On Mon, Mar 30, 2015 at 10:07:08AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Mon, Mar 30, 2015 at 02:56:31PM +0200, Jiri Olsa escreveu:
> > On Mon, Mar 30, 2015 at 09:48:52PM +0900, Namhyung Kim wrote:
> > > Hi Jiri,
> > >
> > > On Mon, Mar 30, 2015 at 01:49:07PM +0200, Jiri Olsa wrote:
> > > > On Mon, Mar 30, 2015 at 01:21:08PM +0200, Jiri Olsa wrote:
> > > > > On Mon, Mar 30, 2015 at 12:22:20PM +0200, Jiri Olsa wrote:
> > > > > > On Mon, Mar 30, 2015 at 10:07:37AM +0200, Jiri Olsa wrote:
> > > > - th = thread__new(pid, tid);
> > > > + th = thread__new(machine, pid, tid);
> > > > if (th != NULL) {
> > > > +
> > > > + pthread_mutex_lock(&machine->threads_lock);
> > > > rb_link_node(&th->rb_node, parent, p);
> > > > rb_insert_color(&th->rb_node, &machine->threads);
> > > > + pthread_mutex_unlock(&machine->threads_lock);
> > >
> > > I think you also need to protect the rb tree traversal above.
> >
> > yep, I already have another version.. but it blows on another place ;-)
>
> Well, why? The point of refcounting is that the structure will not go
> away while we have it in the rbtree.
>
> Or are you talking about two threads trying to insert entries in the
> rbtree? Can you point where this can happen?
yep, as I wrote in previous email:
> looks like race among __machine__findnew_thread and thread__put
> over the machine->threads rb_tree insert/removal
update thread:
perf_event__process_sample
perf_event__preprocess_sample
machine__findnew_thread
traverse machine->threads
display thread:
perf_top__sort_new_samples
hists__delete_entries
...
hist_entry__delete(struct hist_entry *he)
thread__zput(he->thread);
>
> > > But this makes every sample processing grabs and releases the lock so
> > > might cause high overhead. It can be a problem if such processing is
> > > done parallelly like my multi-thread work. :-/
>
> > yep.. perhaps instead of more locking we need to find a way where
> > only single thread do the update on hists/threads
>
> But that should be really rare, no? The problem is to search in one
> thread (the fast path) and inserting entries (slow path), no?
there're many new threads on kernel make -j25 workload ;-)
jirka
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