On Tue, 24 May 2022 05:45:17 GMT, Serguei Spitsyn <sspit...@openjdk.org> wrote:
> It was a typo when the original CLEARING_MASK was initially introduced: > > > // Mask to clear normal event bits. > const jlong CLEARING_MASK = (1L >> (TOTAL_MIN_EVENT_TYPE_VAL - > TOTAL_MIN_EVENT_TYPE_VAL)) - 1L; > // Avoid cleaning extension event bits. > jlong enabled_bits = CLEARING_MASK & > env->env_event_enable()->_event_callback_enabled.get_bits(); > > ``` > > The first TOTAL_MIN_EVENT_TYPE_VAL has to be JVMTI_MIN_EVENT_TYPE_VAL as > below: > ` const jlong CLEARING_MASK = (1L >> (JVMTI_MIN_EVENT_TYPE_VAL - > TOTAL_MIN_EVENT_TYPE_VAL)) - 1L;` > > Let me provide some background to understand how this mask is used. > > Normal JVMTI event types are numbered from 50 to 88. There are two constants: > > JVMTI_MIN_EVENT_TYPE_VAL = 50 > JVMTI_MAX_EVENT_TYPE_VAL = 88 > > The extension event types are numbered from 47 to 49. There are also two > constants: > > EXT_MIN_EVENT_TYPE_VAL = 47 > EXT_MAX_EVENT_TYPE_VAL = 49 > > > There are also two additional constants: > > TOTAL_MIN_EVENT_TYPE_VAL = 47 > TOTAL_MAX_EVENT_TYPE_VAL = 88 > > > The `enabled_bits` are shifted left by 47, so that the 0-bit in > `enabled_bits` is for first extension event type. And the first normal JVMTI > event type is numbered 3 in the `enabled_bits` bit mask. The `CLEARING_MASK` > is used to clear only normal JVMTI event types but keep the extension event > bits (0-2) unchanged. > > Testing: > I'll run all JVMTI tests including nsk.jvmti tests and serviceability/jvmti > tests including those added in Loom for virtual thread coverage. This pull request has now been integrated. Changeset: a0cccb54 Author: Serguei Spitsyn <sspit...@openjdk.org> URL: https://git.openjdk.java.net/jdk/commit/a0cccb54791d954bf08da5aac9b9794e370617c8 Stats: 40 lines in 3 files changed: 35 ins; 4 del; 1 mod 8286490: JvmtiEventControllerPrivate::set_event_callbacks CLEARING_MASK computation is incorrect Reviewed-by: jbachorik, lmesnik, amenkov ------------- PR: https://git.openjdk.java.net/jdk/pull/8860
