Messages in this thread | | | Date | Fri, 28 Aug 2020 18:55:38 -0400 | From | Steven Rostedt <> | Subject | Re: [for-next][PATCH 2/2] tracing: Use temp buffer when filtering events |
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On Fri, 28 Aug 2020 18:54:50 -0400 Steven Rostedt <rostedt@goodmis.org> wrote:
> On Fri, 28 Aug 2020 18:49:55 -0400 > Steven Rostedt <rostedt@goodmis.org> wrote: > > > On Fri, 28 Aug 2020 15:53:06 +0800 > > Wen Gong <wgong@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;
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