Re: [RFC][PATCH] firmware: Drop WARN from usermodehelper_read_trylock error case

[Ming Lei]

On Wed, Apr 29, 2015 at 8:11 AM, Laura Abbott <labbott@xxxxxxxxxxxxxxxxx> wrote:
> We've received a number of reports of warnings when coming
> out of suspend with certain bluetooth firmware configurations:
>
> WARNING: CPU: 3 PID: 3280 at drivers/base/firmware_class.c:1126
> _request_firmware+0x558/0x810()
> Modules linked in: ccm ip6t_rpfilter ip6t_REJECT nf_reject_ipv6
> xt_conntrack ebtable_nat ebtable_broute bridge stp llc ebtable_filter
> ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6
> ip6table_mangle ip6table_security ip6table_raw ip6table_filter
> ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4
> nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw
> binfmt_misc bnep intel_rapl iosf_mbi arc4 x86_pkg_temp_thermal
> snd_hda_codec_hdmi coretemp kvm_intel joydev snd_hda_codec_realtek
> iwldvm snd_hda_codec_generic kvm iTCO_wdt mac80211 iTCO_vendor_support
> snd_hda_intel snd_hda_controller snd_hda_codec crct10dif_pclmul
> snd_hwdep crc32_pclmul snd_seq crc32c_intel ghash_clmulni_intel uvcvideo
> snd_seq_device iwlwifi btusb videobuf2_vmalloc snd_pcm videobuf2_core
>  serio_raw bluetooth cfg80211 videobuf2_memops sdhci_pci v4l2_common
> videodev thinkpad_acpi sdhci i2c_i801 lpc_ich mfd_core wacom mmc_core
> media snd_timer tpm_tis hid_logitech_hidpp wmi tpm rfkill snd mei_me mei
> shpchp soundcore nfsd auth_rpcgss nfs_acl lockd grace sunrpc i915
> i2c_algo_bit drm_kms_helper e1000e drm hid_logitech_dj ptp pps_core
> video
> CPU: 3 PID: 3280 Comm: kworker/u17:0 Not tainted 3.19.3-200.fc21.x86_64
> Hardware name: LENOVO 343522U/343522U, BIOS GCET96WW (2.56 ) 10/22/2013
> Workqueue: hci0 hci_power_on [bluetooth]
>  0000000000000000 0000000089944328 ffff88040acffb78 ffffffff8176e215
>  0000000000000000 0000000000000000 ffff88040acffbb8 ffffffff8109bc1a
>  0000000000000000 ffff88040acffcd0 00000000fffffff5 ffff8804076bac40
> Call Trace:
>  [<ffffffff8176e215>] dump_stack+0x45/0x57
>  [<ffffffff8109bc1a>] warn_slowpath_common+0x8a/0xc0
>  [<ffffffff8109bd4a>] warn_slowpath_null+0x1a/0x20
>  [<ffffffff814dbe78>] _request_firmware+0x558/0x810
>  [<ffffffff814dc165>] request_firmware+0x35/0x50
>  [<ffffffffa03a7886>] btusb_setup_bcm_patchram+0x86/0x590 [btusb]
>  [<ffffffff814d40e6>] ? rpm_idle+0xd6/0x230
>  [<ffffffffa04d4801>] hci_dev_do_open+0xe1/0xa90 [bluetooth]
>  [<ffffffff810c51dd>] ? ttwu_do_activate.constprop.90+0x5d/0x70
>  [<ffffffffa04d5980>] hci_power_on+0x40/0x200 [bluetooth]
>  [<ffffffff810b487c>] process_one_work+0x14c/0x3f0
>  [<ffffffff810b52f3>] worker_thread+0x53/0x470
>  [<ffffffff810b52a0>] ? rescuer_thread+0x300/0x300
>  [<ffffffff810ba548>] kthread+0xd8/0xf0
>  [<ffffffff810ba470>] ? kthread_create_on_node+0x1b0/0x1b0
>  [<ffffffff81774958>] ret_from_fork+0x58/0x90
>  [<ffffffff810ba470>] ? kthread_create_on_node+0x1b0/0x1b0
>
> This occurs after every resume.
>
> When resuming, the bluetooth driver needs to re-request the
> firmware. This re-request is happening before usermodehelper
> is fully enabled. If the firmware load succeeded previously, the
> caching behavior of the firmware code typically negates the
> need to call the usermodehelper code again and the request
> succeeds. If the firmware was never loaded because it isn't
> actually present in the file system, this results in a call
> to usermodehelper and a failure warning every resume. Rather

Yes, it is a driver problem, and loading firmware from filesystem
isn't safe during resume, and that is the purpose of the warning.

> than have a WARN clogging up the kernel messages each time,
> just drop the warn. There is still a dev_err for debugging
> purposes.
>
> Signed-off-by: Laura Abbott <labbott@xxxxxxxxxxxxxxxxx>
> ---
> This might be papering over a real issue but I'm not
> familiar enough with any of suspend/resume, bluetooth,
> or firmware loading to identify an alternate fix.
> The backtrace is from bcm patchram but the problem
> isn't limited to that hardware. Intel also does a
> request firmware and I was able to reproduce the
> same backtrace on that driver by requesting non-existant
> firmware file.
> ---
>  drivers/base/firmware_class.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> index 171841a..48ce9ac 100644
> --- a/drivers/base/firmware_class.c
> +++ b/drivers/base/firmware_class.c
> @@ -1115,7 +1115,7 @@ _request_firmware(const struct firmware **firmware_p, const char *name,
>                 }
>         } else {
>                 ret = usermodehelper_read_trylock();
> -               if (WARN_ON(ret)) {
> +               if (ret) {
>                         dev_err(device, "firmware: %s will not be loaded\n",
>                                 name);
>                         goto out;
> --
> 2.1.0
>
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