Re: proposed smp_rendezvous change

[Andriy Gapon]

on 13/05/2011 17:41 Max Laier said the following:
> this ncpus isn't the one you are looking for.

Thank you!

Here's an updated patch:

Index: sys/kern/subr_smp.c
===================================================================
--- sys/kern/subr_smp.c (revision 221835)
+++ sys/kern/subr_smp.c (working copy)
@@ -316,19 +316,14 @@
        void (*local_action_func)(void*)   = smp_rv_action_func;
        void (*local_teardown_func)(void*) = smp_rv_teardown_func;

-       /* Ensure we have up-to-date values. */
-       atomic_add_acq_int(&smp_rv_waiters[0], 1);
-       while (smp_rv_waiters[0] < smp_rv_ncpus)
-               cpu_spinwait();
-
        /* setup function */
        if (local_setup_func != smp_no_rendevous_barrier) {
                if (smp_rv_setup_func != NULL)
                        smp_rv_setup_func(smp_rv_func_arg);

                /* spin on entry rendezvous */
-               atomic_add_int(&smp_rv_waiters[1], 1);
-               while (smp_rv_waiters[1] < smp_rv_ncpus)
+               atomic_add_int(&smp_rv_waiters[0], 1);
+               while (smp_rv_waiters[0] < smp_rv_ncpus)
                        cpu_spinwait();
        }

@@ -337,12 +332,16 @@
                local_action_func(local_func_arg);

        /* spin on exit rendezvous */
-       atomic_add_int(&smp_rv_waiters[2], 1);
-       if (local_teardown_func == smp_no_rendevous_barrier)
+       atomic_add_int(&smp_rv_waiters[1], 1);
+       if (local_teardown_func == smp_no_rendevous_barrier) {
+               atomic_add_int(&smp_rv_waiters[2], 1);
                 return;
-       while (smp_rv_waiters[2] < smp_rv_ncpus)
+       }
+       while (smp_rv_waiters[1] < smp_rv_ncpus)
                cpu_spinwait();

+       atomic_add_int(&smp_rv_waiters[2], 1);
+
        /* teardown function */
        if (local_teardown_func != NULL)
                local_teardown_func(local_func_arg);
@@ -377,6 +376,10 @@
        /* obtain rendezvous lock */
        mtx_lock_spin(&smp_ipi_mtx);

+       /* Wait for any previous unwaited rendezvous to finish. */
+       while (atomic_load_acq_int(&smp_rv_waiters[2]) < smp_rv_ncpus)
+               cpu_spinwait();
+
        /* set static function pointers */
        smp_rv_ncpus = ncpus;
        smp_rv_setup_func = setup_func;
@@ -395,7 +398,7 @@
                smp_rendezvous_action();

        if (teardown_func == smp_no_rendevous_barrier)
-               while (atomic_load_acq_int(&smp_rv_waiters[2]) < ncpus)
+               while (atomic_load_acq_int(&smp_rv_waiters[1]) < ncpus)
                        cpu_spinwait();

        /* release lock */
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