From: Sven Schnelle svens@linux.ibm.com
[ Upstream commit 7acf3a127bb7c65ff39099afd78960e77b2ca5de ]
Booting the kernel with 'trace_buf_size=1' give a warning at boot during the ftrace selftests:
[ 0.892809] Running postponed tracer tests: [ 0.892893] Testing tracer function: [ 0.901899] Callback from call_rcu_tasks_trace() invoked. [ 0.983829] Callback from call_rcu_tasks_rude() invoked. [ 1.072003] .. bad ring buffer .. corrupted trace buffer .. [ 1.091944] Callback from call_rcu_tasks() invoked. [ 1.097695] PASSED [ 1.097701] Testing dynamic ftrace: .. filter failed count=0 ..FAILED! [ 1.353474] ------------[ cut here ]------------ [ 1.353478] WARNING: CPU: 0 PID: 1 at kernel/trace/trace.c:1951 run_tracer_selftest+0x13c/0x1b0
Therefore enforce a minimum of 4096 bytes to make the selftest pass.
Link: https://lkml.kernel.org/r/20220214134456.1751749-1-svens@linux.ibm.com
Signed-off-by: Sven Schnelle svens@linux.ibm.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/trace/trace.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 86fb77c2ace5..01002656f1ae 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1496,10 +1496,12 @@ static int __init set_buf_size(char *str) if (!str) return 0; buf_size = memparse(str, &str); - /* nr_entries can not be zero */ - if (buf_size == 0) - return 0; - trace_buf_size = buf_size; + /* + * nr_entries can not be zero and the startup + * tests require some buffer space. Therefore + * ensure we have at least 4096 bytes of buffer. + */ + trace_buf_size = max(4096UL, buf_size); return 1; } __setup("trace_buf_size=", set_buf_size);