* Stanislav Meduna | 2014-04-18 22:36:40 [+0200]:
>Hi,
Hi,
>BUG: sleeping function called from invalid context at /home/stano/Kernels/linux-3.12-rt/kernel/rtmutex.c:673
>in_atomic(): 1, irqs_disabled(): 0, pid: 607, name: bash
>3 locks held by bash/607:
> #0: (sb_writers#8){......}, at: [<c00de6f4>] vfs_write+0x1cc/0x1d0
> #1: (trace_types_lock){......}, at: [<c0087764>] tracing_set_tracer+0x1c/0x2ac
> #2: (&buffer->mutex#2){......}, at: [<c0080220>] ring_buffer_resize+0xac/0x3dc
>Preemption disabled at:[< (null)>] (null)
>
>CPU: 0 PID: 607 Comm: bash Not tainted 3.12.15-rt25+ #124
>[<c02f7010>] (rt_spin_lock+0x28/0x68) from [<c00aa468>] (free_hot_cold_page+0x84/0x3b8)
>[<c00aa468>] (free_hot_cold_page+0x84/0x3b8) from [<c007cb2c>] (free_buffer_page+0x14/0x20)
>[<c007cb2c>] (free_buffer_page+0x14/0x20) from [<c00800bc>] (rb_update_pages+0x280/0x338)
>[<c00800bc>] (rb_update_pages+0x280/0x338) from [<c00804a0>] (ring_buffer_resize+0x32c/0x3dc)
>[<c00804a0>] (ring_buffer_resize+0x32c/0x3dc) from [<c0087530>] (free_snapshot+0x18/0x38)
>[<c0087530>] (free_snapshot+0x18/0x38) from [<c00879c4>] (tracing_set_tracer+0x27c/0x2ac)
>[<c00879c4>] (tracing_set_tracer+0x27c/0x2ac) from [<c0087a4c>] (tracing_set_trace_write+0x58/0x114)
Can be triggered by:
| cd /sys/kernel/debug/tracing/
| echo 1 > events/enable
| sleep 2 # fill the buffer
| echo 1024 > buffer_size_kb # shrink the buffer
the shrinking of the buffer does this.
Steven, are you comfortable with this change:
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index fc4da2d..112d4a5 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1682,28 +1682,22 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
* We can't schedule on offline CPUs, but it's not necessary
* since we can change their buffer sizes without any race.
*/
+ migrate_disable();
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
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)) {
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();
}
+ migrate_enable();
/* wait for all the updates to complete */
for_each_buffer_cpu(buffer, cpu) {
@@ -1740,22 +1734,16 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
get_online_cpus();
- preempt_disable();
+ migrate_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);
- preempt_disable();
}
- preempt_enable();
+ migrate_enable();
cpu_buffer->nr_pages_to_update = 0;
put_online_cpus();
--
2.0.0.rc0
>Thanks
Sebastian
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