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 "options.h"
  32 #include "gold-threads.h"
  33 #include "descriptors.h"
  34
  35 // Very old systems may not define FD_CLOEXEC.
  36 #ifndef FD_CLOEXEC
  37 #define FD_CLOEXEC 1
  38 #endif
  39
  40 // O_CLOEXEC is only available on newer systems.
  41 #ifndef O_CLOEXEC
  42 #define O_CLOEXEC 0
  43 #endif
  44
  45 namespace gold
  46 {
  47
  48 // Class Descriptors.
  49
  50 // The default for limit_ is meant to simply be large.  It gets
  51 // adjusted downward if we run out of file descriptors.
  52
  53 Descriptors::Descriptors()
  54   : lock_(NULL), initialize_lock_(&this->lock_), open_descriptors_(),
  55     stack_top_(-1), current_(0), limit_(8192 - 16)
  56 {
  57   this->open_descriptors_.reserve(128);
  58 }
  59
  60 // Open a file.
  61
  62 int
  63 Descriptors::open(int descriptor, const char* name, int flags, int mode)
  64 {
  65   // We don't initialize this until we are called, because we can't
  66   // initialize a Lock until we have parsed the options to find out
  67   // whether we are running with threads.  We can be called before
  68   // options are valid when reading a linker script.
  69   bool lock_initialized = this->initialize_lock_.initialize();
  70
  71   gold_assert(lock_initialized || descriptor < 0);
  72
  73   if (descriptor >= 0)
  74     {
  75       Hold_lock hl(*this->lock_);
  76
  77       gold_assert(static_cast<size_t>(descriptor)
  78                   < this->open_descriptors_.size());
  79       Open_descriptor* pod = &this->open_descriptors_[descriptor];
  80       if (pod->name == name
  81           || (pod->name != NULL && strcmp(pod->name, name) == 0))
  82         {
  83           gold_assert(!pod->inuse);
  84           pod->inuse = true;
  85           if (descriptor == this->stack_top_)
  86             {
  87               this->stack_top_ = pod->stack_next;
  88               pod->stack_next = -1;
  89               pod->is_on_stack = false;
  90             }
  91           return descriptor;
  92         }
  93     }
  94
  95   while (true)
  96     {
  97       // We always want to set the close-on-exec flag; we don't
  98       // require callers to pass it.
  99       flags |= O_CLOEXEC;
 100
 101       int new_descriptor = ::open(name, flags, mode);
 102       if (new_descriptor < 0
 103           && errno != ENFILE
 104           && errno != EMFILE)
 105         {
 106           if (descriptor >= 0 && errno == ENOENT)
 107             {
 108               {
 109                 Hold_lock hl(*this->lock_);
 110
 111                 gold_error(_("file %s was removed during the link"),
 112                            this->open_descriptors_[descriptor].name);
 113               }
 114
 115               errno = ENOENT;
 116             }
 117
 118           return new_descriptor;
 119         }
 120
 121       if (new_descriptor >= 0)
 122         {
 123           // If we have any plugins, we really do need to set the
 124           // close-on-exec flag, even if O_CLOEXEC is not defined.
 125           // FIXME: In some cases O_CLOEXEC may be defined in the
 126           // header file but not supported by the kernel.
 127           // Unfortunately there doesn't seem to be any obvious way to
 128           // detect that, as unknown flags passed to open are ignored.
 129           if (O_CLOEXEC == 0
 130               && parameters->options_valid()
 131               && parameters->options().has_plugins())
 132             fcntl(new_descriptor, F_SETFD, FD_CLOEXEC);
 133
 134           {
 135             Hold_optional_lock hl(this->lock_);
 136
 137             if (static_cast<size_t>(new_descriptor)
 138                 >= this->open_descriptors_.size())
 139               this->open_descriptors_.resize(new_descriptor + 64);
 140
 141             Open_descriptor* pod = &this->open_descriptors_[new_descriptor];
 142             pod->name = name;
 143             pod->stack_next = -1;
 144             pod->inuse = true;
 145             pod->is_write = (flags & O_ACCMODE) != O_RDONLY;
 146             pod->is_on_stack = false;
 147
 148             ++this->current_;
 149             if (this->current_ >= this->limit_)
 150               this->close_some_descriptor();
 151
 152             return new_descriptor;
 153           }
 154         }
 155
 156       // We ran out of file descriptors.
 157       {
 158         Hold_optional_lock hl(this->lock_);
 159
 160         this->limit_ = this->current_ - 16;
 161         if (this->limit_ < 8)
 162           this->limit_ = 8;
 163         if (!this->close_some_descriptor())
 164           gold_fatal(_("out of file descriptors and couldn't close any"));
 165       }
 166     }
 167 }
 168
 169 // Release a descriptor.
 170
 171 void
 172 Descriptors::release(int descriptor, bool permanent)
 173 {
 174   Hold_optional_lock hl(this->lock_);
 175
 176   gold_assert(descriptor >= 0
 177               && (static_cast<size_t>(descriptor)
 178                   < this->open_descriptors_.size()));
 179   Open_descriptor* pod = &this->open_descriptors_[descriptor];
 180
 181   if (permanent
 182       || (this->current_ > this->limit_ && !pod->is_write))
 183     {
 184       if (::close(descriptor) < 0)
 185         gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
 186       pod->name = NULL;
 187       --this->current_;
 188     }
 189   else
 190     {
 191       pod->inuse = false;
 192       if (!pod->is_write && !pod->is_on_stack)
 193         {
 194           pod->stack_next = this->stack_top_;
 195           this->stack_top_ = descriptor;
 196           pod->is_on_stack = true;
 197         }
 198     }
 199 }
 200
 201 // Close some descriptor.  The lock is held when this is called.  We
 202 // close the descriptor on the top of the free stack.  Note that this
 203 // is the opposite of an LRU algorithm--we close the most recently
 204 // used descriptor.  That is because the linker tends to cycle through
 205 // all the files; after we release a file, we are unlikely to need it
 206 // again until we have looked at all the other files.  Return true if
 207 // we closed a descriptor.
 208
 209 bool
 210 Descriptors::close_some_descriptor()
 211 {
 212   int last = -1;
 213   int i = this->stack_top_;
 214   while (i >= 0)
 215     {
 216       gold_assert(static_cast<size_t>(i) < this->open_descriptors_.size());
 217       Open_descriptor* pod = &this->open_descriptors_[i];
 218       if (!pod->inuse && !pod->is_write)
 219         {
 220           if (::close(i) < 0)
 221             gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
 222           --this->current_;
 223           pod->name = NULL;
 224           if (last < 0)
 225             this->stack_top_ = pod->stack_next;
 226           else
 227             this->open_descriptors_[last].stack_next = pod->stack_next;
 228           pod->stack_next = -1;
 229           pod->is_on_stack = false;
 230           return true;
 231         }
 232       last = i;
 233       i = pod->stack_next;
 234     }
 235
 236   // We couldn't find any descriptors to close.  This is weird but not
 237   // necessarily an error.
 238   return false;
 239 }
 240
 241 // The single global variable which manages descriptors.
 242
 243 Descriptors descriptors;
 244
 245 } // End namespace gold.