On Tue, 2013-01-22 at 13:03 +0530, Srivatsa S. Bhat wrote: > A straight-forward (and obvious) algorithm to implement Per-CPU Reader-Writer > locks can also lead to too many deadlock possibilities which can make it very > hard/impossible to use. This is explained in the example below, which helps > justify the need for a different algorithm to implement flexible Per-CPU > Reader-Writer locks. > > We can use global rwlocks as shown below safely, without fear of deadlocks: > > Readers: > > CPU 0 CPU 1 > ------ ------ > > 1. spin_lock(&random_lock); read_lock(&my_rwlock); > > > 2. read_lock(&my_rwlock); spin_lock(&random_lock); > > > Writer: > > CPU 2: > ------ > > write_lock(&my_rwlock); >
I thought global locks are now fair. That is, a reader will block if a writer is waiting. Hence, the above should deadlock on the current rwlock_t types. We need to fix those locations (or better yet, remove all rwlocks ;-) -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
