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8035663: Suspicious failure of test java/util/concurrent/Phaser/FickleRegister.java

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Reviewed-by: shade, coleenp
This commit is contained in:
David Holmes 2014-11-25 21:00:21 -05:00
parent 5ffd65a731
commit 26dc1466b7
3 changed files with 50 additions and 11 deletions
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50
hotspot/src/share/vm/prims/unsafe.cpp
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@ -262,10 +262,33 @@ UNSAFE_ENTRY(void, Unsafe_SetObjectVolatile(JNIEnv *env, jobject unsafe, jobject
UNSAFE_END
#ifndef SUPPORTS_NATIVE_CX8
// Keep old code for platforms which may not have atomic jlong (8 bytes) instructions
// Volatile long versions must use locks if !VM_Version::supports_cx8().
// support_cx8 is a surrogate for 'supports atomic long memory ops'.
// VM_Version::supports_cx8() is a surrogate for 'supports atomic long memory ops'.
//
// On platforms which do not support atomic compare-and-swap of jlong (8 byte)
// values we have to use a lock-based scheme to enforce atomicity. This has to be
// applied to all Unsafe operations that set the value of a jlong field. Even so
// the compareAndSwapLong operation will not be atomic with respect to direct stores
// to the field from Java code. It is important therefore that any Java code that
// utilizes these Unsafe jlong operations does not perform direct stores. To permit
// direct loads of the field from Java code we must also use Atomic::store within the
// locked regions. And for good measure, in case there are direct stores, we also
// employ Atomic::load within those regions. Note that the field in question must be
// volatile and so must have atomic load/store accesses applied at the Java level.
//
// The locking scheme could utilize a range of strategies for controlling the locking
// granularity: from a lock per-field through to a single global lock. The latter is
// the simplest and is used for the current implementation. Note that the Java object
// that contains the field, can not, in general, be used for locking. To do so can lead
// to deadlocks as we may introduce locking into what appears to the Java code to be a
// lock-free path.
//
// As all the locked-regions are very short and themselves non-blocking we can treat
// them as leaf routines and elide safepoint checks (ie we don't perform any thread
// state transitions even when blocking for the lock). Note that if we do choose to
// add safepoint checks and thread state transitions, we must ensure that we calculate
// the address of the field _after_ we have acquired the lock, else the object may have
// been moved by the GC
UNSAFE_ENTRY(jlong, Unsafe_GetLongVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset))
UnsafeWrapper("Unsafe_GetLongVolatile");
@ -277,8 +300,8 @@ UNSAFE_ENTRY(jlong, Unsafe_GetLongVolatile(JNIEnv *env, jobject unsafe, jobject
else {
Handle p (THREAD, JNIHandles::resolve(obj));
jlong* addr = (jlong*)(index_oop_from_field_offset_long(p(), offset));
ObjectLocker ol(p, THREAD);
jlong value = *addr;
MutexLockerEx mu(UnsafeJlong_lock, Mutex::_no_safepoint_check_flag);
jlong value = Atomic::load(addr);
return value;
}
}
@ -293,8 +316,8 @@ UNSAFE_ENTRY(void, Unsafe_SetLongVolatile(JNIEnv *env, jobject unsafe, jobject o
else {
Handle p (THREAD, JNIHandles::resolve(obj));
jlong* addr = (jlong*)(index_oop_from_field_offset_long(p(), offset));
ObjectLocker ol(p, THREAD);
*addr = x;
MutexLockerEx mu(UnsafeJlong_lock, Mutex::_no_safepoint_check_flag);
Atomic::store(x, addr);
}
}
UNSAFE_END
@ -403,8 +426,8 @@ UNSAFE_ENTRY(void, Unsafe_SetOrderedLong(JNIEnv *env, jobject unsafe, jobject ob
else {
Handle p (THREAD, JNIHandles::resolve(obj));
jlong* addr = (jlong*)(index_oop_from_field_offset_long(p(), offset));
ObjectLocker ol(p, THREAD);
*addr = x;
MutexLockerEx mu(UnsafeJlong_lock, Mutex::_no_safepoint_check_flag);
Atomic::store(x, addr);
}
}
#endif
@ -1152,14 +1175,19 @@ UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSwapLong(JNIEnv *env, jobject unsafe, jo
UnsafeWrapper("Unsafe_CompareAndSwapLong");
Handle p (THREAD, JNIHandles::resolve(obj));
jlong* addr = (jlong*)(index_oop_from_field_offset_long(p(), offset));
#ifdef SUPPORTS_NATIVE_CX8
return (jlong)(Atomic::cmpxchg(x, addr, e)) == e;
#else
if (VM_Version::supports_cx8())
return (jlong)(Atomic::cmpxchg(x, addr, e)) == e;
else {
jboolean success = false;
ObjectLocker ol(p, THREAD);
if (*addr == e) { *addr = x; success = true; }
MutexLockerEx mu(UnsafeJlong_lock, Mutex::_no_safepoint_check_flag);
jlong val = Atomic::load(addr);
if (val == e) { Atomic::store(x, addr); success = true; }
return success;
}
#endif
UNSAFE_END
UNSAFE_ENTRY(void, Unsafe_Park(JNIEnv *env, jobject unsafe, jboolean isAbsolute, jlong time))