Missed the description on that one. Here it is: We're shortly going to need to be able to block new mnt_writers for long periods of time during a superblock remount operation. Since this operation can sleep, we can not use a spinlock. We opt for a mutex instead.
This are very, very rarely contented, mostly because they are per-cpu. So, this should be very close to as fast as the spinlocks just with the added benefit that we can sleep while holding them. We also need to change the get_cpu_var() to use __get_cpu_var() so that we don't disable preemption. Otherwise, we'll be in_atomic() when we try to lock the (sleepable) mutex. We only use the per-cpu data for cache benefits and its per-cpuness is not part of locking logic, so this is OK. _ -- Dave -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
