The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x b538bf7d0ec11ca49f536dfda742a5f6db90a798 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023120908-crisply-trash-d37e@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

b538bf7d0ec1 ("tracing: Disable snapshot buffer when stopping instance tracers") 13292494379f ("tracing: Make struct ring_buffer less ambiguous") 1c5eb4481e01 ("tracing: Rename trace_buffer to array_buffer") 2d6425af6116 ("tracing: Declare newly exported APIs in include/linux/trace.h")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b538bf7d0ec11ca49f536dfda742a5f6db90a798 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Google)" rostedt@goodmis.org Date: Tue, 5 Dec 2023 16:52:11 -0500 Subject: [PATCH] tracing: Disable snapshot buffer when stopping instance tracers

It use to be that only the top level instance had a snapshot buffer (for latency tracers like wakeup and irqsoff). When stopping a tracer in an instance would not disable the snapshot buffer. This could have some unintended consequences if the irqsoff tracer is enabled.

Consolidate the tracing_start/stop() with tracing_start/stop_tr() so that all instances behave the same. The tracing_start/stop() functions will just call their respective tracing_start/stop_tr() with the global_array passed in.

Link: https://lkml.kernel.org/r/20231205220011.041220035@goodmis.org

Cc: stable@vger.kernel.org Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mark Rutland mark.rutland@arm.com Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Andrew Morton akpm@linux-foundation.org Fixes: 6d9b3fa5e7f6 ("tracing: Move tracing_max_latency into trace_array") Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index e978868b1a22..2492c6c76850 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2360,49 +2360,6 @@ int is_tracing_stopped(void) return global_trace.stop_count; }

-/** - * tracing_start - quick start of the tracer - * - * If tracing is enabled but was stopped by tracing_stop, - * this will start the tracer back up. - */ -void tracing_start(void) -{ - struct trace_buffer *buffer; - unsigned long flags; - - if (tracing_disabled) - return; - - raw_spin_lock_irqsave(&global_trace.start_lock, flags); - if (--global_trace.stop_count) { - if (global_trace.stop_count < 0) { - /* Someone screwed up their debugging */ - WARN_ON_ONCE(1); - global_trace.stop_count = 0; - } - goto out; - } - - /* Prevent the buffers from switching */ - arch_spin_lock(&global_trace.max_lock); - - buffer = global_trace.array_buffer.buffer; - if (buffer) - ring_buffer_record_enable(buffer); - -#ifdef CONFIG_TRACER_MAX_TRACE - buffer = global_trace.max_buffer.buffer; - if (buffer) - ring_buffer_record_enable(buffer); -#endif - - arch_spin_unlock(&global_trace.max_lock); - - out: - raw_spin_unlock_irqrestore(&global_trace.start_lock, flags); -} - static void tracing_start_tr(struct trace_array *tr) { struct trace_buffer *buffer; @@ -2411,25 +2368,70 @@ static void tracing_start_tr(struct trace_array *tr) if (tracing_disabled) return;

- /* If global, we need to also start the max tracer */ - if (tr->flags & TRACE_ARRAY_FL_GLOBAL) - return tracing_start(); - raw_spin_lock_irqsave(&tr->start_lock, flags); - if (--tr->stop_count) { - if (tr->stop_count < 0) { + if (WARN_ON_ONCE(tr->stop_count < 0)) { /* Someone screwed up their debugging */ - WARN_ON_ONCE(1); tr->stop_count = 0; } goto out; }

+ /* Prevent the buffers from switching */ + arch_spin_lock(&tr->max_lock); + buffer = tr->array_buffer.buffer; if (buffer) ring_buffer_record_enable(buffer);

+#ifdef CONFIG_TRACER_MAX_TRACE + buffer = tr->max_buffer.buffer; + if (buffer) + ring_buffer_record_enable(buffer); +#endif + + arch_spin_unlock(&tr->max_lock); + + out: + raw_spin_unlock_irqrestore(&tr->start_lock, flags); +} + +/** + * tracing_start - quick start of the tracer + * + * If tracing is enabled but was stopped by tracing_stop, + * this will start the tracer back up. + */ +void tracing_start(void) + +{ + return tracing_start_tr(&global_trace); +} + +static void tracing_stop_tr(struct trace_array *tr) +{ + struct trace_buffer *buffer; + unsigned long flags; + + raw_spin_lock_irqsave(&tr->start_lock, flags); + if (tr->stop_count++) + goto out; + + /* Prevent the buffers from switching */ + arch_spin_lock(&tr->max_lock); + + buffer = tr->array_buffer.buffer; + if (buffer) + ring_buffer_record_disable(buffer); + +#ifdef CONFIG_TRACER_MAX_TRACE + buffer = tr->max_buffer.buffer; + if (buffer) + ring_buffer_record_disable(buffer); +#endif + + arch_spin_unlock(&tr->max_lock); + out: raw_spin_unlock_irqrestore(&tr->start_lock, flags); } @@ -2442,51 +2444,7 @@ static void tracing_start_tr(struct trace_array *tr) */ void tracing_stop(void) { - struct trace_buffer *buffer; - unsigned long flags; - - raw_spin_lock_irqsave(&global_trace.start_lock, flags); - if (global_trace.stop_count++) - goto out; - - /* Prevent the buffers from switching */ - arch_spin_lock(&global_trace.max_lock); - - buffer = global_trace.array_buffer.buffer; - if (buffer) - ring_buffer_record_disable(buffer); - -#ifdef CONFIG_TRACER_MAX_TRACE - buffer = global_trace.max_buffer.buffer; - if (buffer) - ring_buffer_record_disable(buffer); -#endif - - arch_spin_unlock(&global_trace.max_lock); - - out: - raw_spin_unlock_irqrestore(&global_trace.start_lock, flags); -} - -static void tracing_stop_tr(struct trace_array *tr) -{ - struct trace_buffer *buffer; - unsigned long flags; - - /* If global, we need to also stop the max tracer */ - if (tr->flags & TRACE_ARRAY_FL_GLOBAL) - return tracing_stop(); - - raw_spin_lock_irqsave(&tr->start_lock, flags); - if (tr->stop_count++) - goto out; - - buffer = tr->array_buffer.buffer; - if (buffer) - ring_buffer_record_disable(buffer); - - out: - raw_spin_unlock_irqrestore(&tr->start_lock, flags); + return tracing_stop_tr(&global_trace); }

static int trace_save_cmdline(struct task_struct *tsk)