Re: [PATCH] mlx4: prevent the device from being removed concurrently

From: Thadeu Lima de Souza Cascardo <redacted>
Date: Tue, 28 Feb 2012 17:34:38 -0300

On Tue, Feb 28, 2012 at 02:30:51PM -0500, David Miller wrote:

quoted

From: Thadeu Lima de Souza Cascardo <redacted>
Date: Tue, 28 Feb 2012 15:36:16 -0300

quoted

When a EEH happens, the catas poll code will try to restart the device,
removing it and adding it back again. The EEH code will try to do the
same. One of the threads ends up accessing memory that was freed by the
other thread and we get a crash.

Stop adding bandaids to the locking.

If the EEH infrastructure doesn't synchronize parallel operations
on the same device, that is the real bug, and that's where the real
fix belongs.

I refuse to apply this patch.

It's not EEH that does not synchronize removal. The problem is that the
driver itself calls the driver remove function through mlx4_restart_one.

Then reuse the existing intf_mutex this driver has, export it to
main.c and add a new __mlx4_unregister_device that can be called
with the intf_mutex held already.
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