On 9 August 2017 at 03:29, Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> wrote:
> Hi
>
> On 2017/8/9 7:48, Michał Mirosław wrote:
>>
>> Fix lockdep splat introduced in v4.13-rc4.
>>
>> [ 266.297226] ------------[ cut here ]------------
>> [ 266.300078] WARNING: CPU: 2 PID: 176 at
>> /mnt/src/jaja/git/tf300t/include/linux/blkdev.h:657
>> mmc_blk_remove_req+0xd0/0xe8 [mmc_block]
>> [ 266.302937] Modules linked in: mmc_block(-) sdhci_tegra sdhci_pltfm
>> sdhci pwrseq_simple pwrseq_emmc mmc_core
>> [ 266.305941] CPU: 2 PID: 176 Comm: rmmod Tainted: G W
>> 4.13.0-rc4mq-00208-gb691e67724b8-dirty #694
>> [ 266.308852] Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
>> [ 266.311719] [<b011144c>] (unwind_backtrace) from [<b010ca54>]
>> (show_stack+0x18/0x1c)
>> [ 266.314664] [<b010ca54>] (show_stack) from [<b062e3f4>]
>> (dump_stack+0x84/0x98)
>> [ 266.317644] [<b062e3f4>] (dump_stack) from [<b01214f4>]
>> (__warn+0xf4/0x10c)
>> [ 266.320542] [<b01214f4>] (__warn) from [<b01215d4>]
>> (warn_slowpath_null+0x28/0x30)
>> [ 266.323534] [<b01215d4>] (warn_slowpath_null) from [<af067858>]
>> (mmc_blk_remove_req+0xd0/0xe8 [mmc_block])
>> [ 266.326568] [<af067858>] (mmc_blk_remove_req [mmc_block]) from
>> [<af068f40>] (mmc_blk_remove_parts.constprop.6+0x50/0x64 [mmc_block])
>> [ 266.329678] [<af068f40>] (mmc_blk_remove_parts.constprop.6 [mmc_block])
>> from [<af0693b8>] (mmc_blk_remove+0x24/0x140 [mmc_block])
>> [ 266.332894] [<af0693b8>] (mmc_blk_remove [mmc_block]) from [<af0052ec>]
>> (mmc_bus_remove+0x20/0x28 [mmc_core])
>> [ 266.336198] [<af0052ec>] (mmc_bus_remove [mmc_core]) from [<b046aa64>]
>> (device_release_driver_internal+0x164/0x200)
>> [ 266.339367] [<b046aa64>] (device_release_driver_internal) from
>> [<b046ab54>] (driver_detach+0x40/0x74)
>> [ 266.342537] [<b046ab54>] (driver_detach) from [<b046982c>]
>> (bus_remove_driver+0x68/0xdc)
>> [ 266.345660] [<b046982c>] (bus_remove_driver) from [<af06ad40>]
>> (mmc_blk_exit+0xc/0x2cc [mmc_block])
>> [ 266.348875] [<af06ad40>] (mmc_blk_exit [mmc_block]) from [<b01aee30>]
>> (SyS_delete_module+0x1c4/0x254)
>> [ 266.352068] [<b01aee30>] (SyS_delete_module) from [<b0108480>]
>> (ret_fast_syscall+0x0/0x34)
>> [ 266.355308] ---[ end trace f68728a0d3053b72 ]---
>>
>
>
> Ouch... 7c84b8b43d3d *also* races the q->bypass_depth with blk layer, so
> in principle, QUEUE_FLAG_BYPASS shouldn't be used outside the blk layer.
> However we have to use it when we couldn't do these within
> blk_cleanup_queue..
As quick fix, this will have to do.
However, to me this clearly shows that we need to continue the
re-factorization and convert to blkmq asap. While doing that, we must
also make sure to smoke out all the odd things that goes on in the
current mmc block/queue code related to hotplug.
>
> My current system couldn't boot with a modular mmc-blk, so i can't test
> this case but obvious the race and lockdep case is here. Great to find
> this fatal mistake, mea culpa.
>
> Reviewed-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
>
>
>
>> Fixes: 7c84b8b43d3d ("mmc: block: bypass the queue even if usage is
>> present for hotplug")
>> Signed-off-by: Michał Mirosław <mirq-linux@xxxxxxxxxxxx>
Applied for fixes!
Thanks both of you for looking into this and fixing the problem!
Kind regards
Uffe
>> ---
>> drivers/mmc/core/block.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
>> index e5938c791330..f1bbfd389367 100644
>> --- a/drivers/mmc/core/block.c
>> +++ b/drivers/mmc/core/block.c
>> @@ -2170,7 +2170,9 @@ static void mmc_blk_remove_req(struct mmc_blk_data
>> *md)
>> * from being accepted.
>> */
>> card = md->queue.card;
>> + spin_lock_irq(md->queue.queue->queue_lock);
>> queue_flag_set(QUEUE_FLAG_BYPASS, md->queue.queue);
>> + spin_unlock_irq(md->queue.queue->queue_lock);
>> blk_set_queue_dying(md->queue.queue);
>> mmc_cleanup_queue(&md->queue);
>> if (md->disk->flags & GENHD_FL_UP) {
>>
>
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