Re: rwlock_t unfairness and tasklist_lock

2013-01-24 Thread Michel Lespinasse
On Sat, Jan 12, 2013 at 9:31 AM, Oleg Nesterov wrote: > On 01/09, Michel Lespinasse wrote: >> >> - Would there be any fundamental objection to implementing a fair >> >> rwlock_t and dealing with the reentrancy issues in tasklist_lock ? My >> >> proposal there would be along the lines of: >> > >> >

Re: rwlock_t unfairness and tasklist_lock

2013-01-12 Thread Oleg Nesterov
On 01/09, Michel Lespinasse wrote: > > On Wed, Jan 9, 2013 at 9:49 AM, Oleg Nesterov wrote: > > On 01/08, Michel Lespinasse wrote: > >> Like others before me, I have discovered how easy it is to DOS a > >> system by abusing the rwlock_t unfairness and causing the > >> tasklist_lock read side to be

Re: rwlock_t unfairness and tasklist_lock

2013-01-11 Thread Thomas Gleixner
On Tue, 8 Jan 2013, Michel Lespinasse wrote: > - Does anyone know of any current work towards removing the > tasklist_lock use of rwlock_t ? Thomas Gleixner mentioned 3 years ago > that he'd give it a shot (https://lwn.net/Articles/364601/), did he > encounter some unforeseen difficulty that we sho

Re: rwlock_t unfairness and tasklist_lock

2013-01-09 Thread Michel Lespinasse
On Wed, Jan 9, 2013 at 9:49 AM, Oleg Nesterov wrote: > On 01/08, Michel Lespinasse wrote: >> Like others before me, I have discovered how easy it is to DOS a >> system by abusing the rwlock_t unfairness and causing the >> tasklist_lock read side to be continuously held > > Yes. Plus it has perfoma

Re: rwlock_t unfairness and tasklist_lock

2013-01-09 Thread Oleg Nesterov
On 01/08, Michel Lespinasse wrote: > > Like others before me, I have discovered how easy it is to DOS a > system by abusing the rwlock_t unfairness and causing the > tasklist_lock read side to be continuously held Yes. Plus it has perfomance problems. It should die. We still need the global lock