On Thursday 05 January 2006 23:27, Jeff Dike wrote:
> On Thu, Jan 05, 2006 at 08:54:37PM +0100, Blaisorblade wrote:
> > Meanwhile, the whole content of the new free_winch(), including some
> > syscalls on the host, and various other stuff, is brought back under the
> > winch_handler_lock.
>
> And? There's no particular problem with host system calls being under
> a lock. And the various other stuff is a kfree and a free_irq, which
> I don't think have a problem being called under a spinlock.
Indeed, right. Ok, no real objections on the patch.
> > I had carefully brought that stuff out keeping only the list access under
> > the lock, probably while fixing some "scheduling while atomic" warnings -
> > once the element is out of the list it's unreachable thus (IMHO) safely
> > accessible.
>
> Probably? What in there is sensitive to being called under a lock?
Ok, sorry, wrong here. I remembered doing the thing but it was for other
reasons - reducing spinlock hold times. Doing syscalls under spinlocks is
just (possibly) slow, not wrong. But ok, the commendment was "thou shalt not
optimize".
> > So, list_del should be brought out from free_winch, which would then
> > become callable without the spinlock held.
> That would increase the amount of code, with no gain that I can see.
> The list_del would be duplicated, and the loop in winch_cleanup would
> have to drop and reacquire the lock around each call to free_winch.
I thought mainly to unregister_winch(); the lock in winch_cleanup() has been
added now, I didn't see it.
> Jeff
--
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade
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