Re: [PATCH v3 0/9] trace_uprobe: Support SDT markers having reference count (semaphore)

[Oleg Nesterov <oleg@redhat.com>]

Sorry Ravi, I saved the new version for review and forgot about it... I'll
try to do this on weekend.

On 05/03, Ravi Bangoria wrote:
> 
> On 04/17/2018 10:02 AM, Ravi Bangoria wrote:
> > Userspace Statically Defined Tracepoints[1] are dtrace style markers
> > inside userspace applications. Applications like PostgreSQL, MySQL,
> > Pthread, Perl, Python, Java, Ruby, Node.js, libvirt, QEMU, glib etc
> > have these markers embedded in them. These markers are added by developer
> > at important places in the code. Each marker source expands to a single
> > nop instruction in the compiled code but there may be additional
> > overhead for computing the marker arguments which expands to couple of
> > instructions. In case the overhead is more, execution of it can be
> > omitted by runtime if() condition when no one is tracing on the marker:
> >
> >     if (reference_counter > 0) {
> >         Execute marker instructions;
> >     }   
> >
> > Default value of reference counter is 0. Tracer has to increment the 
> > reference counter before tracing on a marker and decrement it when
> > done with the tracing.
> 
> Hi Oleg, Masami,
> 
> Can you please review this :) ?
> 
> Thanks.
>