On 9/9/2018 1:57 AM, Sai Prakash Ranjan wrote:

quoted

+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;
+