I'm intermittently hitting this warning on 4.7.0:

    /* We can't free more than one frame at once on a shared queue */
    WARN_ON(!iwl_mvm_is_dqa_supported(mvm) && (skb_freed > 1));

I'm seeing this on 4.7 with firmware 16.242414.0 and with 21.302800.0.  I haven't tried older firmware versions.  I don't recall seeing anything like this on older kernels.

The bootup messages look like:

[  +0.000103] iwlwifi 0000:3a:00.0: enabling device (0000 -> 0002)
[  +0.001245] iwlwifi 0000:3a:00.0: Unsupported splx structure
[  +0.004160] iwlwifi 0000:3a:00.0: loaded firmware version 21.302800.0 op_mode iwlmvm
[  +0.194856] iwlwifi 0000:3a:00.0: Detected Intel(R) Dual Band Wireless AC 7265, REV=0x210
[  +0.001457] iwlwifi 0000:3a:00.0: L1 Enabled - LTR Disabled
[  +0.000208] iwlwifi 0000:3a:00.0: L1 Enabled - LTR Disabled



Here's the full trace:

[  230.077849] ------------[ cut here ]------------
[  230.077908] WARNING: CPU: 0 PID: 953 at drivers/net/wireless/intel/iwlwifi/mvm/tx.c:1377 iwl_mvm_rx_tx_cmd+0x665/0x870 [iwlmvm]
[  230.077916] Modules linked in: rfcomm fuse xt_CHECKSUM ipt_MASQUERADE nf_nat_masquerade_ipv4 tun nf_conntrack_netbios_ns nf_conntrack_broadcast ip6t_REJECT nf_reject_ipv6 xt_conntrack ip6t_rpfilter ebtable_nat ebtable_broute bridge stp llc ip6table_mangle ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_security ip6table_raw iptable_mangle iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_security iptable_raw ebtable_filter ebtables ip6table_filter ip6_tables cmac bnep arc4 vfat fat iwlmvm mac80211 snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic iwlwifi snd_hda_intel hid_multitouch snd_hda_codec intel_rapl x86_pkg_temp_thermal coretemp btusb kvm_intel btrtl snd_hwdep cfg80211 btbcm uvcvideo snd_hda_core btintel kvm bluetooth snd_seq
[  230.078100]  videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_core i2c_designware_platform videodev snd_seq_device iTCO_wdt iTCO_vendor_support i2c_designware_core snd_pcm dell_wmi dell_laptop dell_smbios rtsx_pci_ms snd_timer dcdbas memstick snd mei_me media efi_pstore irqbypass mei pcspkr joydev i2c_i801 rfkill efivars soundcore shpchp idma64 intel_lpss_pci processor_thermal_device intel_soc_dts_iosf wmi pinctrl_sunrisepoint acpi_als pinctrl_intel tpm_tis intel_lpss_acpi kfifo_buf int3403_thermal int340x_thermal_zone industrialio intel_lpss intel_hid tpm int3400_thermal acpi_pad acpi_thermal_rel sparse_keymap nfsd auth_rpcgss nfs_acl lockd grace sunrpc binfmt_misc dm_crypt i915 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops rtsx_pci_sdmmc drm mmc_core crct10dif_pclmul
[  230.078300]  crc32_pclmul crc32c_intel ghash_clmulni_intel rtsx_pci serio_raw i2c_hid video i2c_dev
[  230.078335] CPU: 0 PID: 953 Comm: irq/284-iwlwifi Not tainted 4.7.0-xps13+ #113
[  230.078344] Hardware name: Dell Inc. XPS 13 9350/07TYC2, BIOS 1.4.4 06/14/2016
[  230.078353]  0000000000000286 0000000001b64962 ffff88026e46fbb0 ffffffff81462534
[  230.078373]  0000000000000000 0000000000000000 ffff88026e46fbf0 ffffffff81097a4b
[  230.078389]  0000056172b70720 0000000000000000 0000000000000c9a 0000000000000c9a
[  230.078405] Call Trace:
[  230.078426]  [<ffffffff81462534>] dump_stack+0x65/0x91
[  230.078439]  [<ffffffff81097a4b>] __warn+0xcb/0xf0
[  230.078453]  [<ffffffff81097b7d>] warn_slowpath_null+0x1d/0x20
[  230.078496]  [<ffffffffa08ed2e5>] iwl_mvm_rx_tx_cmd+0x665/0x870 [iwlmvm]
[  230.078512]  [<ffffffff810dbd54>] ? __wake_up+0x44/0x50
[  230.078550]  [<ffffffffa08e3605>] iwl_mvm_rx_common+0x165/0x260 [iwlmvm]
[  230.078584]  [<ffffffffa08e375b>] iwl_mvm_rx+0x5b/0x70 [iwlmvm]
[  230.078620]  [<ffffffffa07c7979>] iwl_pcie_rx_handle+0x319/0x950 [iwlwifi]
[  230.078659]  [<ffffffffa07c93cb>] iwl_pcie_irq_handler+0x4db/0xb10 [iwlwifi]
[  230.078673]  [<ffffffff810f51c0>] ? irq_forced_thread_fn+0x70/0x70
[  230.078685]  [<ffffffff810f51e0>] irq_thread_fn+0x20/0x50
[  230.078698]  [<ffffffff810f54ad>] irq_thread+0x12d/0x1c0
[  230.078715]  [<ffffffff81887773>] ? __schedule+0x2f3/0x7b0
[  230.078728]  [<ffffffff810f52d0>] ? wake_threads_waitq+0x30/0x30
[  230.078740]  [<ffffffff810f5380>] ? irq_thread_dtor+0xb0/0xb0
[  230.078756]  [<ffffffff810b7808>] kthread+0xd8/0xf0
[  230.078773]  [<ffffffff8188c7bf>] ret_from_fork+0x1f/0x40
[  230.078789]  [<ffffffff810b7730>] ? kthread_worker_fn+0x160/0x160
[  230.078823] ---[ end trace d3fe05c9ae367e3f ]---
[  230.078909] ------------[ cut here ]------------