On Fri, 28 Aug 2020 18:54:50 -0400
Steven Rostedt <rost...@goodmis.org> wrote:
> On Fri, 28 Aug 2020 18:49:55 -0400
> Steven Rostedt <rost...@goodmis.org> wrote:
>
> > On Fri, 28 Aug 2020 15:53:06 +0800
> > Wen Gong <wg...@codeaurora.org> wrote:
> >
> > > this patch commit id is : 0fc1b09ff1ff404ddf753f5ffa5cd0adc8fdcdc9 which
> > > has upstream.
> > >
> > > how much size is the per cpu buffer?
> > > seems it is initilized in trace_buffered_event_enable,
> > > it is only 1 page size as below:
> > > void trace_buffered_event_enable(void)
> > > {
> > > ...
> > > for_each_tracing_cpu(cpu) {
> > > page = alloc_pages_node(cpu_to_node(cpu),
> > > GFP_KERNEL | __GFP_NORETRY, 0);
> > > If the size of buffer to trace is more than 1 page, such as 46680, then
> > > it trigger kernel crash/panic in my case while run trace-cmd.
> > > After debugging, the trace_file->flags in
> > > trace_event_buffer_lock_reserve is 0x40b while run trace-cmd, and it is
> > > 0x403 while collecting ftrace log.
> > >
> > > Is it have any operation to disable this patch dynamically?
> >
> > It shouldn't be disabled, this is a bug that needs to be fixed.
> >
> > Also, if an event is more than a page, it wont be saved in the ftrace
> > ring buffer, as events are limited by page size minus the headers.
> >
>
> Untested (not even compiled, as I'm now on PTO) but does this patch
> work for you?
>
> -- Steve
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index f40d850ebabc..3a9b4422e7fc 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -2598,7 +2598,7 @@ trace_event_buffer_lock_reserve(struct trace_buffer
> **current_rb,
> (entry = this_cpu_read(trace_buffered_event))) {
> /* Try to use the per cpu buffer first */
> val = this_cpu_inc_return(trace_buffered_event_cnt);
> - if (val == 1) {
> + if (val == 1 || (len > (PAGE_SIZE - 8))) {
That was suppose to be:
if (val == 1 && (len < (PAGE_SIZE - 8))) {
-- Steve
> trace_event_setup(entry, type, flags, pc);
> entry->array[0] = len;
> return entry;
