On Thursday 21 August 2008, Jared Hulbert wrote: > > Have you seen any benefit of the rwsem over a simple mutex? I would guess > > that you can never even get into the situation where you get concurrent > > readers since I haven't found a single down_read() in your code, only > > downgrade_write() > > We implemented a rwsem here because you can get concurrent readers. > My understanding is that downgrade_write() puts the rewem into the > same state as down_read(). Am I mistaken? Your interpretation of downgrade_write is correct, but if every thread always does down_write(); serialized_code(); downgrade_write(); parallel_code(); up_read(); Then you still won't have any concurrency, because each thread trying to down_write() will be blocked until the previous one has done its up_read(), causing parallel_code() to be serialized as well. In addition to that, I'd still consider it better to use a simple mutex if parallel_code() is a much faster operation than serialized_code(), as it is in your case, where only the memcpy is parallel and that is much slower than the deflate. Arnd <>< -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
