6cd247ef22
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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