Messages in this thread | | | Date | Wed, 17 Oct 2018 17:11:34 +0200 | From | Andrea Parri <> | Subject | Re: [PATCH 2/4] fscache: Fix race in fscache_op_complete() due to split atomic_sub & read |
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Hi David,
On Wed, Oct 17, 2018 at 03:23:38PM +0100, David Howells wrote: > From: kiran.modukuri <kiran.modukuri@gmail.com> > > The code in fscache_retrieval_complete is using atomic_sub followed by an > atomic_read: > > atomic_sub(n_pages, &op->n_pages); > if (atomic_read(&op->n_pages) <= 0) > fscache_op_complete(&op->op, true); > > This causes two threads doing a decrement of n_pages to race with each > other seeing the op->refcount 0 at same time - and they end up calling > fscache_op_complete() in both the threads leading to an assertion failure. > > Fix this by using atomic_sub_return() instead of two calls.
Seems a case for atomic_sub_return_relaxed()... why not?
Andrea
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