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8252529: Unsafe Documentation around Barrier Methods Inaccurate

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Reviewed-by: psandoz
This commit is contained in:
Ian Graves 2020-09-01 13:43:26 -07:00
parent b3e264187a
commit de49337060
1 changed files with 15 additions and 6 deletions
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21
src/java.base/share/classes/jdk/internal/misc/Unsafe.java
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@ -3412,9 +3412,8 @@ public final class Unsafe {
* Corresponds to C11 atomic_thread_fence(memory_order_acquire) * Corresponds to C11 atomic_thread_fence(memory_order_acquire)
* (an "acquire fence"). * (an "acquire fence").
* *
* A pure LoadLoad fence is not provided, since the addition of LoadStore * Provides a LoadLoad barrier followed by a LoadStore barrier.
* is almost always desired, and most current hardware instructions that *
* provide a LoadLoad barrier also provide a LoadStore barrier for free.
* @since 1.8 * @since 1.8
*/ */
@HotSpotIntrinsicCandidate @HotSpotIntrinsicCandidate
@ -3427,9 +3426,9 @@ public final class Unsafe {
* Corresponds to C11 atomic_thread_fence(memory_order_release) * Corresponds to C11 atomic_thread_fence(memory_order_release)
* (a "release fence"). * (a "release fence").
* *
* A pure StoreStore fence is not provided, since the addition of LoadStore * Provides a StoreStore barrier followed by a LoadStore barrier.
* is almost always desired, and most current hardware instructions that *
* provide a StoreStore barrier also provide a LoadStore barrier for free. *
* @since 1.8 * @since 1.8
*/ */
@HotSpotIntrinsicCandidate @HotSpotIntrinsicCandidate
@ -3450,6 +3449,11 @@ public final class Unsafe {
/** /**
* Ensures that loads before the fence will not be reordered with * Ensures that loads before the fence will not be reordered with
* loads after the fence. * loads after the fence.
*
* @implNote
* This method is operationally equivalent to {@link #loadFence()}.
*
* @since 9
*/ */
public final void loadLoadFence() { public final void loadLoadFence() {
loadFence(); loadFence();
@ -3458,6 +3462,11 @@ public final class Unsafe {
/** /**
* Ensures that stores before the fence will not be reordered with * Ensures that stores before the fence will not be reordered with
* stores after the fence. * stores after the fence.
*
* @implNote
* This method is operationally equivalent to {@link #storeFence()}.
*
* @since 9
*/ */
public final void storeStoreFence() { public final void storeStoreFence() {
storeFence(); storeFence();