From f5eb5588262cab7232ed1d77cf612b327db50767 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Thu, 7 Mar 2013 09:27:42 -0500 Subject: [PATCH] ring-buffer: Do not use schedule_work_on() for current CPU The ring buffer updates when done while the ring buffer is active, needs to be completed on the CPU that is used for the ring buffer per_cpu buffer. To accomplish this, schedule_work_on() is used to schedule work on the given CPU. Now there's no reason to use schedule_work_on() if the process doing the update happens to be on the CPU that it is processing. It has already filled the requirement. Instead, just do the work and continue. This is needed for tracing_snapshot_alloc() where it may be called really early in boot, where the work queues have not been set up yet. Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 33 +++++++++++++++++++++++++++------ 1 file changed, 27 insertions(+), 6 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 65fe2a4..d1c85c5 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1679,11 +1679,22 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size, if (!cpu_buffer->nr_pages_to_update) continue; - if (cpu_online(cpu)) + /* The update must run on the CPU that is being updated. */ + preempt_disable(); + if (cpu == smp_processor_id() || !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); - else - rb_update_pages(cpu_buffer); + preempt_disable(); + } + preempt_enable(); } /* wait for all the updates to complete */ @@ -1721,12 +1732,22 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size, get_online_cpus(); - if (cpu_online(cpu_id)) { + preempt_disable(); + /* The update must run on the CPU that is being updated. */ + if (cpu_id == smp_processor_id() || !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); - } else - rb_update_pages(cpu_buffer); + preempt_disable(); + } + preempt_enable(); cpu_buffer->nr_pages_to_update = 0; put_online_cpus(); -- 2.7.4