Re: [PATCH] fs: Fix mod_timer crash when removing USB sticks

[Josh Boyer]

On Thu, Jan 12, 2012 at 4:15 PM, Paul Taysom <taysom@xxxxxxxxxxxx> wrote:
> From: Paul Taysom <taysom@xxxxxxxxxx>
>
> A USB stick with a ext file system on it, would occasionally crash
> when the stick was pulled.
>
> The problem was a timer was being set on the Backing Device Interface,
> bdi, after the USB device had been removed and the bdi had been
> unregistered. The bdi would then be later reinitialized by zeroing
> the timer without removing from the timer from the timer queue.
> This would eventually result in a kernel crash (NULL ptr dereference).

What backtrace did you see when it crashed?  There have been a number of
reports where sd_revalidate_disk is at the top of the backtrace and this sounds
like it might be related.

josh
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