Re: [PATCH 2/6] pstore: Add event tracing support

[Sai Prakash Ranjan]

On 9/19/2018 2:14 AM, Steven Rostedt wrote:
> On Tue, 18 Sep 2018 23:22:48 +0530
> Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx> wrote:
>
> > On 9/18/2018 5:04 AM, Steven Rostedt wrote:
> > > It looks like pstore_event_call() gets called from a trace event. You
> > > can't call kmalloc() from one. One thing is that kmalloc has
> > > tracepoints itself. You trace those you just entered an infinite loop.
> > >
> > >    
> >
> > Ok will remove it in v2. But any alternative way to do this?
>
> I think I describe it below.

Ok got it, will change and post the 2nd version soon.

> > > > +
> > > > +	event_call = fbuffer->trace_file->event_call;
> > > > +	if (!event_call || !event_call->event.funcs ||
> > > > +	    !event_call->event.funcs->trace)
> > > > +		goto fail_event;
> > > > +
> > > > +	event = &fbuffer->trace_file->event_call->event;
> > > > +
> > > > +	spin_lock_irqsave(&psinfo->buf_lock, flags);
> > > > +
> > > > +	trace_seq_init(&iter->seq);
> > > > +	iter->ent = fbuffer->entry;
> > >
> > > I guess what you are doing is needing to translate the raw data into
> > > ascii output, and need the trace_iterator to do so.
> > >
> > > You are already under a psinfo->buf_lock. Add a dummy iterator to that
> > > and use it instead.
> > >
> > > 	trace_seq_init(&psinfo->iter->seq);
> > >    
> > > > +	event_call->event.funcs->trace(iter, 0, event);
> > >
> > > 				      (psinfo->iter, 0 , event);
> > >
> > > etc.
> > >    
> >
> > Sure, will update in v2.
> >
> > > > +	trace_seq_putc(&iter->seq, 0);
> > > > +
> > > > +	if (seq->size > psinfo->bufsize)
> > > > +		seq->size = psinfo->bufsize;
> > > > +
> > > > +	s = &iter->seq;
> > > > +	seq = &s->seq;
> > > > +
> > > > +	record.buf = (char *)(seq->buffer);
> > > > +	record.size = seq->len;
> > > > +	psinfo->write(&record);
> > > > +
> > > > +	spin_unlock_irqrestore(&psinfo->buf_lock, flags);
> > >
> > > You may also need to convert these spin_locks into raw_spin_locks as
> > > when PREEMPT_RT enters the kernel you don't want them to turn into
> > > mutexes.
> > >
> > > But that can be another patch.
> > >    
> >
> > I will change this in v2, but can't we have it in same patch?
>
> I suggested a separate patch because buf_lock is used elsewhere.
> Changing it to "raw_spin_lock" will affect more than just what this
> patch series does. Thus, I recommend making it a separate patch to keep
> this patch series from being more intrusive than it needs to be.

Sure, thanks a lot.

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