Em Thu, 18 Dec 2014 12:29:46 +0200
Antti Palosaari <crope@xxxxxx> escreveu:
> Introduce own lock to silence locdep warning. I suspect lockdep checks
> make wrong decision when two similar name (&map->mutex) locks were
> taken recursively, even those are different mutexes in a two different
> driver. After that patch, functionality remains same, but mutex names
> are different.
Please do not add a hack just to silence a lockdep warning.
Please take a look at: Documentation/locking/lockdep-design.txt
There are some documentation there about the usage of nested locks and
how to avoid lockdep to complain.
Regards,
Mauro
>
> =============================================
> [ 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: [<ffffffff814ec90f>] regmap_lock_mutex+0x2f/0x40
>
> but task is already holding lock:
> (&map->mutex){+.+.+.}, at: [<ffffffff814ec90f>] 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: [<ffffffff814ec90f>] 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:
> [<ffffffff817a6f82>] dump_stack+0x4e/0x68
> [<ffffffff810e7f94>] __lock_acquire+0x1ea4/0x1f50
> [<ffffffff810e2a7d>] ? trace_hardirqs_off+0xd/0x10
> [<ffffffff817b01f3>] ? _raw_spin_lock_irqsave+0x83/0xa0
> [<ffffffff810e13e6>] ? up+0x16/0x50
> [<ffffffff810e2a7d>] ? trace_hardirqs_off+0xd/0x10
> [<ffffffff817af8bf>] ? _raw_spin_unlock_irqrestore+0x5f/0x70
> [<ffffffff810e9069>] lock_acquire+0xc9/0x170
> [<ffffffff814ec90f>] ? regmap_lock_mutex+0x2f/0x40
> [<ffffffff817ab50e>] mutex_lock_nested+0x7e/0x430
> [<ffffffff814ec90f>] ? regmap_lock_mutex+0x2f/0x40
> [<ffffffff814ec90f>] ? regmap_lock_mutex+0x2f/0x40
> [<ffffffff817a530b>] ? printk+0x70/0x86
> [<ffffffff8110d9e8>] ? mod_timer+0x168/0x240
> [<ffffffff814ec90f>] regmap_lock_mutex+0x2f/0x40
> [<ffffffff814f08d9>] regmap_update_bits+0x29/0x60
> [<ffffffffa03e9778>] rtl2832_select+0x38/0x70 [rtl2832]
> [<ffffffffa039b03d>] i2c_mux_master_xfer+0x3d/0x90 [i2c_mux]
> [<ffffffff815da493>] __i2c_transfer+0x73/0x2e0
> [<ffffffff815dbaba>] i2c_transfer+0x5a/0xc0
> [<ffffffff815dbb6e>] i2c_master_send+0x4e/0x70
> [<ffffffffa03ff25a>] regmap_i2c_write+0x1a/0x50 [regmap_i2c]
> [<ffffffff817ab713>] ? mutex_lock_nested+0x283/0x430
> [<ffffffff814f06b2>] _regmap_raw_write+0x862/0x880
> [<ffffffff814ec90f>] ? regmap_lock_mutex+0x2f/0x40
> [<ffffffff814f0744>] _regmap_bus_raw_write+0x74/0xa0
> [<ffffffff814ef3d2>] _regmap_write+0x92/0x140
> [<ffffffff814f0b7b>] regmap_write+0x4b/0x70
> [<ffffffffa032b090>] ? dvb_frontend_release+0x110/0x110 [dvb_core]
> [<ffffffffa05141d4>] e4000_init+0x34/0x210 [e4000]
> [<ffffffffa032a029>] dvb_frontend_init+0x59/0xc0 [dvb_core]
> [<ffffffff810bde30>] ? finish_task_switch+0x80/0x180
> [<ffffffff810bddf2>] ? finish_task_switch+0x42/0x180
> [<ffffffffa032b116>] dvb_frontend_thread+0x86/0x7b0 [dvb_core]
> [<ffffffff817a9203>] ? __schedule+0x343/0x930
> [<ffffffffa032b090>] ? dvb_frontend_release+0x110/0x110 [dvb_core]
> [<ffffffff810b826b>] kthread+0x10b/0x130
> [<ffffffff81020099>] ? sched_clock+0x9/0x10
> [<ffffffff810b8160>] ? kthread_create_on_node+0x250/0x250
> [<ffffffff817b063c>] ret_from_fork+0x7c/0xb0
> [<ffffffff810b8160>] ? kthread_create_on_node+0x250/0x250
>
> Signed-off-by: Antti Palosaari <crope@xxxxxx>
> ---
> drivers/media/dvb-frontends/rtl2832.c | 49 +++++++++++++++++++++++-------
> drivers/media/dvb-frontends/rtl2832_priv.h | 2 ++
> 2 files changed, 40 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/media/dvb-frontends/rtl2832.c b/drivers/media/dvb-frontends/rtl2832.c
> index f44dc50..2ee5bcf 100644
> --- a/drivers/media/dvb-frontends/rtl2832.c
> +++ b/drivers/media/dvb-frontends/rtl2832.c
> @@ -1028,6 +1028,31 @@ static int rtl2832_regmap_gather_write(void *context, const void *reg,
> return 0;
> }
>
> +/*
> + * FIXME: 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 should be deadlock.
> + */
> +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 +1211,6 @@ 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");
>
> @@ -1218,8 +1234,19 @@ 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;
> @@ -1232,7 +1259,7 @@ static int rtl2832_probe(struct i2c_client *client,
>
> /* create muxed i2c adapter for demod tuner bus */
> dev->i2c_adapter_tuner = i2c_add_mux_adapter(i2c, &i2c->dev, dev,
> - 0, 0, 0, rtl2832_select, rtl2832_deselect);
> + 0, 1, 0, rtl2832_select, rtl2832_deselect);
> if (dev->i2c_adapter_tuner == NULL) {
> ret = -ENODEV;
> goto err_regmap_exit;
> diff --git a/drivers/media/dvb-frontends/rtl2832_priv.h b/drivers/media/dvb-frontends/rtl2832_priv.h
> index 9ff4f65..c3a922c 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;
--
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