On Friday 27 of August 2010 16:52:31 Hedi Berriche wrote: > On Fri, Aug 27, 2010 at 15:40 Petr Tesarik wrote: > | On Friday 27 of August 2010 16:31:35 Hedi Berriche wrote: > | > That said, I'm letting my already over 36 hours run carry on chewing > | > CPU time, and see if it will eventually trip the same problem seen with > | > 4-byte ticket locks. > | > | Hm, this doesn't sound like a viable approach. Since the siglock gets > | initialized to 0 when a new process is started, it may never actually > | wrap around. > | > | I would rather attach a SystemTap probe somewhere during process fork and > | add a bias to the siglock. That should work fine. Let me knock up the > | SystemTap script... > > That would be nice. Ta! Here it is. I don't have a system with the old 64-bit ticket spinlocks at hand, so this is completely untested, but it should work fine. Adjust if needed. Petr
/* Bias the spin lock on fork */ %{ #define LOCK_BIAS ((1ULL << 32) - (1ULL << 15)) %} function bias_siglock (task:long) %{ struct task_struct *tsk = (struct task_struct*)THIS->task; tsk->sighand->siglock.raw_lock.lock = LOCK_BIAS + (LOCK_BIAS << 32); %} function is_err (value:long) %{ THIS->__retvalue = IS_ERR_VALUE((unsigned long)THIS->value); %} probe kernel.function("copy_process").return { if (!is_err($return)) bias_siglock($return); }