On 22/11/2023 3:09 am, Vladimir Kozlov wrote:
CCing to serviceability group.
Do we still support dtrace?
A qualified "yes" - the hooks still exist, mainly for systemTap IIRC but
we don't actively update or maintain anything so I expect there is some
bitrot.
Thanks,
Vladimir K
On 11/21/23 4:34 AM, Thomas Stüfe wrote:
Hi,
It seems that the handling of DTraceMethodProbes is inconsistent: in
most places, we handle the flag at runtime by generating code that
uses conditional jumps. In one place (C1), we don't. There, generation
is conditional on DTraceMethodProbes at compile time.
Yeah this code in C1 seems wrong:
// Change in DTrace flags may invalidate compilation.
if (!failing() &&
( (!dtrace_method_probes() && DTraceMethodProbes) ||
(!dtrace_alloc_probes() && DTraceAllocProbes) )) {
record_failure("DTrace flags change invalidated dependencies");
}
The flag can't change dynamically. Maybe once upon a time it could ?
David
-----
The former looks like it is possible for the value
of DTraceMethodProbes to change at runtime, and that generated code
should be able to react seamlessly. However, DTraceMethodProbes is not
a manageable flag.
Which side is right? Do we need to emit conditional jumps, but if so,
why not in C1?
Thanks, Thomas
