Description of problem:
Well, this will be hard to reproduce.
So, I have this microSDXC card where I store some music I'm listening to in my phone. The phone is deleting the songs time to time, I have no idea why at all.
Today, it stopped playing the music completely, getting stuck at "checking the card for errors". I got fed up with this and inserted the card into my laptop to format it.
I'm not sure when exactly this oops happened but it was either when I tried to mount the card, unmount it, open it in gparted or when I just simply ran mkfs.vfat on it.
I'm sorry but I can't provide any more information and I'm afraid I won't be able to reproduce it any more.

Additional info:
WARNING: at drivers/mmc/host/sdhci.c:837 sdhci_send_command+0xa90/0xd70 [sdhci]()
Hardware name: 4243BQ9
Modules linked in: xfs btrfs zlib_deflate libcrc32c vfat fat mmc_block usb_storage fuse ebtable_nat xt_CHECKSUM bridge stp llc ipt_MASQUERADE nf_conntrack_netbios_ns nf_conntrack_broadcast ip6table_mangle ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 iptable_nat nf_nat_ipv4 nf_nat iptable_mangle nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ebtable_filter ebtables ip6table_filter ip6_tables rfcomm be2iscsi bnep iscsi_boot_sysfs bnx2i cnic uio cxgb4i cxgb4 cxgb3i cxgb3 mdio libcxgbi ib_iser rdma_cm ib_addr iw_cm ib_cm ib_sa ib_mad ib_core iscsi_tcp lm75 libiscsi_tcp libiscsi scsi_transport_iscsi dm_crypt arc4 iwldvm mac80211 snd_hda_codec_hdmi snd_hda_codec_conexant iTCO_wdt iTCO_vendor_support coretemp snd_hda_intel snd_hda_codec microcode snd_hwdep snd_seq snd_seq_device snd_pcm i2c_i801 lpc_ich mfd_core uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_core btusb iwlwifi videodev bluetooth media snd_page_alloc cfg80211 snd_timer e1000e mei thinkpad_acpi snd soundcore rfkill vhost_net tun macvtap macvlan kvm_intel kvm uinput nfsd auth_rpcgss nfs_acl lockd sunrpc binfmt_misc i915 firewire_ohci firewire_core crc_itu_t i2c_algo_bit drm_kms_helper sdhci_pci sdhci drm mmc_core crc32c_intel ghash_clmulni_intel i2c_core wmi video
Pid: 21664, comm: mmcqd/0 Not tainted 3.8.4-202.fc18.x86_64 #1
Call Trace:
 [<ffffffff8105e62f>] warn_slowpath_common+0x7f/0xc0
 [<ffffffff8105e68a>] warn_slowpath_null+0x1a/0x20
 [<ffffffffa00c9460>] sdhci_send_command+0xa90/0xd70 [sdhci]
 [<ffffffff813f7289>] ? __pm_runtime_resume+0x69/0x90
 [<ffffffffa00cac46>] sdhci_request+0xd6/0x1dc [sdhci]
 [<ffffffffa004b5da>] __mmc_start_req+0x16a/0x2c0 [mmc_core]
 [<ffffffffa004c846>] mmc_start_req+0x1a6/0x1d0 [mmc_core]
 [<ffffffffa086c4c4>] mmc_blk_issue_rw_rq+0xa4/0x3c0 [mmc_block]
 [<ffffffff810940c0>] ? try_to_wake_up+0x2d0/0x2d0
 [<ffffffffa086cb0b>] mmc_blk_issue_rq+0x1bb/0x4f0 [mmc_block]
 [<ffffffff812d7f53>] ? blk_start_request+0x33/0x50
 [<ffffffffa086dcdd>] mmc_queue_thread+0x5d/0x150 [mmc_block]
 [<ffffffffa086dc80>] ? mmc_alloc_sg+0x70/0x70 [mmc_block]
 [<ffffffff81081fb0>] kthread+0xc0/0xd0
 [<ffffffff81010000>] ? ftrace_define_fields_xen_mc_entry+0xa0/0xf0
 [<ffffffff81081ef0>] ? kthread_create_on_node+0x120/0x120
 [<ffffffff8165882c>] ret_from_fork+0x7c/0xb0
 [<ffffffff81081ef0>] ? kthread_create_on_node+0x120/0x120