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authorAndy Walls <awalls@md.metrocast.net>2013-03-09 12:55:11 +0400
committerMauro Carvalho Chehab <mchehab@redhat.com>2013-03-24 18:47:09 +0400
commit6cd247ef22e493e1884e576c066661538b031981 (patch)
treec8293aafc52bc1db11ec7b52c1df31b456cd2816 /include/media/v4l2-ctrls.h
parent842059aa4796d7c59bc3801d48896ba06b1a1287 (diff)
downloadlinux-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 'include/media/v4l2-ctrls.h')
-rw-r--r--include/media/v4l2-ctrls.h29
1 files changed, 26 insertions, 3 deletions
diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
index f00d42bc01a6..7343a27fe819 100644
--- a/include/media/v4l2-ctrls.h
+++ b/include/media/v4l2-ctrls.h
@@ -259,7 +259,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
s32 *min, s32 *max, s32 *step, s32 *def, u32 *flags);
-/** v4l2_ctrl_handler_init() - Initialize the control handler.
+/** v4l2_ctrl_handler_init_class() - Initialize the control handler.
* @hdl: The control handler.
* @nr_of_controls_hint: A hint of how many controls this handler is
* expected to refer to. This is the total number, so including
@@ -268,12 +268,35 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
* are allocated) or the control lookup becomes slower (not enough
* buckets are allocated, so there are more slow list lookups).
* It will always work, though.
+ * @key: Used by the lock validator if CONFIG_LOCKDEP is set.
+ * @name: Used by the lock validator if CONFIG_LOCKDEP is set.
*
* Returns an error if the buckets could not be allocated. This error will
* also be stored in @hdl->error.
+ *
+ * Never use this call directly, always use the v4l2_ctrl_handler_init
+ * macro that hides the @key and @name arguments.
*/
-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);
+
+#ifdef CONFIG_LOCKDEP
+#define v4l2_ctrl_handler_init(hdl, nr_of_controls_hint) \
+( \
+ ({ \
+ static struct lock_class_key _key; \
+ v4l2_ctrl_handler_init_class(hdl, nr_of_controls_hint, \
+ &_key, \
+ KBUILD_BASENAME ":" \
+ __stringify(__LINE__) ":" \
+ "(" #hdl ")->_lock"); \
+ }) \
+)
+#else
+#define v4l2_ctrl_handler_init(hdl, nr_of_controls_hint) \
+ v4l2_ctrl_handler_init_class(hdl, nr_of_controls_hint, NULL, NULL)
+#endif
/** v4l2_ctrl_handler_free() - Free all controls owned by the handler and free
* the control list.