]> git.proxmox.com Git - mirror_ubuntu-eoan-kernel.git/commit
usb-storage: fix freezing of the scanning thread
authorAlan Stern <stern@rowland.harvard.edu>
Tue, 21 Feb 2012 18:16:32 +0000 (13:16 -0500)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 22 Feb 2012 00:29:15 +0000 (16:29 -0800)
commitbb94a406682770a35305daaa241ccdb7cab399de
treea6801c8edec8809e34c34ec889db4682f074c923
parent9a9a71b77c3fd511e5dda6236deb8a02d156b864
usb-storage: fix freezing of the scanning thread

This patch (as1521b) fixes the interaction between usb-storage's
scanning thread and the freezer.  The current implementation has a
race: If the device is unplugged shortly after being plugged in and
just as a system sleep begins, the scanning thread may get frozen
before the khubd task.  Khubd won't be able to freeze until the
disconnect processing is complete, and the disconnect processing can't
proceed until the scanning thread finishes, so the sleep transition
will fail.

The implementation in the 3.2 kernel suffers from an additional
problem.  There the scanning thread calls set_freezable_with_signal(),
and the signals sent by the freezer will mess up the thread's I/O
delays, which are all interruptible.

The solution to both problems is the same: Replace the kernel thread
used for scanning with a delayed-work routine on the system freezable
work queue.  Freezable work queues have the nice property that you can
cancel a work item even while the work queue is frozen, and no signals
are needed.

The 3.2 version of this patch solves the problem in Bugzilla #42730.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
CC: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/usb/storage/usb.c
drivers/usb/storage/usb.h