# \[PATCH v8 12/21\] ring-buffer: Avoid reader\_lock deadlock during panic - From: Vincent Donnefort \ - Date: 2026-11-06 18:07:58 - List: linux-trace-kernel - Page: https://ratatoskr.run/linux-trace-kernel/2026/11/17880564 - Thread: https://ratatoskr.run/linux-trace-kernel/2026/11/17880557/t.md ```text Although reader_lock is taken with IRQs disabled, panic shutdown can stop CPUs with NMIs (most likely if the first attempt with maskable interrupts failed). Those NMIs may stop a CPU while it holds the reader_lock. Use trylock when panic_on_this_cpu() just like in_nmi(). Fixes: 289a5a25c5d0 ("ring-buffer: Give NMIs a chance to lock the reader_lock") Reported-by: Sashiko Closes: https://lore.kernel.org/linux-trace-kernel/20260924151509.23AEE1F000FF@smtp.kernel.org/ Signed-off-by: Vincent Donnefort --- kernel/trace/ring_buffer.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 4dab77883bd5..0dc661a95d67 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -22,6 +22,7 @@ #include /* for self test */ #include #include +#include #include #include #include @@ -6297,7 +6298,7 @@ EXPORT_SYMBOL_GPL(ring_buffer_iter_peek); static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer) { - if (likely(!in_nmi())) { + if (likely(!in_nmi() && !panic_on_this_cpu())) { raw_spin_lock(&cpu_buffer->reader_lock); return true; } -- 2.56.0.455.g6c5a503b38-goog ```