diff options
| -rw-r--r-- | kernel/trace/ring_buffer.c | 59 |
1 files changed, 51 insertions, 8 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 969f7cbe8e93..589b3eedfa67 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -2466,6 +2466,21 @@ rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts) } EXPORT_SYMBOL_GPL(ring_buffer_iter_peek); +static inline int rb_ok_to_lock(void) +{ + /* + * If an NMI die dumps out the content of the ring buffer + * do not grab locks. We also permanently disable the ring + * buffer too. A one time deal is all you get from reading + * the ring buffer from an NMI. + */ + if (likely(!in_nmi() && !oops_in_progress)) + return 1; + + tracing_off_permanent(); + return 0; +} + /** * ring_buffer_peek - peek at the next event to be read * @buffer: The ring buffer to read @@ -2481,14 +2496,20 @@ ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts) struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; struct ring_buffer_event *event; unsigned long flags; + int dolock; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return NULL; + dolock = rb_ok_to_lock(); again: - spin_lock_irqsave(&cpu_buffer->reader_lock, flags); + local_irq_save(flags); + if (dolock) + spin_lock(&cpu_buffer->reader_lock); event = rb_buffer_peek(buffer, cpu, ts); - spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); + if (dolock) + spin_unlock(&cpu_buffer->reader_lock); + local_irq_restore(flags); if (event && event->type_len == RINGBUF_TYPE_PADDING) { cpu_relax(); @@ -2540,6 +2561,9 @@ ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts) struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event = NULL; unsigned long flags; + int dolock; + + dolock = rb_ok_to_lock(); again: /* might be called in atomic */ @@ -2549,7 +2573,9 @@ ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts) goto out; cpu_buffer = buffer->buffers[cpu]; - spin_lock_irqsave(&cpu_buffer->reader_lock, flags); + local_irq_save(flags); + if (dolock) + spin_lock(&cpu_buffer->reader_lock); event = rb_buffer_peek(buffer, cpu, ts); if (!event) @@ -2558,7 +2584,9 @@ ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts) rb_advance_reader(cpu_buffer); out_unlock: - spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); + if (dolock) + spin_unlock(&cpu_buffer->reader_lock); + local_irq_restore(flags); out: preempt_enable(); @@ -2757,15 +2785,23 @@ int ring_buffer_empty(struct ring_buffer *buffer) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags; + int dolock; int cpu; int ret; + dolock = rb_ok_to_lock(); + /* yes this is racy, but if you don't like the race, lock the buffer */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; - spin_lock_irqsave(&cpu_buffer->reader_lock, flags); + local_irq_save(flags); + if (dolock) + spin_lock(&cpu_buffer->reader_lock); ret = rb_per_cpu_empty(cpu_buffer); - spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); + if (dolock) + spin_unlock(&cpu_buffer->reader_lock); + local_irq_restore(flags); + if (!ret) return 0; } @@ -2783,15 +2819,22 @@ int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags; + int dolock; int ret; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 1; + dolock = rb_ok_to_lock(); + cpu_buffer = buffer->buffers[cpu]; - spin_lock_irqsave(&cpu_buffer->reader_lock, flags); + local_irq_save(flags); + if (dolock) + spin_lock(&cpu_buffer->reader_lock); ret = rb_per_cpu_empty(cpu_buffer); - spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); + if (dolock) + spin_unlock(&cpu_buffer->reader_lock); + local_irq_restore(flags); return ret; } |