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Subject[PATCH 5/8] __cpu_up: use singlethreaded workqueue
Currently i386 and x86_64 __cpu_up uses the services of the kevents
workqueue to bring the cpu up. Change this and use kthread workqueue
instead which is single_threaded and won't be frozen during
CPU_HOTPLUG.

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>
--
arch/i386/kernel/smpboot.c | 3 ++-
arch/x86_64/kernel/smpboot.c | 5 +++--
include/linux/kthread.h | 5 +++--
kernel/kthread.c | 16 +++++++++++++---
4 files changed, 21 insertions(+), 8 deletions(-)
Index: linux-2.6.21-rc5/include/linux/kthread.h
===================================================================
--- linux-2.6.21-rc5.orig/include/linux/kthread.h
+++ linux-2.6.21-rc5/include/linux/kthread.h
@@ -3,7 +3,7 @@
/* Simple interface for creating and stopping kernel threads without mess. */
#include <linux/err.h>
#include <linux/sched.h>
-
+#include <linux/workqueue.h>
struct task_struct *kthread_create(int (*threadfn)(void *data),
void *data,
const char namefmt[], ...);
@@ -29,5 +29,6 @@ struct task_struct *kthread_create(int (
void kthread_bind(struct task_struct *k, unsigned int cpu);
int kthread_stop(struct task_struct *k);
int kthread_should_stop(void);
-
+extern void kthreadwq_queue_work(struct work_struct *w);
+extern int kthreadwq_up(void);
#endif /* _LINUX_KTHREAD_H */
Index: linux-2.6.21-rc5/kernel/kthread.c
===================================================================
--- linux-2.6.21-rc5.orig/kernel/kthread.c
+++ linux-2.6.21-rc5/kernel/kthread.c
@@ -112,7 +112,7 @@ static int kthread(void *_create)
return 0;
}

-/* We are keventd: create a thread. */
+/* We are keventd: create a thread. Hmm, Are we?? */
static void keventd_create_kthread(struct work_struct *work)
{
struct kthread_create_info *create =
@@ -132,6 +132,16 @@ static void keventd_create_kthread(struc
complete(&create->done);
}

+void kthreadwq_queue_work(struct work_struct *work)
+{
+ queue_work(helper_wq, work);
+}
+
+int kthreadwq_up()
+{
+ return (helper_wq != NULL);
+}
+
/**
* kthread_create - create a kthread.
* @threadfn: the function to run until signal_pending(current).
@@ -167,10 +177,10 @@ struct task_struct *kthread_create(int (
/*
* The workqueue needs to start up first:
*/
- if (!helper_wq)
+ if (!kthreadwq_up())
create.work.func(&create.work);
else {
- queue_work(helper_wq, &create.work);
+ kthreadwq_queue_work(&create.work);
wait_for_completion(&create.done);
}
if (!IS_ERR(create.result)) {
Index: linux-2.6.21-rc5/arch/i386/kernel/smpboot.c
===================================================================
--- linux-2.6.21-rc5.orig/arch/i386/kernel/smpboot.c
+++ linux-2.6.21-rc5/arch/i386/kernel/smpboot.c
@@ -46,6 +46,7 @@
#include <linux/cpu.h>
#include <linux/percpu.h>
#include <linux/nmi.h>
+#include <linux/kthread.h>

#include <linux/delay.h>
#include <linux/mc146818rtc.h>
@@ -968,7 +969,7 @@ static int __cpuinit __smp_prepare_cpu(i
clone_pgd_range(swapper_pg_dir, swapper_pg_dir + USER_PGD_PTRS,
min_t(unsigned long, KERNEL_PGD_PTRS, USER_PGD_PTRS));
flush_tlb_all();
- schedule_work(&info.task);
+ kthreadwq_queue_work(&info.task);
wait_for_completion(&done);

zap_low_mappings();
Index: linux-2.6.21-rc5/arch/x86_64/kernel/smpboot.c
===================================================================
--- linux-2.6.21-rc5.orig/arch/x86_64/kernel/smpboot.c
+++ linux-2.6.21-rc5/arch/x86_64/kernel/smpboot.c
@@ -50,6 +50,7 @@
#include <linux/mc146818rtc.h>
#include <linux/smp.h>
#include <linux/kdebug.h>
+#include <linux/kthread.h>

#include <asm/mtrr.h>
#include <asm/pgalloc.h>
@@ -613,10 +614,10 @@ static int __cpuinit do_boot_cpu(int cpu
* in context of keventd(), we would end up with locking up the keventd
* thread.
*/
- if (!keventd_up() || current_is_keventd())
+ if (!kthreadwq_up())
c_idle.work.func(&c_idle.work);
else {
- schedule_work(&c_idle.work);
+ kthreadwq_queue_work(&c_idle.work);
wait_for_completion(&c_idle.done);
}

--
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
-
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