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authorDaniel Thompson <daniel.thompson@linaro.org>2014-11-06 12:41:56 +0000
committerSteven Rostedt <rostedt@goodmis.org>2014-11-13 21:27:25 -0500
commit8520dedbbf7578a397ecdfcf6ab83f775f914cfe (patch)
treefd60f0d3d8775a623ad5ac31042cd8ae4ba337c0 /kernel/trace
parentc270cc75cd22b606c901e606fbb93b002c2a655f (diff)
tracing: kdb: Fix kernel livelock with empty buffers
Currently kdb's ftdump command will livelock by constantly printk'ing the empty string at KERN_EMERG level if it run when the ftrace system is not in use. This occurs because trace_empty() never returns false when the ring buffers are left at the start of a non-consuming read [launched by ring_buffer_read_start()]. This patch changes the loop exit condition to use the result of trace_find_next_entry_inc(). Effectively this switches the non-consuming kdb dumper to follow the approach of the non-consuming userspace interface [s_next()] rather than the consuming ftrace_dump(). Link: http://lkml.kernel.org/r/1415277716-19419-3-git-send-email-daniel.thompson@linaro.org Cc: Ingo Molnar <mingo@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: John Stultz <john.stultz@linaro.org> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: Jason Wessel <jason.wessel@windriver.com> Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/trace_kdb.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
index 8faa7ce58814..b0b1c44e923a 100644
--- a/kernel/trace/trace_kdb.c
+++ b/kernel/trace/trace_kdb.c
@@ -59,19 +59,19 @@ static void ftrace_dump_buf(int skip_lines, long cpu_file)
ring_buffer_read_start(iter.buffer_iter[cpu_file]);
tracing_iter_reset(&iter, cpu_file);
}
- if (!trace_empty(&iter))
- trace_find_next_entry_inc(&iter);
- while (!trace_empty(&iter)) {
+
+ while (trace_find_next_entry_inc(&iter)) {
if (!cnt)
kdb_printf("---------------------------------\n");
cnt++;
- if (trace_find_next_entry_inc(&iter) != NULL && !skip_lines)
+ if (!skip_lines) {
print_trace_line(&iter);
- if (!skip_lines)
trace_printk_seq(&iter.seq);
- else
+ } else {
skip_lines--;
+ }
+
if (KDB_FLAG(CMD_INTERRUPT))
goto out;
}