ring-buffer: Always run per-cpu ring buffer resize with schedule_work_on() (021c5b34) · Commits · 戴 / test

The code for resizing the trace ring buffers has to run the per-cpu resize on the CPU itself. The code was using preempt_off() and running the code for the current CPU directly, otherwise calling schedule_work_on(). At least on RT this could result in the following: |BUG: sleeping function called from invalid context at kernel/rtmutex.c:673 |in_atomic(): 1, irqs_disabled(): 0, pid: 607, name: bash |3 locks held by bash/607: |CPU: 0 PID: 607 Comm: bash Not tainted 3.12.15-rt25+ #124 |(rt_spin_lock+0x28/0x68) |(free_hot_cold_page+0x84/0x3b8) |(free_buffer_page+0x14/0x20) |(rb_update_pages+0x280/0x338) |(ring_buffer_resize+0x32c/0x3dc) |(free_snapshot+0x18/0x38) |(tracing_set_tracer+0x27c/0x2ac) probably via |cd /sys/kernel/debug/tracing/ |echo 1 > events/enable ; sleep 2 |echo 1024 > buffer_size_kb If we just always use schedule_work_on(), there's no need for the preempt_off(). So do that. Link: http://lkml.kernel.org/p/1405537633-31518-1-git-send-email-cminyard@mvista.com Reported-by:

Stanislav Meduna <stano@meduna.org> Signed-off-by:

Corey Minyard <cminyard@mvista.com> Signed-off-by:

Steven Rostedt <rostedt@goodmis.org>

kernel/trace/ring_buffer.c

+4 −20

Original line number	Diff line number	Diff line
		@@ -1693,22 +1693,14 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
		if (!cpu_buffer->nr_pages_to_update)
		continue;

		/* The update must run on the CPU that is being updated. */
		preempt_disable();
		if (cpu == smp_processor_id() \|\| !cpu_online(cpu)) {
		/* Can't run something on an offline CPU. */
		if (!cpu_online(cpu)) {
		rb_update_pages(cpu_buffer);
		cpu_buffer->nr_pages_to_update = 0;
		} else {
		/*
		* Can not disable preemption for schedule_work_on()
		* on PREEMPT_RT.
		*/
		preempt_enable();
		schedule_work_on(cpu,
		&cpu_buffer->update_pages_work);
		preempt_disable();
		}
		preempt_enable();
		}

		/* wait for all the updates to complete */
		@@ -1746,22 +1738,14 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,

		get_online_cpus();

		preempt_disable();
		/* The update must run on the CPU that is being updated. */
		if (cpu_id == smp_processor_id() \|\| !cpu_online(cpu_id))
		/* Can't run something on an offline CPU. */
		if (!cpu_online(cpu_id))
		rb_update_pages(cpu_buffer);
		else {
		/*
		* Can not disable preemption for schedule_work_on()
		* on PREEMPT_RT.
		*/
		preempt_enable();
		schedule_work_on(cpu_id,
		&cpu_buffer->update_pages_work);
		wait_for_completion(&cpu_buffer->update_done);
		preempt_disable();
		}
		preempt_enable();

		cpu_buffer->nr_pages_to_update = 0;
		put_online_cpus();

Admin message