Quoting Sai Prakash Ranjan (2018-09-11 03:46:01)
> On 9/9/2018 1:57 AM, Sai Prakash Ranjan wrote:
> > +void notrace pstore_event_call(struct trace_event_buffer *fbuffer)
> > +{
> > + struct trace_iterator *iter;
> > + struct trace_seq *s;
> > + struct trace_event_call *event_call;
> > + struct pstore_record record;
> > + struct trace_event *event;
> > + struct seq_buf *seq;
> > + unsigned long flags;
> > +
> > + if (!psinfo)
> > + return;
> > +
> > + if (unlikely(oops_in_progress))
> > + return;
> > +
> > + pstore_record_init(&record, psinfo);
> > + record.type = PSTORE_TYPE_EVENT;
> > +
> > + iter = kmalloc(sizeof(*iter), GFP_KERNEL);
> > + if (!iter)
> > + return;
> > +
> > + 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;
> > + event_call->event.funcs->trace(iter, 0, event);
> > + 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);
> > +
> > +fail_event:
> > + kfree(iter);
> > +}
> > +
> >
>
> When tracing sched events on sdm845 mtp, I hit below bug repeatedly.
> Seems like pstore_event_call can be called in atomic context.
> I will respin the below fix in next version of the patch.
> Reviews on other parts would be appreciated, thanks.
>
> diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c
> index d47dc93ac098..a497cf782ee8 100644
> --- a/fs/pstore/ftrace.c
> +++ b/fs/pstore/ftrace.c
> @@ -73,6 +73,7 @@ void notrace pstore_event_call(struct
> trace_event_buffer *fbuffer)
> struct trace_event *event;
> struct seq_buf *seq;
> unsigned long flags;
> + gfp_t gfpflags;
>
> if (!psinfo)
> return;
> @@ -83,7 +84,9 @@ void notrace pstore_event_call(struct
> trace_event_buffer *fbuffer)
> pstore_record_init(&record, psinfo);
> record.type = PSTORE_TYPE_EVENT;
>
> - iter = kmalloc(sizeof(*iter), GFP_KERNEL);
> + gfpflags = (in_atomic() || irqs_disabled()) ? GFP_ATOMIC :
> GFP_KERNEL;
> +
Do you need to allocate at all? Can you throw the iter on the stack?
Using in_atomic() and irqs_disabled() to figure out if an atomic or a
non-atomic allocation should be used is not a good solution.
