Is it supposed to be ok to call del_gendisk while userspace isfrozen?

[Maxim Levitsky]

I noticed that currently calling del_gendisk leads to sure deadlock if
attemped from .suspend or .resume functions.

Something like that:

[<ffffffff8106620a>] ? prepare_to_wait+0x2a/0x90
[<ffffffff810790bd>] ? trace_hardirqs_on+0xd/0x10
[<ffffffff8140db12>] ? _raw_spin_unlock_irqrestore+0x42/0x80
[<ffffffff8112a390>] ? bdi_sched_wait+0x0/0x20
[<ffffffff8112a39e>] bdi_sched_wait+0xe/0x20
[<ffffffff8140af6f>] __wait_on_bit+0x5f/0x90
[<ffffffff8112a390>] ? bdi_sched_wait+0x0/0x20
[<ffffffff8140b018>] out_of_line_wait_on_bit+0x78/0x90
[<ffffffff81065fd0>] ? wake_bit_function+0x0/0x40
[<ffffffff8112a2d3>] ? bdi_queue_work+0xa3/0xe0
[<ffffffff8112a37f>] bdi_sync_writeback+0x6f/0x80
[<ffffffff8112a3d2>] sync_inodes_sb+0x22/0x120
[<ffffffff8112f1d2>] __sync_filesystem+0x82/0x90
[<ffffffff8112f3db>] sync_filesystem+0x4b/0x70
[<ffffffff811391de>] fsync_bdev+0x2e/0x60
[<ffffffff812226be>] invalidate_partition+0x2e/0x50
[<ffffffff8116b92f>] del_gendisk+0x3f/0x140
[<ffffffffa00c0233>] mmc_blk_remove+0x33/0x60 [mmc_block]
[<ffffffff81338977>] mmc_bus_remove+0x17/0x20
[<ffffffff812ce746>] __device_release_driver+0x66/0xc0
[<ffffffff812ce89d>] device_release_driver+0x2d/0x40
[<ffffffff812cd9b5>] bus_remove_device+0xb5/0x120
[<ffffffff812cb46f>] device_del+0x12f/0x1a0
[<ffffffff81338a5b>] mmc_remove_card+0x5b/0x90
[<ffffffff8133ac27>] mmc_sd_remove+0x27/0x50
[<ffffffff81337d8c>] mmc_resume_host+0x10c/0x140
[<ffffffffa00850e9>] sdhci_resume_host+0x69/0xa0 [sdhci]
[<ffffffffa0bdc39e>] sdhci_pci_resume+0x8e/0xb0 [sdhci_pci]

bdi_queue_work seems to be the problem.

Some device drivers need to remove their cards logically in .suspend,
because the card is removable, and can be changed while system is
suspended.

Best regards,
Maxim Levitsky

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