Messages in this thread |  | | Date | Tue, 11 Feb 2014 15:20:01 +0200 | Subject | Re: Memory allocator semantics | From | Pekka Enberg <> |
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On Tue, Feb 11, 2014 at 2:14 PM, Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote: > In contrast, from kfree() to a kmalloc() returning some of the kfree()ed > memory, I believe the kfree()/kmalloc() implementation must do any needed > synchronization and ordering. But that is a different set of examples, > for example, this one: > > CPU 0 CPU 1 > p->a = 42; q = kmalloc(...); /* returning p */ > kfree(p); q->a = 5; > BUG_ON(q->a != 5); > > Unlike the situation with (A), (B), and (C), in this case I believe > that it is kfree()'s and kmalloc()'s responsibility to ensure that > the BUG_ON() never triggers. > > Make sense?
I'm not sure...
It's the caller's responsibility not to touch "p" after it's handed over to kfree() - otherwise that's a "use-after-free" error. If there's some reordering going on here, I'm tempted to blame the caller for lack of locking.
Pekka
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