On 9/17/2018 11:08 PM, Stephen Boyd wrote:
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;
+
Hi Stephen
Thanks for the comments.
Do you need to allocate at all? Can you throw the iter on the stack?
Yes since we need to copy the contents to pstore buffer.
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.
I took reference from a similar use by graph_trace_open() which can be
called in atomic context via ftrace_dump(). I am open to correct this if
there is some other way.
Sai
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