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author | Andy Walls <awalls@md.metrocast.net> | 2013-03-09 08:55:11 (GMT) |
---|---|---|
committer | Mauro Carvalho Chehab <mchehab@redhat.com> | 2013-03-24 14:47:09 (GMT) |
commit | 6cd247ef22e493e1884e576c066661538b031981 (patch) | |
tree | c8293aafc52bc1db11ec7b52c1df31b456cd2816 /drivers/media/v4l2-core/v4l2-ctrls.c | |
parent | 842059aa4796d7c59bc3801d48896ba06b1a1287 (diff) | |
download | linux-fsl-qoriq-6cd247ef22e493e1884e576c066661538b031981.tar.xz |
[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 <awalls@md.metrocast.net>
[hans.verkuil@cisco.com: keep mutex_init in v4l2_ctrl_handler_init_class]
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'drivers/media/v4l2-core/v4l2-ctrls.c')
-rw-r--r-- | drivers/media/v4l2-core/v4l2-ctrls.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c index 6b28b58..b36d1ec 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) |