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SubjectRe: 174cc7187e6f ACPICA: Tables: Back port acpi_get_table_with_size() and early_acpi_os_unmap_memory() from Linux kernel
On Mon, Jan 09, 2017 at 03:32:04PM -0800, Paul E. McKenney wrote:
> We could move rcu_scheduler_starting() later, as long as there
> is no chance of preemption or context switch before it is invoked.
> Would that help in this case, or are we already context switching before
> acpi_os_map_cleanup() is invoked? (If we are already context switching,
> short-circuiting synchronize_rcu_expedited() would be a bug.)

Hmm, how about the below?

It would still happen before

/*
* The boot idle thread must execute schedule()
* at least once to get things moving:
*/
init_idle_bootup_task(current);
schedule_preempt_disabled();

in rest_init() and right after native_smp_prepare_cpus() which is where
we're splatting.

Lemme run it.

Even if it works, we would have to stress-test this seriously...

---
diff --git a/init/main.c b/init/main.c
index b0c9d6facef9..9be221cc87c3 100644
--- a/init/main.c
+++ b/init/main.c
@@ -385,7 +385,6 @@ static noinline void __ref rest_init(void)
{
int pid;

- rcu_scheduler_starting();
/*
* We need to spawn init first so that it obtains pid 1, however
* the init task will end up wanting to create kthreads, which, if
@@ -1019,6 +1018,8 @@ static noinline void __init kernel_init_freeable(void)

smp_prepare_cpus(setup_max_cpus);

+ rcu_scheduler_starting();
+
workqueue_init();

do_pre_smp_initcalls();

--
Regards/Gruss,
Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

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