[PATCH] ath10k: change len of trace_ath10k_log_dbg_dump for large buffer size

[Steven Rostedt]

On Wed, 10 Feb 2021 10:01:57 +0800
Wen Gong <wgong at codeaurora.org> wrote:

> Not tested with latest kernel.
> The reason is below which I said in 
> https://lore.kernel.org/lkml/b504b3d7e989cae108669a0cd3072454@codeaurora.org/
> 
> 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.

Yeah, looking at this, I do see that this is a bug upstream.

Can you test this patch?

-- Steve


diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b79bcacdd6f9..a0b352aa23fe 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2739,7 +2739,7 @@ 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 (len < PAGE_SIZE && val == 1) {
 			trace_event_setup(entry, type, trace_ctx);
 			entry->array[0] = len;
 			return entry;