[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>
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@ -1362,11 +1362,13 @@ static inline int handler_set_err(struct v4l2_ctrl_handler *hdl, int err)
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}
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}
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/* Initialize the handler */
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/* Initialize the handler */
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int v4l2_ctrl_handler_init(struct v4l2_ctrl_handler *hdl,
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int v4l2_ctrl_handler_init_class(struct v4l2_ctrl_handler *hdl,
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unsigned nr_of_controls_hint)
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unsigned nr_of_controls_hint,
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struct lock_class_key *key, const char *name)
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{
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{
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hdl->lock = &hdl->_lock;
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hdl->lock = &hdl->_lock;
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mutex_init(hdl->lock);
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mutex_init(hdl->lock);
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lockdep_set_class_and_name(hdl->lock, key, name);
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INIT_LIST_HEAD(&hdl->ctrls);
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INIT_LIST_HEAD(&hdl->ctrls);
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INIT_LIST_HEAD(&hdl->ctrl_refs);
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INIT_LIST_HEAD(&hdl->ctrl_refs);
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hdl->nr_of_buckets = 1 + nr_of_controls_hint / 8;
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hdl->nr_of_buckets = 1 + nr_of_controls_hint / 8;
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@ -1375,7 +1377,7 @@ int v4l2_ctrl_handler_init(struct v4l2_ctrl_handler *hdl,
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hdl->error = hdl->buckets ? 0 : -ENOMEM;
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hdl->error = hdl->buckets ? 0 : -ENOMEM;
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return hdl->error;
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return hdl->error;
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}
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}
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EXPORT_SYMBOL(v4l2_ctrl_handler_init);
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EXPORT_SYMBOL(v4l2_ctrl_handler_init_class);
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/* Free all controls and control refs */
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/* Free all controls and control refs */
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void v4l2_ctrl_handler_free(struct v4l2_ctrl_handler *hdl)
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void v4l2_ctrl_handler_free(struct v4l2_ctrl_handler *hdl)
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@ -259,7 +259,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
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s32 *min, s32 *max, s32 *step, s32 *def, u32 *flags);
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s32 *min, s32 *max, s32 *step, s32 *def, u32 *flags);
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/** v4l2_ctrl_handler_init() - Initialize the control handler.
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/** v4l2_ctrl_handler_init_class() - Initialize the control handler.
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* @hdl: The control handler.
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* @hdl: The control handler.
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* @nr_of_controls_hint: A hint of how many controls this handler is
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* @nr_of_controls_hint: A hint of how many controls this handler is
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* expected to refer to. This is the total number, so including
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* expected to refer to. This is the total number, so including
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@ -268,12 +268,35 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
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* are allocated) or the control lookup becomes slower (not enough
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* are allocated) or the control lookup becomes slower (not enough
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* buckets are allocated, so there are more slow list lookups).
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* buckets are allocated, so there are more slow list lookups).
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* It will always work, though.
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* It will always work, though.
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* @key: Used by the lock validator if CONFIG_LOCKDEP is set.
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* @name: Used by the lock validator if CONFIG_LOCKDEP is set.
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*
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*
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* Returns an error if the buckets could not be allocated. This error will
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* Returns an error if the buckets could not be allocated. This error will
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* also be stored in @hdl->error.
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* also be stored in @hdl->error.
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*
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* Never use this call directly, always use the v4l2_ctrl_handler_init
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* macro that hides the @key and @name arguments.
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*/
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*/
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int v4l2_ctrl_handler_init(struct v4l2_ctrl_handler *hdl,
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int v4l2_ctrl_handler_init_class(struct v4l2_ctrl_handler *hdl,
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unsigned nr_of_controls_hint);
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unsigned nr_of_controls_hint,
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struct lock_class_key *key, const char *name);
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#ifdef CONFIG_LOCKDEP
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#define v4l2_ctrl_handler_init(hdl, nr_of_controls_hint) \
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( \
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({ \
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static struct lock_class_key _key; \
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v4l2_ctrl_handler_init_class(hdl, nr_of_controls_hint, \
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&_key, \
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KBUILD_BASENAME ":" \
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__stringify(__LINE__) ":" \
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"(" #hdl ")->_lock"); \
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}) \
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)
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#else
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#define v4l2_ctrl_handler_init(hdl, nr_of_controls_hint) \
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v4l2_ctrl_handler_init_class(hdl, nr_of_controls_hint, NULL, NULL)
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#endif
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/** v4l2_ctrl_handler_free() - Free all controls owned by the handler and free
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/** v4l2_ctrl_handler_free() - Free all controls owned by the handler and free
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* the control list.
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* the control list.
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