On Thu, Aug 11, 2005 at 11:56:34AM +0200, Ingo Molnar wrote:
>
> * Paul E. McKenney <[email protected]> wrote:
>
> > Hello!
> >
> > This patch is an experiment in use of RCU for individual code paths
> > that read-acquire the tasklist lock, in this case, unicast signal
> > delivery. It passes five kernbenches on 4-CPU x86, but obviously needs
> > much more testing before it is considered for serious use, let alone
> > inclusion.
> >
> > My main question is whether I have the POSIX semantics covered. I
> > believe that I do, but thought I should check with people who are more
> > familiar with POSIX than am I.
> >
> > For the record, some shortcomings of this patch:
> >
> > o Needs lots more testing on more architectures.
> >
> > o Needs performance and stress testing.
> >
> > o Needs testing in Ingo's PREEMPT_RT environment.
>
> cool patch! I have integrated it into my PREEMPT_RT tree, and all it
> needed to boot was the patch below (doesnt affect the upstream kernel).
> Using the raw IRQ flag isnt an issue in the RCU code, all the affected
> codepaths are small and deterministic.
>
> (without this patch it locked up after detecting IRQ7 - not sure why.)
Without this patch on an older version of PREEMPT_RT (V0.7.52-12),
it would boot, pass kernbench, but fail LTP. Passed both on a stock
kernel.
Will re-run with your patch. ;-)
> kernel still works fine after some (mostly light) testing.
Cool! Next step for me is to run some focussed stress tests.
Thanx, Paul
> Ingo
>
> Index: linux/kernel/rcupdate.c
> ===================================================================
> --- linux.orig/kernel/rcupdate.c
> +++ linux/kernel/rcupdate.c
> @@ -134,11 +134,11 @@ void fastcall call_rcu(struct rcu_head *
>
> head->func = func;
> head->next = NULL;
> - local_irq_save(flags);
> + raw_local_irq_save(flags);
> rdp = &__get_cpu_var(rcu_data);
> *rdp->nxttail = head;
> rdp->nxttail = &head->next;
> - local_irq_restore(flags);
> + raw_local_irq_restore(flags);
> }
>
> /**
> @@ -165,11 +165,11 @@ void fastcall call_rcu_bh(struct rcu_hea
>
> head->func = func;
> head->next = NULL;
> - local_irq_save(flags);
> + raw_local_irq_save(flags);
> rdp = &__get_cpu_var(rcu_bh_data);
> *rdp->nxttail = head;
> rdp->nxttail = &head->next;
> - local_irq_restore(flags);
> + raw_local_irq_restore(flags);
> }
>
> /*
> @@ -305,11 +305,11 @@ static void rcu_check_quiescent_state(st
> static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list,
> struct rcu_head **tail)
> {
> - local_irq_disable();
> + raw_local_irq_disable();
> *this_rdp->nxttail = list;
> if (list)
> this_rdp->nxttail = tail;
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> static void __rcu_offline_cpu(struct rcu_data *this_rdp,
> @@ -362,13 +362,13 @@ static void __rcu_process_callbacks(stru
> rdp->curtail = &rdp->curlist;
> }
>
> - local_irq_disable();
> + raw_local_irq_disable();
> if (rdp->nxtlist && !rdp->curlist) {
> rdp->curlist = rdp->nxtlist;
> rdp->curtail = rdp->nxttail;
> rdp->nxtlist = NULL;
> rdp->nxttail = &rdp->nxtlist;
> - local_irq_enable();
> + raw_local_irq_enable();
>
> /*
> * start the next batch of callbacks
> @@ -388,7 +388,7 @@ static void __rcu_process_callbacks(stru
> spin_unlock(&rsp->lock);
> }
> } else {
> - local_irq_enable();
> + raw_local_irq_enable();
> }
> rcu_check_quiescent_state(rcp, rsp, rdp);
> if (rdp->donelist)
>
-
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