Messages in this thread | | | Date | Fri, 21 Nov 2014 12:09:30 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] ipc,sem block sem_lock on sma->lock during sma initialization |
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On Fri, 21 Nov 2014 14:52:26 -0500 Rik van Riel <riel@redhat.com> wrote:
> When manipulating just one semaphore with semop, sem_lock only takes that > single semaphore's lock. This creates a problem during initialization of > the semaphore array, when the data structures used by sem_lock have not > been set up yet. The sma->lock is already held by newary, and we just > have to make sure everything else waits on that lock during initialization. > > Luckily it is easy to make sem_lock wait on the sma->lock, by pretending > there is a complex operation in progress while the sma is being initialized. > > The newary function already zeroes sma->complex_count before unlocking > the sma->lock.
What are the runtime effects of the bug?
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