RFR: 8304725: AsyncGetCallTrace can cause SIGBUS on M1 [v4]

[David Holmes]

On Fri, 24 Mar 2023 10:35:36 GMT, Johannes Bechberger <jbechberger at openjdk.org> wrote:

>> Fixes the issue by transitioning the thread into the WXWrite mode while walking the stack in AsyncGetCallTrace.
>> 
>> Tested on my M1 mac.
>
> Johannes Bechberger has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Remove misc lines
>  - Disable caching in ASGCT

Changes requested by dholmes (Reviewer).

src/hotspot/share/runtime/thread.hpp line 641:

> 639:   void set_in_asgct(bool value) { _in_asgct = value; }
> 640:   static bool current_in_asgct() {
> 641:     Thread *cur = Thread::current();

You need to use`current_or_null_safe` here as you may be in a signal handling context.

src/hotspot/share/runtime/thread.hpp line 651:

> 649:  public:
> 650:   ThreadInAsgct(Thread* thread) : _thread(thread) {
> 651:     assert(thread != NULL, "invariant");

s/NULL/nullptr/

-------------

PR Review: https://git.openjdk.org/jdk/pull/13144#pullrequestreview-1360181938
PR Review Comment: https://git.openjdk.org/jdk/pull/13144#discussion_r1150010290
PR Review Comment: https://git.openjdk.org/jdk/pull/13144#discussion_r1150010653