# HG changeset patch # User dcubed # Date 1379512930 25200 # Node ID 63147986a4284a0797ffc73ac9aed20c5a6a9631 # Parent 6f45933aef355bc6f4247c49f952074a3e94a09a 8019835: Strings interned in different threads equal but does not == Summary: Add -XX:+VerifyStringTableAtExit option and code to verify StringTable invariants. Reviewed-by: rdurbin, sspitsyn, coleenp diff -r 6f45933aef35 -r 63147986a428 src/share/vm/classfile/javaClasses.cpp --- a/src/share/vm/classfile/javaClasses.cpp Tue Sep 17 20:20:03 2013 +0200 +++ b/src/share/vm/classfile/javaClasses.cpp Wed Sep 18 07:02:10 2013 -0700 @@ -438,6 +438,29 @@ return true; } +bool java_lang_String::equals(oop str1, oop str2) { + assert(str1->klass() == SystemDictionary::String_klass(), + "must be java String"); + assert(str2->klass() == SystemDictionary::String_klass(), + "must be java String"); + typeArrayOop value1 = java_lang_String::value(str1); + int offset1 = java_lang_String::offset(str1); + int length1 = java_lang_String::length(str1); + typeArrayOop value2 = java_lang_String::value(str2); + int offset2 = java_lang_String::offset(str2); + int length2 = java_lang_String::length(str2); + + if (length1 != length2) { + return false; + } + for (int i = 0; i < length1; i++) { + if (value1->char_at(i + offset1) != value2->char_at(i + offset2)) { + return false; + } + } + return true; +} + void java_lang_String::print(Handle java_string, outputStream* st) { oop obj = java_string(); assert(obj->klass() == SystemDictionary::String_klass(), "must be java_string"); diff -r 6f45933aef35 -r 63147986a428 src/share/vm/classfile/javaClasses.hpp --- a/src/share/vm/classfile/javaClasses.hpp Tue Sep 17 20:20:03 2013 +0200 +++ b/src/share/vm/classfile/javaClasses.hpp Wed Sep 18 07:02:10 2013 -0700 @@ -182,6 +182,7 @@ static unsigned int hash_string(oop java_string); static bool equals(oop java_string, jchar* chars, int len); + static bool equals(oop str1, oop str2); // Conversion between '.' and '/' formats static Handle externalize_classname(Handle java_string, TRAPS) { return char_converter(java_string, '/', '.', THREAD); } diff -r 6f45933aef35 -r 63147986a428 src/share/vm/classfile/symbolTable.cpp --- a/src/share/vm/classfile/symbolTable.cpp Tue Sep 17 20:20:03 2013 +0200 +++ b/src/share/vm/classfile/symbolTable.cpp Wed Sep 18 07:02:10 2013 -0700 @@ -807,6 +807,8 @@ } } +// This verification is part of Universe::verify() and needs to be quick. +// See StringTable::verify_and_compare() below for exhaustive verification. void StringTable::verify() { for (int i = 0; i < the_table()->table_size(); ++i) { HashtableEntry* p = the_table()->bucket(i); @@ -825,6 +827,162 @@ the_table()->dump_table(st, "StringTable"); } +StringTable::VerifyRetTypes StringTable::compare_entries( + int bkt1, int e_cnt1, + HashtableEntry* e_ptr1, + int bkt2, int e_cnt2, + HashtableEntry* e_ptr2) { + // These entries are sanity checked by verify_and_compare_entries() + // before this function is called. + oop str1 = e_ptr1->literal(); + oop str2 = e_ptr2->literal(); + + if (str1 == str2) { + tty->print_cr("ERROR: identical oop values (0x" PTR_FORMAT ") " + "in entry @ bucket[%d][%d] and entry @ bucket[%d][%d]", + str1, bkt1, e_cnt1, bkt2, e_cnt2); + return _verify_fail_continue; + } + + if (java_lang_String::equals(str1, str2)) { + tty->print_cr("ERROR: identical String values in entry @ " + "bucket[%d][%d] and entry @ bucket[%d][%d]", + bkt1, e_cnt1, bkt2, e_cnt2); + return _verify_fail_continue; + } + + return _verify_pass; +} + +StringTable::VerifyRetTypes StringTable::verify_entry(int bkt, int e_cnt, + HashtableEntry* e_ptr, + StringTable::VerifyMesgModes mesg_mode) { + + VerifyRetTypes ret = _verify_pass; // be optimistic + + oop str = e_ptr->literal(); + if (str == NULL) { + if (mesg_mode == _verify_with_mesgs) { + tty->print_cr("ERROR: NULL oop value in entry @ bucket[%d][%d]", bkt, + e_cnt); + } + // NULL oop means no more verifications are possible + return _verify_fail_done; + } + + if (str->klass() != SystemDictionary::String_klass()) { + if (mesg_mode == _verify_with_mesgs) { + tty->print_cr("ERROR: oop is not a String in entry @ bucket[%d][%d]", + bkt, e_cnt); + } + // not a String means no more verifications are possible + return _verify_fail_done; + } + + unsigned int h = java_lang_String::hash_string(str); + if (e_ptr->hash() != h) { + if (mesg_mode == _verify_with_mesgs) { + tty->print_cr("ERROR: broken hash value in entry @ bucket[%d][%d], " + "bkt_hash=%d, str_hash=%d", bkt, e_cnt, e_ptr->hash(), h); + } + ret = _verify_fail_continue; + } + + if (the_table()->hash_to_index(h) != bkt) { + if (mesg_mode == _verify_with_mesgs) { + tty->print_cr("ERROR: wrong index value for entry @ bucket[%d][%d], " + "str_hash=%d, hash_to_index=%d", bkt, e_cnt, h, + the_table()->hash_to_index(h)); + } + ret = _verify_fail_continue; + } + + return ret; +} + +// See StringTable::verify() above for the quick verification that is +// part of Universe::verify(). This verification is exhaustive and +// reports on every issue that is found. StringTable::verify() only +// reports on the first issue that is found. +// +// StringTable::verify_entry() checks: +// - oop value != NULL (same as verify()) +// - oop value is a String +// - hash(String) == hash in entry (same as verify()) +// - index for hash == index of entry (same as verify()) +// +// StringTable::compare_entries() checks: +// - oops are unique across all entries +// - String values are unique across all entries +// +int StringTable::verify_and_compare_entries() { + assert(StringTable_lock->is_locked(), "sanity check"); + + int fail_cnt = 0; + + // first, verify all the entries individually: + for (int bkt = 0; bkt < the_table()->table_size(); bkt++) { + HashtableEntry* e_ptr = the_table()->bucket(bkt); + for (int e_cnt = 0; e_ptr != NULL; e_ptr = e_ptr->next(), e_cnt++) { + VerifyRetTypes ret = verify_entry(bkt, e_cnt, e_ptr, _verify_with_mesgs); + if (ret != _verify_pass) { + fail_cnt++; + } + } + } + + // Optimization: if the above check did not find any failures, then + // the comparison loop below does not need to call verify_entry() + // before calling compare_entries(). If there were failures, then we + // have to call verify_entry() to see if the entry can be passed to + // compare_entries() safely. When we call verify_entry() in the loop + // below, we do so quietly to void duplicate messages and we don't + // increment fail_cnt because the failures have already been counted. + bool need_entry_verify = (fail_cnt != 0); + + // second, verify all entries relative to each other: + for (int bkt1 = 0; bkt1 < the_table()->table_size(); bkt1++) { + HashtableEntry* e_ptr1 = the_table()->bucket(bkt1); + for (int e_cnt1 = 0; e_ptr1 != NULL; e_ptr1 = e_ptr1->next(), e_cnt1++) { + if (need_entry_verify) { + VerifyRetTypes ret = verify_entry(bkt1, e_cnt1, e_ptr1, + _verify_quietly); + if (ret == _verify_fail_done) { + // cannot use the current entry to compare against other entries + continue; + } + } + + for (int bkt2 = bkt1; bkt2 < the_table()->table_size(); bkt2++) { + HashtableEntry* e_ptr2 = the_table()->bucket(bkt2); + int e_cnt2; + for (e_cnt2 = 0; e_ptr2 != NULL; e_ptr2 = e_ptr2->next(), e_cnt2++) { + if (bkt1 == bkt2 && e_cnt2 <= e_cnt1) { + // skip the entries up to and including the one that + // we're comparing against + continue; + } + + if (need_entry_verify) { + VerifyRetTypes ret = verify_entry(bkt2, e_cnt2, e_ptr2, + _verify_quietly); + if (ret == _verify_fail_done) { + // cannot compare against this entry + continue; + } + } + + // compare two entries, report and count any failures: + if (compare_entries(bkt1, e_cnt1, e_ptr1, bkt2, e_cnt2, e_ptr2) + != _verify_pass) { + fail_cnt++; + } + } + } + } + } + return fail_cnt; +} // Create a new table and using alternate hash code, populate the new table // with the existing strings. Set flag to use the alternate hash code afterwards. diff -r 6f45933aef35 -r 63147986a428 src/share/vm/classfile/symbolTable.hpp --- a/src/share/vm/classfile/symbolTable.hpp Tue Sep 17 20:20:03 2013 +0200 +++ b/src/share/vm/classfile/symbolTable.hpp Wed Sep 18 07:02:10 2013 -0700 @@ -311,6 +311,26 @@ static void verify(); static void dump(outputStream* st); + enum VerifyMesgModes { + _verify_quietly = 0, + _verify_with_mesgs = 1 + }; + + enum VerifyRetTypes { + _verify_pass = 0, + _verify_fail_continue = 1, + _verify_fail_done = 2 + }; + + static VerifyRetTypes compare_entries(int bkt1, int e_cnt1, + HashtableEntry* e_ptr1, + int bkt2, int e_cnt2, + HashtableEntry* e_ptr2); + static VerifyRetTypes verify_entry(int bkt, int e_cnt, + HashtableEntry* e_ptr, + VerifyMesgModes mesg_mode); + static int verify_and_compare_entries(); + // Sharing static void copy_buckets(char** top, char*end) { the_table()->Hashtable::copy_buckets(top, end); diff -r 6f45933aef35 -r 63147986a428 src/share/vm/runtime/globals.hpp --- a/src/share/vm/runtime/globals.hpp Tue Sep 17 20:20:03 2013 +0200 +++ b/src/share/vm/runtime/globals.hpp Wed Sep 18 07:02:10 2013 -0700 @@ -2525,6 +2525,9 @@ product(bool, PrintStringTableStatistics, false, \ "print statistics about the StringTable and SymbolTable") \ \ + diagnostic(bool, VerifyStringTableAtExit, false, \ + "verify StringTable contents at exit") \ + \ notproduct(bool, PrintSymbolTableSizeHistogram, false, \ "print histogram of the symbol table") \ \ diff -r 6f45933aef35 -r 63147986a428 src/share/vm/runtime/java.cpp --- a/src/share/vm/runtime/java.cpp Tue Sep 17 20:20:03 2013 +0200 +++ b/src/share/vm/runtime/java.cpp Wed Sep 18 07:02:10 2013 -0700 @@ -544,6 +544,19 @@ // it will run into trouble when system destroys static variables. MemTracker::shutdown(MemTracker::NMT_normal); + if (VerifyStringTableAtExit) { + int fail_cnt = 0; + { + MutexLocker ml(StringTable_lock); + fail_cnt = StringTable::verify_and_compare_entries(); + } + + if (fail_cnt != 0) { + tty->print_cr("ERROR: fail_cnt=%d", fail_cnt); + guarantee(fail_cnt == 0, "unexpected StringTable verification failures"); + } + } + #undef BEFORE_EXIT_NOT_RUN #undef BEFORE_EXIT_RUNNING #undef BEFORE_EXIT_DONE