Messages in this thread | | | Subject | Re: [PATCH 2/6] pstore: Add event tracing support | From | Sai Prakash Ranjan <> | Date | Tue, 18 Sep 2018 01:13:30 +0530 |
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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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