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authorPeter Zijlstra <peterz@infradead.org>2009-06-08 18:18:39 +0200
committerSteven Rostedt <rostedt@goodmis.org>2009-06-08 18:50:20 -0400
commit1f8a6a10fb9437eac3f516ea4324a19087872f30 (patch)
tree944f73519ef205c3baccd130d93ed70f7e7bc790
parent918143e8b7d6153d7a83a3f854323407939f4a7e (diff)
ring-buffer: pass in lockdep class key for reader_lock
On Sun, 7 Jun 2009, Ingo Molnar wrote: > Testing tracer sched_switch: <6>Starting ring buffer hammer > PASSED > Testing tracer sysprof: PASSED > Testing tracer function: PASSED > Testing tracer irqsoff: > ============================================= > PASSED > Testing tracer preemptoff: PASSED > Testing tracer preemptirqsoff: [ INFO: possible recursive locking detected ] > PASSED > Testing tracer branch: 2.6.30-rc8-tip-01972-ge5b9078-dirty #5760 > --------------------------------------------- > rb_consumer/431 is trying to acquire lock: > (&cpu_buffer->reader_lock){......}, at: [<c109eef7>] ring_buffer_reset_cpu+0x37/0x70 > > but task is already holding lock: > (&cpu_buffer->reader_lock){......}, at: [<c10a019e>] ring_buffer_consume+0x7e/0xc0 > > other info that might help us debug this: > 1 lock held by rb_consumer/431: > #0: (&cpu_buffer->reader_lock){......}, at: [<c10a019e>] ring_buffer_consume+0x7e/0xc0 The ring buffer is a generic structure, and can be used outside of ftrace. If ftrace traces within the use of the ring buffer, it can produce false positives with lockdep. This patch passes in a static lock key into the allocation of the ring buffer, so that different ring buffers will have their own lock class. Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1244477919.13761.9042.camel@twins> [ store key in ring buffer descriptor ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
-rw-r--r--include/linux/ring_buffer.h14
-rw-r--r--kernel/trace/ring_buffer.c9
2 files changed, 20 insertions, 3 deletions
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index f1345828c7c..8670f1575fe 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -105,7 +105,19 @@ void ring_buffer_discard_commit(struct ring_buffer *buffer,
* size is in bytes for each per CPU buffer.
*/
struct ring_buffer *
-ring_buffer_alloc(unsigned long size, unsigned flags);
+__ring_buffer_alloc(unsigned long size, unsigned flags, struct lock_class_key *key);
+
+/*
+ * Because the ring buffer is generic, if other users of the ring buffer get
+ * traced by ftrace, it can produce lockdep warnings. We need to keep each
+ * ring buffer's lock class separate.
+ */
+#define ring_buffer_alloc(size, flags) \
+({ \
+ static struct lock_class_key __key; \
+ __ring_buffer_alloc((size), (flags), &__key); \
+})
+
void ring_buffer_free(struct ring_buffer *buffer);
int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size);
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 7102d7a2fad..22878b0d370 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -426,6 +426,8 @@ struct ring_buffer {
atomic_t record_disabled;
cpumask_var_t cpumask;
+ struct lock_class_key *reader_lock_key;
+
struct mutex mutex;
struct ring_buffer_per_cpu **buffers;
@@ -565,6 +567,7 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
cpu_buffer->cpu = cpu;
cpu_buffer->buffer = buffer;
spin_lock_init(&cpu_buffer->reader_lock);
+ lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
cpu_buffer->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
INIT_LIST_HEAD(&cpu_buffer->pages);
@@ -635,7 +638,8 @@ static int rb_cpu_notify(struct notifier_block *self,
* when the buffer wraps. If this flag is not set, the buffer will
* drop data when the tail hits the head.
*/
-struct ring_buffer *ring_buffer_alloc(unsigned long size, unsigned flags)
+struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
+ struct lock_class_key *key)
{
struct ring_buffer *buffer;
int bsize;
@@ -658,6 +662,7 @@ struct ring_buffer *ring_buffer_alloc(unsigned long size, unsigned flags)
buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
buffer->flags = flags;
buffer->clock = trace_clock_local;
+ buffer->reader_lock_key = key;
/* need at least two pages */
if (buffer->pages == 1)
@@ -715,7 +720,7 @@ struct ring_buffer *ring_buffer_alloc(unsigned long size, unsigned flags)
kfree(buffer);
return NULL;
}
-EXPORT_SYMBOL_GPL(ring_buffer_alloc);
+EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
/**
* ring_buffer_free - free a ring buffer.