &this->open_descriptors_[descriptor];
 151
 152   if (permanent
 153       || (this->current_ > this->limit_ && !pod->is_write))
 154     {
 155       if (::close(descriptor) < 0)
 156         gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
 157       pod->name = NULL;
 158       --this->current_;
 159     }
 160   else
 161     {
 162       pod->inuse = false;
 163       if (!pod->is_write)
 164         {
 165           pod->stack_next = this->stack_top_;
 166           this->stack_top_ = descriptor;
 167         }
 168     }
 169 }
 170
 171 // Claim the file descriptor DESCRIPTOR for a plugin.  This effectively
 172 // removes the descriptor from the pool of linker-managed descriptors,
 173 // as the plugin will assume responsibility for closing it.
 174 // The IS_CLAIMED flag allows us to recognize when a file descriptor
 175 // has been reused after being closed by the plugin.
 176
 177 void
 178 Descriptors::claim_for_plugin(int descriptor)
 179 {
 180   Hold_lock hl(*this->lock_);
 181
 182   gold_assert(descriptor >= 0
 183               && (static_cast<size_t>(descriptor)
 184                   < this->open_descriptors_.size()));
 185   Open_descriptor* pod = &this->open_descriptors_[descriptor];
 186   pod->is_claimed = true;
 187 }
 188
 189 // Close some descriptor.  The lock is held when this is called.  We
 190 // close the descriptor on the top of the free stack.  Note that this
 191 // is the opposite of an LRU algorithm--we close the most recently
 192 // used descriptor.  That is because the linker tends to cycle through
 193 // all the files; after we release a file, we are unlikely to need it
 194 // again until we have looked at all the other files.  Return true if
 195 // we closed a descriptor.
 196
 197 bool
 198 Descriptors::close_some_descriptor()
 199 {
 200   int last = -1;
 201   int i = this->stack_top_;
 202   while (i >= 0)
 203     {
 204       gold_assert(static_cast<size_t>(i) < this->open_descriptors_.size());
 205       Open_descriptor* pod = &this->open_descriptors_[i];
 206       if (!pod->inuse && !pod->is_write)
 207         {
 208           if (::close(i) < 0)
 209             gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
 210           --this->current_;
 211           pod->name = NULL;
 212           if (last < 0)
 213             this->stack_top_ = pod->stack_next;
 214           else
 215             this->open_descriptors_[last].stack_next = pod->stack_next;
 216           return true;
 217         }
 218       last = i;
 219       i = pod->stack_next;
 220     }
 221
 222   // We couldn't find any descriptors to close.  This is weird but not
 223   // necessarily an error.
 224   return false;
 225 }
 226
 227 // The single global variable which manages descriptors.
 228
 229 Descriptors descriptors;
 230
 231 } // End namespace gold.