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

[Sai Prakash Ranjan]

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?

> > +
> > +	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?

Thanks,
Sai

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