From 6cd247ef22e493e1884e576c066661538b031981 Mon Sep 17 00:00:00 2001 From: Andy Walls Date: Sat, 9 Mar 2013 05:55:11 -0300 Subject: [media] v4l2-ctrls: eliminate lockdep false alarms for struct v4l2_ctrl_handler.lock When calling v4l2_ctrl_add_handler(), lockdep would detect a potential recursive locking problem on a situation that is by design intended and not a recursive lock. This happened because all struct v4l2_ctrl_handler.lock mutexes were created as members of the same lock class in v4l2_ctrl_handler_init(), and v4l2_ctrl_add_handler() takes the hdl->lock on two different v4l2_ctrl_handler instances. This change breaks the large lockdep lock class for struct v4l2_ctrl_handler.lock and breaks it into v4l2_ctrl_handler instantiation specific lock classes with meaningful class names. This will validly eliminate lockdep alarms for v4l2_ctrl_handler locking validation, as long as the relationships between drivers adding v4l2 controls to their own handler from other v4l2 drivers' control handlers remains straightforward. struct v4l2_ctrl_handler.lock lock classes are created with names such that the output of cat /proc/lockdep indicates where in the v4l2 driver code v4l2_ctrl_handle_init() is being called on instantiations: ffffffffa045f490 FD: 10 BD: 8 +.+...: cx2341x:1534:(hdl)->lock ffffffffa0497d20 FD: 12 BD: 2 +.+.+.: saa7115:1581:(hdl)->lock ffffffffa04ac660 FD: 14 BD: 2 +.+.+.: msp3400_driver:756:(hdl)->lock ffffffffa0484b90 FD: 12 BD: 1 +.+.+.: ivtv_gpio:366:(&itv->hdl_gpio)->lock ffffffffa04eb530 FD: 11 BD: 2 +.+.+.: cx25840_core:1982:(&state->hdl)->lock ffffffffa04fbc80 FD: 11 BD: 3 +.+.+.: wm8775:246:(&state->hdl)->lock Some lock chains, that were previously causing the recursion alarms, are now visible in the output of cat /proc/lockdep_chains: irq_context: 0 [ffffffffa0497d20] saa7115:1581:(hdl)->lock [ffffffffa045f490] cx2341x:1534:(hdl)->lock irq_context: 0 [ffffffffa04ac660] msp3400_driver:756:(hdl)->lock [ffffffffa045f490] cx2341x:1534:(hdl)->lock irq_context: 0 [ffffffffa0484b90] ivtv_gpio:366:(&itv->hdl_gpio)->lock [ffffffffa045f490] cx2341x:1534:(hdl)->lock irq_context: 0 [ffffffffa04eb530] cx25840_core:1982:(&state->hdl)->lock [ffffffffa045f490] cx2341x:1534:(hdl)->lock irq_context: 0 [ffffffffa04fbc80] wm8775:246:(&state->hdl)->lock [ffffffffa045f490] cx2341x:1534:(hdl)->lock Signed-off-by: Andy Walls [hans.verkuil@cisco.com: keep mutex_init in v4l2_ctrl_handler_init_class] Signed-off-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab --- drivers/media/v4l2-core/v4l2-ctrls.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'drivers') diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c index 6b28b5800500..b36d1ec13ee6 100644 --- a/drivers/media/v4l2-core/v4l2-ctrls.c +++ b/drivers/media/v4l2-core/v4l2-ctrls.c @@ -1362,11 +1362,13 @@ static inline int handler_set_err(struct v4l2_ctrl_handler *hdl, int err) } /* Initialize the handler */ -int v4l2_ctrl_handler_init(struct v4l2_ctrl_handler *hdl, - unsigned nr_of_controls_hint) +int v4l2_ctrl_handler_init_class(struct v4l2_ctrl_handler *hdl, + unsigned nr_of_controls_hint, + struct lock_class_key *key, const char *name) { hdl->lock = &hdl->_lock; mutex_init(hdl->lock); + lockdep_set_class_and_name(hdl->lock, key, name); INIT_LIST_HEAD(&hdl->ctrls); INIT_LIST_HEAD(&hdl->ctrl_refs); hdl->nr_of_buckets = 1 + nr_of_controls_hint / 8; @@ -1375,7 +1377,7 @@ int v4l2_ctrl_handler_init(struct v4l2_ctrl_handler *hdl, hdl->error = hdl->buckets ? 0 : -ENOMEM; return hdl->error; } -EXPORT_SYMBOL(v4l2_ctrl_handler_init); +EXPORT_SYMBOL(v4l2_ctrl_handler_init_class); /* Free all controls and control refs */ void v4l2_ctrl_handler_free(struct v4l2_ctrl_handler *hdl) -- cgit v1.2.3