Il 23/05/2014 12:37, Bart Van Assche ha scritto:
On 05/23/14 11:24, Paolo Bonzini wrote:
Il 23/05/2014 08:09, Hannes Reinecke ha scritto:
And when freeing a command we absolutely need to make sure that
the workqueue is empty.
So calling cancel_delayed_work() was the obvious thing to do.
You would need cancel_delayed_work_sync, but if it really happened that
the work item is running, it would cause a double free.
I'd be fine with adding a WARN_ON(!list_empty(&cmd->abort_work))
here, however. This will clear up the intent of this statement.
BUG_ON even, since you'd get badness from the double free anyway.
Hello Paolo,
Are you aware that Linus strongly prefers WARN_ON_ONCE() over BUG_ON() ?
See e.g. https://lkml.org/lkml/2012/9/27/461 or
https://lkml.org/lkml/2014/4/28/657.
Yes, I am and I even downgraded some KVM BUG_ONs recently.
But in this case I think that memory corruption is going to happen
anyway unless you consciously leak the Scsi_Cmnd * (because if you use
WARN_ON, you also need to return early as Linus suggested in the second
email).
So the WARN_ON/BUG_ON choice here should not just consider what makes
the problem easier to debug; hanging the machine before guaranteed
badness seems to me like a good use for BUG_ON.
Paolo
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