From b410dae43cd0dc9aa07f9ada54a7b78d0fd75566 Mon Sep 17 00:00:00 2001 From: Antti Palosaari Date: Thu, 18 Dec 2014 07:22:46 -0300 Subject: [PATCH] [media] rtl2832: implement own lock for regmap Introduce own lock to silence lockdep warning. lockdep validator makes wrong decision when two similar (&map->mutex) locks were taken recursively, even those are different mutexes in a two different drivers. After that patch, functionality remains same, but mutex names are different. That is a temporary hack, proper solution is make regmap aware of locked nested locking rules. ============================================= [ INFO: possible recursive locking detected ] 3.18.0-rc4+ #4 Tainted: G O --------------------------------------------- kdvb-ad-0-fe-0/2814 is trying to acquire lock: (&map->mutex){+.+.+.}, at: [] regmap_lock_mutex+0x2f/0x40 but task is already holding lock: (&map->mutex){+.+.+.}, at: [] regmap_lock_mutex+0x2f/0x40 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&map->mutex); lock(&map->mutex); *** DEADLOCK *** May be due to missing lock nesting notation 1 lock held by kdvb-ad-0-fe-0/2814: #0: (&map->mutex){+.+.+.}, at: [] regmap_lock_mutex+0x2f/0x40 stack backtrace: CPU: 3 PID: 2814 Comm: kdvb-ad-0-fe-0 Tainted: G O 3.18.0-rc4+ #4 Hardware name: System manufacturer System Product Name/M5A78L-M/USB3, BIOS 2001 09/11/2014 0000000000000000 00000000410c8772 ffff880293af3868 ffffffff817a6f82 0000000000000000 ffff8800b3462be0 ffff880293af3968 ffffffff810e7f94 ffff880293af3888 00000000410c8772 ffffffff82dfee60 ffffffff81ab8f89 Call Trace: [] dump_stack+0x4e/0x68 [] __lock_acquire+0x1ea4/0x1f50 [] ? trace_hardirqs_off+0xd/0x10 [] ? _raw_spin_lock_irqsave+0x83/0xa0 [] ? up+0x16/0x50 [] ? trace_hardirqs_off+0xd/0x10 [] ? _raw_spin_unlock_irqrestore+0x5f/0x70 [] lock_acquire+0xc9/0x170 [] ? regmap_lock_mutex+0x2f/0x40 [] mutex_lock_nested+0x7e/0x430 [] ? regmap_lock_mutex+0x2f/0x40 [] ? regmap_lock_mutex+0x2f/0x40 [] ? printk+0x70/0x86 [] ? mod_timer+0x168/0x240 [] regmap_lock_mutex+0x2f/0x40 [] regmap_update_bits+0x29/0x60 [] rtl2832_select+0x38/0x70 [rtl2832] [] i2c_mux_master_xfer+0x3d/0x90 [i2c_mux] [] __i2c_transfer+0x73/0x2e0 [] i2c_transfer+0x5a/0xc0 [] i2c_master_send+0x4e/0x70 [] regmap_i2c_write+0x1a/0x50 [regmap_i2c] [] ? mutex_lock_nested+0x283/0x430 [] _regmap_raw_write+0x862/0x880 [] ? regmap_lock_mutex+0x2f/0x40 [] _regmap_bus_raw_write+0x74/0xa0 [] _regmap_write+0x92/0x140 [] regmap_write+0x4b/0x70 [] ? dvb_frontend_release+0x110/0x110 [dvb_core] [] e4000_init+0x34/0x210 [e4000] [] dvb_frontend_init+0x59/0xc0 [dvb_core] [] ? finish_task_switch+0x80/0x180 [] ? finish_task_switch+0x42/0x180 [] dvb_frontend_thread+0x86/0x7b0 [dvb_core] [] ? __schedule+0x343/0x930 [] ? dvb_frontend_release+0x110/0x110 [dvb_core] [] kthread+0x10b/0x130 [] ? sched_clock+0x9/0x10 [] ? kthread_create_on_node+0x250/0x250 [] ret_from_fork+0x7c/0xb0 [] ? kthread_create_on_node+0x250/0x250 Signed-off-by: Antti Palosaari Signed-off-by: Mauro Carvalho Chehab --- drivers/media/dvb-frontends/rtl2832.c | 48 +++++++++++++++++----- drivers/media/dvb-frontends/rtl2832_priv.h | 2 + 2 files changed, 40 insertions(+), 10 deletions(-) diff --git a/drivers/media/dvb-frontends/rtl2832.c b/drivers/media/dvb-frontends/rtl2832.c index eaa74b0c8609..0f2a743bb195 100644 --- a/drivers/media/dvb-frontends/rtl2832.c +++ b/drivers/media/dvb-frontends/rtl2832.c @@ -1028,6 +1028,32 @@ static int rtl2832_regmap_gather_write(void *context, const void *reg, return 0; } +/* + * FIXME: Hack. Implement own regmap locking in order to silence lockdep + * recursive lock warning. That happens when regmap I2C client calls I2C mux + * adapter, which leads demod I2C repeater enable via demod regmap. Operation + * takes two regmap locks recursively - but those are different regmap instances + * in a two different I2C drivers, so it is not deadlock. Proper fix is to make + * regmap aware of lockdep. + */ +static void rtl2832_regmap_lock(void *__dev) +{ + struct rtl2832_dev *dev = __dev; + struct i2c_client *client = dev->client; + + dev_dbg(&client->dev, "\n"); + mutex_lock(&dev->regmap_mutex); +} + +static void rtl2832_regmap_unlock(void *__dev) +{ + struct rtl2832_dev *dev = __dev; + struct i2c_client *client = dev->client; + + dev_dbg(&client->dev, "\n"); + mutex_unlock(&dev->regmap_mutex); +} + static struct dvb_frontend *rtl2832_get_dvb_frontend(struct i2c_client *client) { struct rtl2832_dev *dev = i2c_get_clientdata(client); @@ -1186,15 +1212,6 @@ static int rtl2832_probe(struct i2c_client *client, .range_max = 5 * 0x100, }, }; - static const struct regmap_config regmap_config = { - .reg_bits = 8, - .val_bits = 8, - .volatile_reg = rtl2832_volatile_reg, - .max_register = 5 * 0x100, - .ranges = regmap_range_cfg, - .num_ranges = ARRAY_SIZE(regmap_range_cfg), - .cache_type = REGCACHE_RBTREE, - }; dev_dbg(&client->dev, "\n"); @@ -1213,8 +1230,19 @@ static int rtl2832_probe(struct i2c_client *client, INIT_DELAYED_WORK(&dev->i2c_gate_work, rtl2832_i2c_gate_work); INIT_DELAYED_WORK(&dev->stat_work, rtl2832_stat_work); /* create regmap */ + mutex_init(&dev->regmap_mutex); + dev->regmap_config.reg_bits = 8, + dev->regmap_config.val_bits = 8, + dev->regmap_config.lock = rtl2832_regmap_lock, + dev->regmap_config.unlock = rtl2832_regmap_unlock, + dev->regmap_config.lock_arg = dev, + dev->regmap_config.volatile_reg = rtl2832_volatile_reg, + dev->regmap_config.max_register = 5 * 0x100, + dev->regmap_config.ranges = regmap_range_cfg, + dev->regmap_config.num_ranges = ARRAY_SIZE(regmap_range_cfg), + dev->regmap_config.cache_type = REGCACHE_RBTREE, dev->regmap = regmap_init(&client->dev, ®map_bus, client, - ®map_config); + &dev->regmap_config); if (IS_ERR(dev->regmap)) { ret = PTR_ERR(dev->regmap); goto err_kfree; diff --git a/drivers/media/dvb-frontends/rtl2832_priv.h b/drivers/media/dvb-frontends/rtl2832_priv.h index 9ff4f6530346..c3a922c37903 100644 --- a/drivers/media/dvb-frontends/rtl2832_priv.h +++ b/drivers/media/dvb-frontends/rtl2832_priv.h @@ -33,6 +33,8 @@ struct rtl2832_dev { struct rtl2832_platform_data *pdata; struct i2c_client *client; + struct mutex regmap_mutex; + struct regmap_config regmap_config; struct regmap *regmap; struct i2c_adapter *i2c_adapter_tuner; struct dvb_frontend fe; -- 2.20.1