On 02/11/2013 06:11 PM, David Howells wrote: > Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx> wrote: > >> 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); > > The lock order on CPU 0 is unsafe if CPU2 can do: > > write_lock(&my_rwlock); > spin_lock(&random_lock); > > and on CPU 1 if CPU2 can do: > > spin_lock(&random_lock); > write_lock(&my_rwlock); > Right.. > I presume you were specifically excluding these situations? > Yes.. Those cases are simple to find out and fix (by changing the lock ordering). My main problem was with CPU 0 and CPU 1 as shown above.. ... and using a global rwlock helps ease that part out. Regards, Srivatsa S. Bhat -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
