Integrate Crystal::FdLock into File, IO::FileDescriptor and Socket

Only operations that can affect the file descriptor are counted, for
example read or write, truncating a file or changing file permissions.

Mere queries with no side effects go through normally because at worst
they will fail (they would have anyway) or return invalid information.

Author: ysbaddaden

src/crystal/system/unix/file.cr

@@ -109,7 +109,7 @@ module Crystal::System::File
   end
 
   private def system_chown(uid : Int, gid : Int)
-    ret = LibC.fchown(fd, uid, gid)
+    ret = @fd_lock.reference { LibC.fchown(fd, uid, gid) }
     raise ::File::Error.from_errno("Error changing owner", file: path) if ret == -1
   end
 
@@ -120,7 +120,7 @@ module Crystal::System::File
   end
 
   private def system_chmod(mode)
-    if LibC.fchmod(fd, mode) == -1
+    if @fd_lock.reference { LibC.fchmod(fd, mode) } == -1
       raise ::File::Error.from_errno("Error changing permissions", file: path)
     end
   end
@@ -201,12 +201,12 @@ module Crystal::System::File
             timespecs = uninitialized LibC::Timespec[2]
             timespecs[0] = Crystal::System::Time.to_timespec(atime)
             timespecs[1] = Crystal::System::Time.to_timespec(mtime)
-            LibC.futimens(fd, timespecs)
+            @fd_lock.reference { LibC.futimens(fd, timespecs) }
           {% elsif LibC.has_method?("futimes") %}
             timevals = uninitialized LibC::Timeval[2]
             timevals[0] = Crystal::System::Time.to_timeval(atime)
             timevals[1] = Crystal::System::Time.to_timeval(mtime)
-            LibC.futimes(fd, timevals)
+            @fd_lock.reference { LibC.futimes(fd, timevals) }
           {% else %}
             {% raise "Missing futimens & futimes" %}
           {% end %}
@@ -218,7 +218,7 @@ module Crystal::System::File
 
   private def system_truncate(size) : Nil
     flush
-    code = LibC.ftruncate(fd, size)
+    code = @fd_lock.reference { LibC.ftruncate(fd, size) }
     if code != 0
       raise ::File::Error.from_errno("Error truncating file", file: path)
     end

src/crystal/system/unix/file_descriptor.cr

@@ -3,6 +3,7 @@ require "termios"
 {% if flag?(:android) && LibC::ANDROID_API < 28 %}
   require "c/sys/ioctl"
 {% end %}
+require "crystal/fd_lock"
 
 # :nodoc:
 module Crystal::System::FileDescriptor
@@ -18,13 +19,15 @@ module Crystal::System::FileDescriptor
   STDOUT_HANDLE = 1
   STDERR_HANDLE = 2
 
+  @fd_lock = FdLock.new
+
   private def system_blocking?
-    flags = system_fcntl(LibC::F_GETFL)
+    flags = FileDescriptor.fcntl(fd, LibC::F_GETFL)
     !flags.bits_set? LibC::O_NONBLOCK
   end
 
   private def system_blocking=(value)
-    FileDescriptor.set_blocking(fd, value)
+    @fd_lock.reference { FileDescriptor.set_blocking(fd, value) }
   end
 
   protected def self.get_blocking(fd : Handle)
@@ -56,7 +59,7 @@ module Crystal::System::FileDescriptor
   end
 
   private def system_close_on_exec?
-    flags = system_fcntl(LibC::F_GETFD)
+    flags = FileDescriptor.fcntl(fd, LibC::F_GETFD)
     flags.bits_set? LibC::FD_CLOEXEC
   end
 
@@ -76,7 +79,7 @@ module Crystal::System::FileDescriptor
   end
 
   private def system_fcntl(cmd, arg = 0)
-    FileDescriptor.fcntl(fd, cmd, arg)
+    @fd_lock.reference { FileDescriptor.fcntl(fd, cmd, arg) }
   end
 
   def self.system_info(fd)
@@ -91,11 +94,11 @@ module Crystal::System::FileDescriptor
   end
 
   private def system_info
-    FileDescriptor.system_info fd
+    @fd_lock.reference { FileDescriptor.system_info(fd) }
   end
 
   private def system_seek(offset, whence : IO::Seek) : Nil
-    seek_value = LibC.lseek(fd, offset, whence)
+    seek_value = @fd_lock.reference { LibC.lseek(fd, offset, whence) }
 
     if seek_value == -1
       raise IO::Error.from_errno "Unable to seek", target: self
@@ -113,19 +116,23 @@ module Crystal::System::FileDescriptor
   end
 
   private def system_reopen(other : IO::FileDescriptor)
-    {% if LibC.has_method?(:dup3) %}
-      flags = other.close_on_exec? ? LibC::O_CLOEXEC : 0
-      if LibC.dup3(other.fd, fd, flags) == -1
-        raise IO::Error.from_errno("Could not reopen file descriptor")
-      end
-    {% else %}
-      Process.lock_read do
-        if LibC.dup2(other.fd, fd) == -1
-          raise IO::Error.from_errno("Could not reopen file descriptor")
-        end
-        self.close_on_exec = other.close_on_exec?
+    other.@fd_lock.reference do
+      @fd_lock.reference do
+        {% if LibC.has_method?(:dup3) %}
+          flags = other.close_on_exec? ? LibC::O_CLOEXEC : 0
+          if LibC.dup3(other.fd, fd, flags) == -1
+            raise IO::Error.from_errno("Could not reopen file descriptor")
+          end
+        {% else %}
+          Process.lock_read do
+            if LibC.dup2(other.fd, fd) == -1
+              raise IO::Error.from_errno("Could not reopen file descriptor")
+            end
+            self.close_on_exec = other.close_on_exec?
+          end
+        {% end %}
       end
-    {% end %}
+    end
 
     # Mark the handle open, since we had to have dup'd a live handle.
     @closed = false
@@ -134,8 +141,9 @@ module Crystal::System::FileDescriptor
   end
 
   private def system_close
-    event_loop.before_close(self)
-    event_loop.close(self)
+    if @fd_lock.try_close? { event_loop.before_close(self) }
+      event_loop.close(self)
+    end
   end
 
   def file_descriptor_close(&) : Nil
@@ -196,7 +204,7 @@ module Crystal::System::FileDescriptor
   end
 
   private def flock(op) : Bool
-    if 0 == LibC.flock(fd, op)
+    if 0 == @fd_lock.reference { LibC.flock(fd, op) }
       true
     else
       errno = Errno.value
@@ -209,7 +217,7 @@ module Crystal::System::FileDescriptor
   end
 
   private def system_fsync(flush_metadata = true) : Nil
-    ret =
+    ret = @fd_lock.reference do
       if flush_metadata
         LibC.fsync(fd)
       else
@@ -219,6 +227,7 @@ module Crystal::System::FileDescriptor
           LibC.fdatasync(fd)
         {% end %}
       end
+    end
 
     if ret != 0
       raise IO::Error.from_errno("Error syncing file", target: self)
@@ -246,7 +255,9 @@ module Crystal::System::FileDescriptor
   end
 
   def self.pread(file, buffer, offset)
-    bytes_read = LibC.pread(file.fd, buffer, buffer.size, offset).to_i64
+    bytes_read = file.@fd_lock.reference do
+      LibC.pread(file.fd, buffer, buffer.size, offset).to_i64
+    end
 
     if bytes_read == -1
       raise IO::Error.from_errno("Error reading file", target: file)
@@ -351,7 +362,7 @@ module Crystal::System::FileDescriptor
   @[AlwaysInline]
   private def system_tcsetattr(optional_actions, termios_p)
     {% if LibC.has_method?(:tcsetattr) %}
-      LibC.tcsetattr(fd, optional_actions, termios_p)
+      @fd_lock.reference { LibC.tcsetattr(fd, optional_actions, termios_p) }
     {% else %}
       optional_actions = optional_actions.value if optional_actions.is_a?(Termios::LineControl)
       cmd = case optional_actions
@@ -366,7 +377,7 @@ module Crystal::System::FileDescriptor
               return LibC::Int.new(-1)
             end
 
-      LibC.ioctl(fd, cmd, termios_p)
+      @fd_lock.reference { LibC.ioctl(fd, cmd, termios_p) }
     {% end %}
   end
 
@@ -385,4 +396,12 @@ module Crystal::System::FileDescriptor
     {% end %}
     termios
   end
+
+  private def system_read(slice : Bytes) : Int32
+    @fd_lock.read { event_loop.read(self, slice) }
+  end
+
+  private def system_write(slice : Bytes) : Int32
+    @fd_lock.write { event_loop.write(self, slice) }
+  end
 end

src/crystal/system/unix/socket.cr

@@ -1,6 +1,7 @@
 require "c/netdb"
 require "c/netinet/tcp"
 require "c/sys/socket"
+require "crystal/fd_lock"
 
 module Crystal::System::Socket
   {% if IO.has_constant?(:Evented) %}
@@ -9,6 +10,8 @@ module Crystal::System::Socket
 
   alias Handle = Int32
 
+  @fd_lock = FdLock.new
+
   def self.socket(family, type, protocol, blocking) : Handle
     {% if LibC.has_constant?(:SOCK_CLOEXEC) %}
       flags = type.value | LibC::SOCK_CLOEXEC
@@ -36,29 +39,29 @@ module Crystal::System::Socket
   # Tries to bind the socket to a local address.
   # Yields an `Socket::BindError` if the binding failed.
   private def system_bind(addr, addrstr, &)
-    unless LibC.bind(fd, addr, addr.size) == 0
+    unless @fd_lock.reference { LibC.bind(fd, addr, addr.size) } == 0
       yield ::Socket::BindError.from_errno("Could not bind to '#{addrstr}'")
     end
   end
 
   private def system_listen(backlog, &)
-    unless LibC.listen(fd, backlog) == 0
+    unless @fd_lock.reference { LibC.listen(fd, backlog) } == 0
       yield ::Socket::Error.from_errno("Listen failed")
     end
   end
 
   private def system_accept : {Handle, Bool}?
-    event_loop.accept(self)
+    @fd_lock.read { event_loop.accept(self) }
   end
 
   private def system_close_read
-    if LibC.shutdown(fd, LibC::SHUT_RD) != 0
+    if @fd_lock.reference { LibC.shutdown(fd, LibC::SHUT_RD) } != 0
       raise ::Socket::Error.from_errno("shutdown read")
     end
   end
 
   private def system_close_write
-    if LibC.shutdown(fd, LibC::SHUT_WR) != 0
+    if @fd_lock.reference { LibC.shutdown(fd, LibC::SHUT_WR) } != 0
       raise ::Socket::Error.from_errno("shutdown write")
     end
   end
@@ -154,7 +157,9 @@ module Crystal::System::Socket
   private def system_setsockopt(optname, optval, level = LibC::SOL_SOCKET)
     optsize = LibC::SocklenT.new(sizeof(typeof(optval)))
 
-    ret = LibC.setsockopt(fd, level, optname, pointerof(optval), optsize)
+    ret = @fd_lock.reference do
+      LibC.setsockopt(fd, level, optname, pointerof(optval), optsize)
+    end
     raise ::Socket::Error.from_errno("setsockopt #{optname}") if ret == -1
     ret
   end
@@ -164,7 +169,9 @@ module Crystal::System::Socket
   end
 
   private def system_blocking=(value)
-    FileDescriptor.set_blocking(fd, value)
+    @fd_lock.reference do
+      FileDescriptor.set_blocking(fd, value)
+    end
   end
 
   def self.get_blocking(fd : Handle)
@@ -176,7 +183,7 @@ module Crystal::System::Socket
   end
 
   private def system_close_on_exec?
-    flags = system_fcntl(LibC::F_GETFD)
+    flags = FileDescriptor.fcntl(fd, LibC::F_GETFD)
     (flags & LibC::FD_CLOEXEC) == LibC::FD_CLOEXEC
   end
 
@@ -190,7 +197,7 @@ module Crystal::System::Socket
   end
 
   private def system_fcntl(cmd, arg = 0)
-    FileDescriptor.fcntl(fd, cmd, arg)
+    @fd_lock.reference { FileDescriptor.fcntl(fd, cmd, arg) }
   end
 
   def self.socketpair(type : ::Socket::Type, protocol : ::Socket::Protocol, blocking : Bool) : {Handle, Handle}
@@ -224,8 +231,10 @@ module Crystal::System::Socket
   end
 
   private def system_close
-    event_loop.before_close(self)
-    event_loop.close(self)
+    if @fd_lock.try_close? { event_loop.before_close(self) }
+      event_loop.close(self)
+      @fd_lock.reset
+    end
   end
 
   def socket_close(&)
@@ -348,4 +357,24 @@ module Crystal::System::Socket
       val
     end
   {% end %}
+
+  private def system_send_to(bytes : Bytes, addr : ::Socket::Address)
+    @fd_lock.write { event_loop.send_to(self, bytes, addr) }
+  end
+
+  private def system_receive_from(bytes : Bytes) : Tuple(Int32, ::Socket::Address)
+    @fd_lock.read { event_loop.receive_from(self, bytes) }
+  end
+
+  private def system_connect(addr, timeout = nil)
+    @fd_lock.write { event_loop.connect(self, addr, timeout) }
+  end
+
+  private def system_read(slice : Bytes) : Int32
+    @fd_lock.read { event_loop.read(self, slice) }
+  end
+
+  private def system_write(slice : Bytes) : Int32
+    @fd_lock.write { event_loop.write(self, slice) }
+  end
 end

src/crystal/system/wasi/socket.cr

@@ -37,6 +37,10 @@ module Crystal::System::Socket
     end
   end
 
+  private def system_accept : {::Socket::Handle, Bool}?
+    event_loop.accept(self)
+  end
+
   private def system_send_buffer_size : Int
     raise NotImplementedError.new "Crystal::System::Socket#system_send_buffer_size"
   end