[foreign] RFR 8226250: Calling callback from different native threads causes a VM crash

[Nick Gasson]

Hi Maurizio,

The patch is missing a declaration for p_env in the AArch64
SPECIALIZED_HELPER_BODY macro:

diff --git a/src/hotspot/cpu/aarch64/directUpcallHandler_aarch64.cpp b/src/hotspot/cpu/aarch64/directUpcallHandler_aarch64.cpp
index 913dabd47d..08043b7c86 100644
--- a/src/hotspot/cpu/aarch64/directUpcallHandler_aarch64.cpp
+++ b/src/hotspot/cpu/aarch64/directUpcallHandler_aarch64.cpp
@@ -116,6 +116,7 @@ struct upcall_context {
   int nlongs = (mask & ARG_MASK);                                       \
   int ndoubles = ((mask >> ARG_SHIFT) & ARG_MASK);                      \
   int rettag = RES_TAG;                                                 \
+  void *p_env = NULL;                                                   \
                                                                         \
   JavaCallArguments args((1 + nlongs + ndoubles) * 2);                  \
                                                                         \

With this change, all the tests pass on AArch64.

Thanks,
Nick


> Hi,
> Under JNI, it is user responsibility to attach native threads to the VM
> using attachCurrentThread/detachCurrentThread.
>
> Panama doesn't do this and, as a result, if native code creates a new
> thread and uses it to call a Java callback, an hard crash occurs.
>
> This patch adds a call to AttachCurrentThreadAsDaemon before calling the
> Java callback, only if the native thread has no associated Java thread.
>
> The AttachCurrentThreadAsDaemon allows the VM to be shutdown w/o waiting
> for native threads to complete, which is, I think the semantics we want.
>
> We don't call the dual detach method for two reasons:
>
> * re-attaching the same thread over and over can be expensive
>
> * calling detach after the callback means that we'd lose some register
> values, so we would additional save/restore
>
> Overall, it seems like the 'leak' of JavaThread is not worth the extra
> complexity?
>
> Webrev:
>
> http://cr.openjdk.java.net/~mcimadamore/panama/8226250_v2/
>
> Maurizio