Messages in this thread | | | Subject | Re: RT and Cascade interrupts | From | Trond Myklebust <> | Date | Sat, 28 May 2005 13:35:57 -0700 |
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lau den 28.05.2005 Klokka 13:48 (-0400) skreiv john cooper:
> The other possibility to fix the original problem within > the scope of the RPC code was to replace the bit state of > RPC_TASK_HAS_TIMER with a count so we don't obscure the > fact the timer was requeued during the preemption window. > This happens as rpc_run_timer() does an unconditional > clear_bit(RPC_TASK_HAS_TIMER,..) before returning. > > Another would be to check timer->base/timer_pending() > in rpc_run_timer() and to omit doing a clear_bit() > if the timer is found to have been requeued.
Could you please explain why you think such a scenario is possible? The timer functions themselves should never be causing a re-queue, and every iteration through the loop in __rpc_execute() should cause any pending timer to be killed, as should rpc_release_task().
That's why we can use del_singleshot_timer_sync() in the first place: because there is no recursion, and no re-queueing that can cause races. I don't see how either preemption or RT will change that (and if they do, then _that_ is the real bug that needs fixing).
Cheers, Trond
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