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SubjectRe: [RESEND][PATCH-2.6.24-rc8] Fix fakephp deadlock
On 23/01/08 17:46, Greg KH wrote:
> On Tue, Jan 22, 2008 at 02:28:08PM +0000, Ian Abbott wrote:
>> #include <linux/init.h>
>> #include <linux/string.h>
>> #include <linux/slab.h>
>> +#include <linux/workqueue.h>
>> #include "../pci.h"
>> #if !defined(MODULE)
>> @@ -63,10 +64,13 @@ struct dummy_slot {
>> struct list_head node;
>> struct hotplug_slot *slot;
>> struct pci_dev *dev;
>> + struct work_struct remove_work;
>> + unsigned long removed;
>
> You are treating "removed" as an atomic value, so why not just make it
> an atomic_t?

Because I'm using it as a boolean?

> And what is protecting the fact that the flag could be set right after
> it gets checked? I don't see a lock here :)

Okay, it looks like there might be a race condition between
enable_slot() and disable_slot() if some other task calls disable_slot()
while enable_slot() is between the test_bit() and flush_workqueue()
calls. I can fix that by avoiding the call to flush_workqueue() in
enable_slot() and allocating and queueing a work queue item to defer the
call to pci_rescan(). And enable_slot() won't then need to check if the
slot was marked as removed - it can just go ahead and allocate and queue
a work item.

--
-=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@mev.co.uk> )=-
-=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=-


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