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ring-buffer: Always run per-cpu ring buffer resize with schedule_work_on()
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>
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@ -1693,22 +1693,14 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
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if (!cpu_buffer->nr_pages_to_update)
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continue;
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/* The update must run on the CPU that is being updated. */
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preempt_disable();
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if (cpu == smp_processor_id() || !cpu_online(cpu)) {
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/* Can't run something on an offline CPU. */
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if (!cpu_online(cpu)) {
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rb_update_pages(cpu_buffer);
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cpu_buffer->nr_pages_to_update = 0;
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} else {
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/*
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* Can not disable preemption for schedule_work_on()
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* on PREEMPT_RT.
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*/
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preempt_enable();
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schedule_work_on(cpu,
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&cpu_buffer->update_pages_work);
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preempt_disable();
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}
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preempt_enable();
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}
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/* wait for all the updates to complete */
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@ -1746,22 +1738,14 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
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get_online_cpus();
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preempt_disable();
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/* The update must run on the CPU that is being updated. */
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if (cpu_id == smp_processor_id() || !cpu_online(cpu_id))
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/* Can't run something on an offline CPU. */
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if (!cpu_online(cpu_id))
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rb_update_pages(cpu_buffer);
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else {
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/*
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* Can not disable preemption for schedule_work_on()
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* on PREEMPT_RT.
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*/
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preempt_enable();
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schedule_work_on(cpu_id,
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&cpu_buffer->update_pages_work);
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wait_for_completion(&cpu_buffer->update_done);
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preempt_disable();
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}
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preempt_enable();
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cpu_buffer->nr_pages_to_update = 0;
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put_online_cpus();
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