On Wed, Nov 17, 2010 at 12:30:59PM +0100, Johnny Billquist wrote: > > There are obviously a lot of calls to mutex_enter and mutex_exit with > spin mutexes...
Indeed there are. I don't underestand what Matt said about this. When I was converting /dev/crypto to mutexes I am pretty sure it was explained to me that the _spin forms of the calls were simply optimizations for when the programmer knew the mutex to be a spin mutex due to the IPL at which it was declared. That is, I had a a pile of driver code full of mutex_enter and mutex_exit which were on a high-IPL mutex and I simply converted it all to mutex_spin_enter and mutex_spin_exit with qsubst. Perhaps the rule is that if you take the mutex with spin_enter you must release it with spin_exit. That would make some sense. But I'd love some clarity on this point. > Also a fair number of calls to mutex_spin_exit with the spin lock not > appearing to be held (I actually set and clear a bit to indicate if the > mutex is held, in addition to bumping the IPL). This *does* seem like a bug. -- Thor Lancelot Simon t...@rek.tjls.com "We cannot usually in social life pursue a single value or a single moral aim, untroubled by the need to compromise with others." - H.L.A. Hart
