Commit 4f7512e7 authored Dec 13, 2023 by Steven Rostedt (Google) Committed by Greg Kroah-Hartman Jan 25, 2024

ring-buffer: Do not record in NMI if the arch does not support cmpxchg in NMI

[ Upstream commit 712292308af2265cd9b126aedfa987f10f452a33 ]

As the ring buffer recording requires cmpxchg() to work, if the
architecture does not support cmpxchg in NMI, then do not do any recording
within an NMI.

Link: https://lore.kernel.org/linux-trace-kernel/20231213175403.6fc18540@gandalf.local.home



Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent e405c22e

kernel/trace/ring_buffer.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -2976,6 +2976,12 @@ rb_reserve_next_event(struct ring_buffer *buffer,
		int nr_loops = 0;
		u64 diff;

		/* ring buffer does cmpxchg, make sure it is safe in NMI context */
		if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) &&
		(unlikely(in_nmi()))) {
		return NULL;
		}

		rb_start_commit(cpu_buffer);

		#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP