On Mon, 20 Jan 2025 18:56:56 -0500
Steven Rostedt <rost...@goodmis.org> wrote:
> From: Steven Rostedt <rost...@goodmis.org>
>
> Some architectures can not safely do atomic64 operations in NMI context.
> Since the ring buffer relies on atomic64 operations to do its time
> keeping, if an event is requested in NMI context, reject it for these
> architectures.
>
Looks good to me.
Reviewed-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
> Cc: sta...@vger.kernel.org
> Fixes: c84897c0ff592 ("ring-buffer: Remove 32bit timestamp logic")
> Closes:
> https://lore.kernel.org/all/86fb4f86-a0e4-45a2-a2df-3154acc4f...@gaisler.com/
> Reported-by: Ludwig Rydberg <ludwig.rydb...@gaisler.com>
> Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org>
> ---
> kernel/trace/ring_buffer.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 6d61ff78926b..b8e0ae15ca5b 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -4398,8 +4398,13 @@ rb_reserve_next_event(struct trace_buffer *buffer,
> int nr_loops = 0;
> int add_ts_default;
>
> - /* ring buffer does cmpxchg, make sure it is safe in NMI context */
> - if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) &&
> + /*
> + * ring buffer does cmpxchg as well as atomic64 operations
> + * (which some archs use locking for atomic64), make sure this
> + * is safe in NMI context
> + */
> + if ((!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) ||
> + IS_ENABLED(CONFIG_GENERIC_ATOMIC64)) &&
> (unlikely(in_nmi()))) {
> return NULL;
> }
> --
> 2.45.2
>
>
--
Masami Hiramatsu (Google) <mhira...@kernel.org>
