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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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tracing: Disable trace_printk buffer on warning too

When /proc/sys/kernel/traceoff_on_warning is set to 1, the top level
tracing buffer is disabled when a warning happens. This is very useful
when debugging and want the tracing buffer to stop taking new data when a
warning triggers keeping the events that lead up to the warning from being
overwritten.

Now that there is also a persistent ring buffer and an option to have
trace_printk go to that buffer, the same holds true for that buffer. A
warning could happen just before a crash but still write enough events to
lose the events that lead up to the first warning that was the reason for
the crash.

When /proc/sys/kernel/traceoff_on_warning is set to 1 and a warning is
triggered, not only disable the top level tracing buffer, but also disable
the buffer that trace_printk()s are written to.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Link: https://patch.msgid.link/20260121093858.5c5d7e7b@gandalf.local.home
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Steven Rostedt 6bdf0730 a9e0c589

+9
+9
kernel/trace/trace.c
··· 1666 1666 void disable_trace_on_warning(void) 1667 1667 { 1668 1668 if (__disable_trace_on_warning) { 1669 + struct trace_array *tr = READ_ONCE(printk_trace); 1670 + 1669 1671 trace_array_printk_buf(global_trace.array_buffer.buffer, _THIS_IP_, 1670 1672 "Disabling tracing due to warning\n"); 1671 1673 tracing_off(); 1674 + 1675 + /* Disable trace_printk() buffer too */ 1676 + if (tr != &global_trace) { 1677 + trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_, 1678 + "Disabling tracing due to warning\n"); 1679 + tracer_tracing_off(tr); 1680 + } 1672 1681 } 1673 1682 } 1674 1683