On Wednesday 31 October 2012 00:00:56 Ming Lei wrote:

On Tue, Oct 30, 2012 at 11:38 PM, Alan Stern [off-list ref] wrote:

quoted

Okay, I see your point.  But acquiring the lock here doesn't solve the
problem.  Suppose a thread is about to reset a USB mass-storage device.
It acquires the lock and sees that the noio flag is clear.  But before
it can issue the reset, another thread sets the noio flag.

If the USB mass-storage device is being reseted, the flag should be set
already generally.  If the flag is still unset, that means the disk/network
device isn't added into system(or removed just now), so memory allocation
with block I/O should be allowed during the reset. Looks it isn't one problem,
isn't it?

I am afraid it is, because a disk may just have been probed as the deviceis being reset.

	Regards
		Oliver