From: Steven Rostedt Impact: fix to prevent hard lockup on self tests If one of the tracers are broken and is constantly filling the ring buffer while the test of the ring buffer is running, it will hang the box. The reason is that the test is a consumer that will not stop till the ring buffer is empty. But if the tracer is broken and is constantly producing input to the buffer, this test will never end. The result is a lockup of the box. This happened when KALLSYMS was not defined and the dynamic ftrace test constantly filled the ring buffer, because the filter failed and all functions were being traced. Something was being called that constantly filled the buffer. Signed-off-by: Steven Rostedt --- kernel/trace/trace_selftest.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-) diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c index 88c8eb7..a7e0ef6 100644 --- a/kernel/trace/trace_selftest.c +++ b/kernel/trace/trace_selftest.c @@ -57,11 +57,20 @@ static int trace_test_buffer(struct trace_array *tr, unsigned long *count) cnt = ring_buffer_entries(tr->buffer); + /* + * The trace_test_buffer_cpu runs a while loop to consume all data. + * If the calling tracer is broken, and is constantly filling + * the buffer, this will run forever, and hard lock the box. + * We disable the ring buffer while we do this test to prevent + * a hard lock up. + */ + tracing_off(); for_each_possible_cpu(cpu) { ret = trace_test_buffer_cpu(tr, cpu); if (ret) break; } + tracing_on(); __raw_spin_unlock(&ftrace_max_lock); local_irq_restore(flags); -- 1.5.6.5 -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/