Messages in this thread | ![/](/images/icornerl.gif) | | Date | Sat, 29 Aug 2020 23:52:32 +0800 | From | Wen Gong <> | Subject | Re: [for-next][PATCH 2/2] tracing: Use temp buffer when filtering events |
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On 2020-08-29 06:55, Steven Rostedt wrote: > 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 Thanks Steve!
If change like this, I think it will fix my issue of crash. Will you commit this change? > >> trace_event_setup(entry, type, flags, pc); >> entry->array[0] = len; >> return entry;
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