721 
 722 // rotate_log must be called from VMThread at safepoint. In case need change parameters
 723 // for gc log rotation from thread other than VMThread, a sub type of VM_Operation
 724 // should be created and be submitted to VMThread's operation queue. DO NOT call this
 725 // function directly. Currently, it is safe to rotate log at safepoint through VMThread.
 726 // That is, no mutator threads and concurrent GC threads run parallel with VMThread to
 727 // write to gc log file at safepoint. If in future, changes made for mutator threads or
 728 // concurrent GC threads to run parallel with VMThread at safepoint, write and rotate_log
 729 // must be synchronized.
 730 void gcLogFileStream::rotate_log(bool force, outputStream* out) {
 731   char time_msg[O_BUFLEN];
 732   char time_str[EXTRACHARLEN];
 733   char current_file_name[JVM_MAXPATHLEN];
 734   char renamed_file_name[JVM_MAXPATHLEN];
 735 
 736   if (!should_rotate(force)) {
 737     return;
 738   }
 739 
 740 #ifdef ASSERT
 741   Thread *thread = Thread::current();
 742   assert(thread == NULL ||
 743          (thread->is_VM_thread() && SafepointSynchronize::is_at_safepoint()),
 744          "Must be VMThread at safepoint");
 745 #endif
 746   if (NumberOfGCLogFiles == 1) {
 747     // rotate in same file
 748     rewind();
 749     _bytes_written = 0L;
 750     jio_snprintf(time_msg, sizeof(time_msg), "File  %s rotated at %s\n",
 751                  _file_name, os::local_time_string((char *)time_str, sizeof(time_str)));
 752     write(time_msg, strlen(time_msg));
 753 
 754     if (out != NULL) {
 755       out->print("%s", time_msg);
 756     }
 757 
 758     dump_loggc_header();
 759     return;
 760   }
 761 

1041     _outer_xmlStream = NULL;
1042 
1043     if (file) {
1044       file->flush();
1045 
1046       // Can't delete or close the file because delete and fclose aren't
1047       // async-safe. We are about to die, so leave it to the kernel.
1048       // delete file;
1049     }
1050   }
1051 }
1052 
1053 intx defaultStream::hold(intx writer_id) {
1054   bool has_log = has_log_file();  // check before locking
1055   if (// impossible, but who knows?
1056       writer_id == NO_WRITER ||
1057 
1058       // bootstrap problem
1059       tty_lock == NULL ||
1060 
1061       // can't grab a lock or call Thread::current() if TLS isn't initialized
1062       ThreadLocalStorage::thread() == NULL ||
1063 
1064       // developer hook
1065       !SerializeVMOutput ||
1066 
1067       // VM already unhealthy
1068       is_error_reported() ||
1069 
1070       // safepoint == global lock (for VM only)
1071       (SafepointSynchronize::is_synchronizing() &&
1072        Thread::current()->is_VM_thread())
1073       ) {
1074     // do not attempt to lock unless we know the thread and the VM is healthy
1075     return NO_WRITER;
1076   }
1077   if (_writer == writer_id) {
1078     // already held, no need to re-grab the lock
1079     return NO_WRITER;
1080   }
1081   tty_lock->lock_without_safepoint_check();
1082   // got the lock

 721 
 722 // rotate_log must be called from VMThread at safepoint. In case need change parameters
 723 // for gc log rotation from thread other than VMThread, a sub type of VM_Operation
 724 // should be created and be submitted to VMThread's operation queue. DO NOT call this
 725 // function directly. Currently, it is safe to rotate log at safepoint through VMThread.
 726 // That is, no mutator threads and concurrent GC threads run parallel with VMThread to
 727 // write to gc log file at safepoint. If in future, changes made for mutator threads or
 728 // concurrent GC threads to run parallel with VMThread at safepoint, write and rotate_log
 729 // must be synchronized.
 730 void gcLogFileStream::rotate_log(bool force, outputStream* out) {
 731   char time_msg[O_BUFLEN];
 732   char time_str[EXTRACHARLEN];
 733   char current_file_name[JVM_MAXPATHLEN];
 734   char renamed_file_name[JVM_MAXPATHLEN];
 735 
 736   if (!should_rotate(force)) {
 737     return;
 738   }
 739 
 740 #ifdef ASSERT
 741   Thread *thread = Thread::current_or_null();
 742   assert(thread == NULL ||
 743          (thread->is_VM_thread() && SafepointSynchronize::is_at_safepoint()),
 744          "Must be VMThread at safepoint");
 745 #endif
 746   if (NumberOfGCLogFiles == 1) {
 747     // rotate in same file
 748     rewind();
 749     _bytes_written = 0L;
 750     jio_snprintf(time_msg, sizeof(time_msg), "File  %s rotated at %s\n",
 751                  _file_name, os::local_time_string((char *)time_str, sizeof(time_str)));
 752     write(time_msg, strlen(time_msg));
 753 
 754     if (out != NULL) {
 755       out->print("%s", time_msg);
 756     }
 757 
 758     dump_loggc_header();
 759     return;
 760   }
 761 

1041     _outer_xmlStream = NULL;
1042 
1043     if (file) {
1044       file->flush();
1045 
1046       // Can't delete or close the file because delete and fclose aren't
1047       // async-safe. We are about to die, so leave it to the kernel.
1048       // delete file;
1049     }
1050   }
1051 }
1052 
1053 intx defaultStream::hold(intx writer_id) {
1054   bool has_log = has_log_file();  // check before locking
1055   if (// impossible, but who knows?
1056       writer_id == NO_WRITER ||
1057 
1058       // bootstrap problem
1059       tty_lock == NULL ||
1060 
1061       // can't grab a lock if current Thread isn't set
1062       Thread::current_or_null() == NULL ||
1063 
1064       // developer hook
1065       !SerializeVMOutput ||
1066 
1067       // VM already unhealthy
1068       is_error_reported() ||
1069 
1070       // safepoint == global lock (for VM only)
1071       (SafepointSynchronize::is_synchronizing() &&
1072        Thread::current()->is_VM_thread())
1073       ) {
1074     // do not attempt to lock unless we know the thread and the VM is healthy
1075     return NO_WRITER;
1076   }
1077   if (_writer == writer_id) {
1078     // already held, no need to re-grab the lock
1079     return NO_WRITER;
1080   }
1081   tty_lock->lock_without_safepoint_check();
1082   // got the lock