From 1f8a6a10fb9437eac3f516ea4324a19087872f30 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 8 Jun 2009 18:18:39 +0200 Subject: 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: [] ring_buffer_reset_cpu+0x37/0x70 > > but task is already holding lock: > (&cpu_buffer->reader_lock){......}, at: [] 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: [] 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 Signed-off-by: Peter Zijlstra LKML-Reference: <1244477919.13761.9042.camel@twins> [ store key in ring buffer descriptor ] Signed-off-by: Steven Rostedt --- include/linux/ring_buffer.h | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) (limited to 'include/linux/ring_buffer.h') diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index f1345828c7c5..8670f1575fe1 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); -- cgit v1.3-14-g43fede From 1744a21d57d9c60136461adb6afa85e51b3e94d9 Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Sat, 28 Feb 2009 08:29:44 +0100 Subject: trace: annotate bitfields in struct ring_buffer_event This gets rid of a heap of false-positive warnings from the tracer code due to the use of bitfields. [rebased for mainline inclusion] Signed-off-by: Vegard Nossum --- include/linux/ring_buffer.h | 4 ++++ kernel/trace/ring_buffer.c | 3 +++ 2 files changed, 7 insertions(+) (limited to 'include/linux/ring_buffer.h') diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index 8670f1575fe1..29f8599e6bea 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -1,6 +1,7 @@ #ifndef _LINUX_RING_BUFFER_H #define _LINUX_RING_BUFFER_H +#include #include #include @@ -11,7 +12,10 @@ struct ring_buffer_iter; * Don't refer to this struct directly, use functions below. */ struct ring_buffer_event { + kmemcheck_bitfield_begin(bitfield); u32 type_len:5, time_delta:27; + kmemcheck_bitfield_end(bitfield); + u32 array[]; }; diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 2e642b2b7253..dc4dc70171ce 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -10,6 +10,7 @@ #include #include #include +#include #include #include #include @@ -1270,6 +1271,7 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer, if (tail < BUF_PAGE_SIZE) { /* Mark the rest of the page with padding */ event = __rb_page_index(tail_page, tail); + kmemcheck_annotate_bitfield(event, bitfield); rb_event_set_padding(event); } @@ -1327,6 +1329,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, return NULL; event = __rb_page_index(tail_page, tail); + kmemcheck_annotate_bitfield(event, bitfield); rb_update_event(event, type, length); /* The passed in type is zero for DATA */ -- cgit v1.3-14-g43fede