Ping, I haven't heard anything on this. -corey
On 07/16/2014 02:07 PM, [email protected] wrote: > From: Corey Minyard <[email protected]> > > 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. > > Reported-by: Stanislav Meduna <[email protected]> > Signed-off-by: Corey Minyard <[email protected]> > --- > kernel/trace/ring_buffer.c | 24 ++++-------------------- > 1 file changed, 4 insertions(+), 20 deletions(-) > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index 7c56c3d..35825a8 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -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(); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
