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           ++this->current_;
 119           if (this->current_ >= this->limit_)
 120             this->close_some_descriptor();
 121
 122           return new_descriptor;
 123         }
 124
 125       // We ran out of file descriptors.
 126       {
 127         Hold_optional_lock hl(this->lock_);
 128
 129         this->limit_ = this->current_ - 16;
 130         if (this->limit_ < 8)
 131           this->limit_ = 8;
 132         if (!this->close_some_descriptor())
 133           gold_fatal(_("out of file descriptors and couldn't close any"));
 134       }
 135     }
 136 }
 137
 138 // Release a descriptor.
 139
 140 void
 141 Descriptors::release(int descriptor, bool permanent)
 142 {
 143   Hold_optional_lock hl(this->lock_);
 144
 145   gold_assert(descriptor >= 0
 146               && (static_cast<size_t>(descriptor)
 147                   < this->open_descriptors_.size()));
 148   Open_descriptor* pod = &this->open_descriptors_[descriptor];
 149
 150   if (permanent
 151       || (this->current_ > this->limit_ && !pod->is_write))
 152     {
 153       if (::close(descriptor) < 0)
 154         gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
 155       pod->name = NULL;
 156       --this->current_;
 157     }
 158   else
 159     {
 160       pod->inuse = false;
 161       if (!pod->is_write)
 162         {
 163           pod->stack_next = this->stack_top_;
 164           this->stack_top_ = descriptor;
 165         }
 166     }
 167 }
 168
 169 // Close some descriptor.  The lock is held when this is called.  We
 170 // close the descriptor on the top of the free stack.  Note that this
 171 // is the opposite of an LRU algorithm--we close the most recently
 172 // used descriptor.  That is because the linker tends to cycle through
 173 // all the files; after we release a file, we are unlikely to need it
 174 // again until we have looked at all the other files.  Return true if
 175 // we closed a descriptor.
 176
 177 bool
 178 Descriptors::close_some_descriptor()
 179 {
 180   int last = -1;
 181   int i = this->stack_top_;
 182   while (i >= 0)
 183     {
 184       gold_assert(static_cast<size_t>(i) < this->open_descriptors_.size());
 185       Open_descriptor* pod = &this->open_descriptors_[i];
 186       if (!pod->inuse && !pod->is_write)
 187         {
 188           if (::close(i) < 0)
 189             gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
 190           --this->current_;
 191           pod->name = NULL;
 192           if (last < 0)
 193             this->stack_top_ = pod->stack_next;
 194           else
 195             this->open_descriptors_[last].stack_next = pod->stack_next;
 196           return true;
 197         }
 198       last = i;
 199       i = pod->stack_next;
 200     }
 201
 202   // We couldn't find any descriptors to close.  This is weird but not
 203   // necessarily an error.
 204   return false;
 205 }
 206
 207 // The single global variable which manages descriptors.
 208
 209 Descriptors descriptors;
 210
 211 } // End namespace gold.