Re: [PATCH] usb: typec: fusb302: Call fusb302_debugfs_init earlier

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

On Thu, Aug 15, 2019 at 02:54:41PM +0200, Greg Kroah-Hartman wrote:
> On Tue, Aug 13, 2019 at 01:52:16PM +0300, Heikki Krogerus wrote:
> > Hi Hans,
> > 
> > On Tue, Aug 13, 2019 at 12:15:24PM +0200, Hans de Goede wrote:
> > > tcpm_register_port() will call some of the fusb302 code's callbacks
> > > wich in turn will call fusb302_log(). So we need to call
> > > fusb302_debugfs_init() before we call tcpm_register_port().
> > > 
> > > This fixes the following warning, which was caused by the logbuffer_lock
> > > not yet being initialized (which is done by fusb302_debugfs_init):
> > > 
> > >  DEBUG_LOCKS_WARN_ON(lock->magic != lock)
> > >  WARNING: CPU: 0 PID: 1306 at kernel/locking/mutex.c:912 __mutex_lock+0x978/0x9a0
> > >  Modules linked in: fusb302(+) tcpm pi3usb30532 typec bq24190_charger snd_soc_sst_cht_bsw_rt5645 mei_hdcp dwc3 intel_rapl_msr udc_core ulpi gpio_keys intel_powerclamp coretemp kvm_intel brcmfmac kvm brcmutil joydev cfg80211 wdat_wdt irqbypass pcspkr intel_cstate extcon_intel_cht_wc i2c_cht_wc(E) snd_intel_sst_acpi snd_intel_sst_core snd_soc_rt5645 snd_soc_sst_atom_hifi2_platform snd_soc_acpi_intel_match snd_soc_rl6231 snd_soc_acpi intel_xhci_usb_role_switch roles hci_uart snd_soc_core btqca mei_txe btrtl processor_thermal_device mei snd_hdmi_lpe_audio lpc_ich snd_compress btbcm intel_rapl_common ac97_bus dwc3_pci snd_pcm_dmaengine intel_soc_dts_iosf btintel snd_seq bluetooth snd_seq_device snd_pcm intel_cht_int33fe_musb snd_timer intel_cht_int33fe_typec intel_hid intel_cht_int33fe_common sparse_keymap snd ecdh_generic goodix rfkill soundcore ecc spi_pxa2xx_platform max17042_battery dw_dmac int3406_thermal dptf_power acpi_pad soc_button_array int3400_thermal int3403_thermal
> > >   gpd_pocket_fan intel_int0002_vgpio int340x_thermal_zone acpi_thermal_rel dm_crypt mmc_block i915 crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel i2c_algo_bit drm_kms_helper drm video sdhci_acpi sdhci mmc_core pwm_lpss_platform pwm_lpss i2c_dev
> > >  CPU: 0 PID: 1306 Comm: systemd-udevd Tainted: G            E     5.3.0-rc4+ #83
> > >  Hardware name: Default string Default string/Default string, BIOS 5.11 06/28/2017
> > >  RIP: 0010:__mutex_lock+0x978/0x9a0
> > >  Code: c0 0f 84 26 f7 ff ff 44 8b 05 24 25 c8 00 45 85 c0 0f 85 16 f7 ff ff 48 c7 c6 da 55 2f ae 48 c7 c7 98 8c 2d ae e8 a0 f9 5c ff <0f> 0b e9 fc f6 ff ff 4c 89 f0 4d 89 fe 49 89 c7 e9 cf fa ff ff e8
> > >  RSP: 0018:ffffb7a8c0523800 EFLAGS: 00010286
> > >  RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> > >  RDX: 0000000000000002 RSI: 0000000000000001 RDI: 0000000000000246
> > >  RBP: ffffb7a8c05238c0 R08: 0000000000000000 R09: 0000000000000000
> > >  R10: ffffb7a8c0523648 R11: 0000000000000030 R12: 0000000000000000
> > >  R13: ffffb7a8c0523990 R14: ffff9bf22f70c028 R15: ffff9bf22f70c360
> > >  FS:  00007f39ca234940(0000) GS:ffff9bf237400000(0000) knlGS:0000000000000000
> > >  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > >  CR2: 00007f1f108481a0 CR3: 0000000271f28000 CR4: 00000000001006f0
> > >  Call Trace:
> > >   ? find_held_lock+0x39/0x90
> > >   ? _fusb302_log+0x81/0x1d0 [fusb302]
> > >   ? vsnprintf+0x3aa/0x4f0
> > >   ? _fusb302_log+0x81/0x1d0 [fusb302]
> > >   _fusb302_log+0x81/0x1d0 [fusb302]
> > >  ...
> > > 
> > > Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> > > ---
> > >  drivers/usb/typec/tcpm/fusb302.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/usb/typec/tcpm/fusb302.c b/drivers/usb/typec/tcpm/fusb302.c
> > > index ccfc7e91e7a3..04c76b9d0065 100644
> > > --- a/drivers/usb/typec/tcpm/fusb302.c
> > > +++ b/drivers/usb/typec/tcpm/fusb302.c
> > > @@ -1759,6 +1759,7 @@ static int fusb302_probe(struct i2c_client *client,
> > >  	INIT_WORK(&chip->irq_work, fusb302_irq_work);
> > >  	INIT_DELAYED_WORK(&chip->bc_lvl_handler, fusb302_bc_lvl_handler_work);
> > >  	init_tcpc_dev(&chip->tcpc_dev);
> > > +	fusb302_debugfs_init(chip);
> > >  
> > >  	if (client->irq) {
> > >  		chip->gpio_int_n_irq = client->irq;
> > > @@ -1784,7 +1785,6 @@ static int fusb302_probe(struct i2c_client *client,
> > >  		goto tcpm_unregister_port;
> > >  	}
> > >  	enable_irq_wake(chip->gpio_int_n_irq);
> > > -	fusb302_debugfs_init(chip);
> > >  	i2c_set_clientdata(client, chip);
> > 
> > That leaves the rootdir variable pointing to something again for
> > example if a failure happens (like -EPROBE_AGAIN) during probe (the
> > "fusb302" directory is removed, but the rootdir static variable still
> > points to something).
> > 
> > Let's just create that rootdir directory during driver init. I don't
> > really understand why should we only create it when/if the first
> > instance of fusb302 is registered. I think something like this would
> > work:
> > 
> > diff --git a/drivers/usb/typec/tcpm/fusb302.c b/drivers/usb/typec/tcpm/fusb302.c
> > index c524088246ee..7a950a6e5f0d 100644
> > --- a/drivers/usb/typec/tcpm/fusb302.c
> > +++ b/drivers/usb/typec/tcpm/fusb302.c
> > @@ -212,9 +212,6 @@ static struct dentry *rootdir;
> >  static void fusb302_debugfs_init(struct fusb302_chip *chip)
> >  {
> >         mutex_init(&chip->logbuffer_lock);
> > -       if (!rootdir)
> > -               rootdir = debugfs_create_dir("fusb302", NULL);
> > -
> >         chip->dentry = debugfs_create_file(dev_name(chip->dev),
> >                                            S_IFREG | 0444, rootdir,
> >                                            chip, &fusb302_debug_fops);
> > @@ -223,7 +220,6 @@ static void fusb302_debugfs_init(struct fusb302_chip *chip)
> >  static void fusb302_debugfs_exit(struct fusb302_chip *chip)
> >  {
> >         debugfs_remove(chip->dentry);
> > -       debugfs_remove(rootdir);
> >  }
> >  
> >  #else
> > @@ -1863,7 +1859,24 @@ static struct i2c_driver fusb302_driver = {
> >         .remove = fusb302_remove,
> >         .id_table = fusb302_i2c_device_id,
> >  };
> > -module_i2c_driver(fusb302_driver);
> > +
> > +static int __init fusb302_init(void)
> > +{
> > +       rootdir = debugfs_create_dir("fusb302", NULL);
> > +       if (IS_ERR(rootdir))
> > +               return PTR_ERR(rootdir);
> 
> As Guenter points out, don't check this, just call it anb move on.
> 
> But are you _SURE_ you want this to be the name, at the root of debugfs?
> Why not put it under the usb debugfs directory?

That's a good point. Let's move it there while at it.

thanks,

-- 
heikki