8268165: AsyncLogging will crash if rotate() fails

LogFileOutput::rotate() may leave _stream NULL because os::fopen() may return NULL due to space or inode limitations.  AsyncLogWriter::write() calls LogFileOutput::write_blocking() without null check.  Null check is added to prevent from crashing.

Reviewed-by: ysuenaga

src/hotspot/share/logging/logFileOutput.cpp

@@ -285,8 +285,26 @@ bool LogFileOutput::initialize(const char* options, outputStream* errstream) {
   return true;
 }
 
+class RotationLocker : public StackObj {
+  Semaphore& _sem;
+
+ public:
+  RotationLocker(Semaphore& sem) : _sem(sem) {
+    sem.wait();
+  }
+
+  ~RotationLocker() {
+    _sem.signal();
+  }
+};
+
 int LogFileOutput::write_blocking(const LogDecorations& decorations, const char* msg) {
-  _rotation_semaphore.wait();
+  RotationLocker lock(_rotation_semaphore);
+  if (_stream == NULL) {
+    // An error has occurred with this output, avoid writing to it.
+    return 0;
+  }
+
   int written = LogFileStreamOutput::write(decorations, msg);
   if (written > 0) {
     _current_size += written;
@@ -295,7 +313,6 @@ int LogFileOutput::write_blocking(const LogDecorations& decorations, const char*
       rotate();
     }
   }
-  _rotation_semaphore.signal();
 
   return written;
 }
@@ -327,7 +344,7 @@ int LogFileOutput::write(LogMessageBuffer::Iterator msg_iterator) {
     return 0;
   }
 
-  _rotation_semaphore.wait();
+  RotationLocker lock(_rotation_semaphore);
   int written = LogFileStreamOutput::write(msg_iterator);
   if (written > 0) {
     _current_size += written;
@@ -336,7 +353,6 @@ int LogFileOutput::write(LogMessageBuffer::Iterator msg_iterator) {
       rotate();
     }
   }
-  _rotation_semaphore.signal();
 
   return written;
 }
@@ -363,13 +379,12 @@ void LogFileOutput::force_rotate() {
     // Rotation not possible
     return;
   }
-  _rotation_semaphore.wait();
+
+  RotationLocker lock(_rotation_semaphore);
   rotate();
-  _rotation_semaphore.signal();
 }
 
 void LogFileOutput::rotate() {
-
   if (fclose(_stream)) {
     jio_fprintf(defaultStream::error_stream(), "Error closing file '%s' during log rotation (%s).\n",
                 _file_name, os::strerror(errno));