Messages in this thread | | | Date | Sat, 13 Apr 2013 14:10:11 -0700 | Subject | Re: [PATCH] module: Fix race condition between load and unload module | From | Anatol Pomozov <> |
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Hi
On Sat, Apr 13, 2013 at 10:53 AM, Linus Torvalds <torvalds@linux-foundation.org> wrote: > On Sat, Apr 13, 2013 at 8:41 AM, Anatol Pomozov > <anatol.pomozov@gmail.com> wrote: >> >> Does it make sense to move it to a separate function in kref.h? >> >> /** Useful when kref_get is racing with kref_put and refcounter might be 0 */ >> int kref_get_not_zero(kref* ref) { >> return atomic_inc_not_zero(&kref->refcount); >> } > > It turns out we have that, except it's called "unless_zero", because > it uses "atomic_add_unless(x,1,0)", rather than the simplified > "atomic_inc_not_zero(x)". > >> or maybe instead change default behavior of kref_get() to >> atomic_inc_not_zero and force callers check the return value from >> kref_get()? > > That would be painful, and _most_ users should have a preexisting > refcount. So it's probably better in the long run to just keep the > warning (but perhaps fix it to be SMP-safe). So I think the part of > your patch that made kref_get() use atomic_inc_return() is probably a > good idea regardless. > > Also, I changed my patch to be minimal, and not change other users of > kobject_get(). So other users (not kset_find_obj()) will continue to > get the warning, and kset_find_obj() uses the safe version. Looks good to me.
> So this is > what I'm planning on committing as the minimal patch and marking for > stable. The rest (including that atomic_inc_return() in kref_get) > would be cleanup. > > Can you give this a quick test?
I ran the test case for ~60 minutes with XFS tests in parallel - no any issues.
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