Messages in this thread | | | Date | Thu, 23 Nov 2006 12:56:00 +0300 | From | Pavel Emelianov <> | Subject | Re: [ckrm-tech] [PATCH 4/13] BC: context handling |
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Paul Menage wrote: > On 11/23/06, Pavel Emelianov <xemul@openvz.org> wrote: >> You mean moving is like this: >> >> old_bc = task->real_bc; >> task->real_bc = new_bc; >> cmpxchg(&tsk->exec_bc, old_bc, new_bc); >> >> ? Then this won't work: >> >> Initialisation: >> current->exec_bc = init_bc; >> current->real_bc = init_bc; >> ... >> IRQ: >> current->exec_bc = init_bc; >> ... >> old_bc = tsk->real_bc; /* init_bc */ >> tsk->real_bc = bc1; >> cx(tsk->exec_bc, init_bc, bc1); /* ok */ >> ... >> Here at the middle of an interrupt >> we have bc1 set as exec_bc on task >> which IS wrong! > > You could get round that by having a separate "irq_bc" that's never > valid for a task not in an interrupt.
No no no. This is not what is needed. You see, we do have to set exec_bc as temporary (and atomic) context. Having temporary context is 1. flexible 2. needed by beancounters' network accountig. We have to track this particular scenario.
Moreover making get_exec_bc() as if (in_interrupt()) return &irq_bc; else return current->exec_bc; is awful. It must me simple and stupid to allow us making temporary contexts in any place of code.
Maybe we can make smth similar to wait_task_inactive and change it's beancounter before unlocking the runqueue?
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