From: Maksim Rayskiy <mrayskiy@xxxxxxxxxxxx>
To avoid forking usertask when creating an idle task, move fork_idle
to a work queue.
This is a small improvement to previous commit 467f0b8.
Signed-off-by: Maksim Rayskiy <mrayskiy@xxxxxxxxxxxx>
---
Ralf, this is per your suggestion. The code is mostly copy-pasted
from arch/x86/kernel/smpboot.c
arch/mips/kernel/smp.c | 32 ++++++++++++++++++++++++++------
1 files changed, 26 insertions(+), 6 deletions(-)
diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index 4593916..98bd504 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -193,6 +193,21 @@ void __devinit smp_prepare_boot_cpu(void)
*/
static struct task_struct *cpu_idle_thread[NR_CPUS];
+struct create_idle {
+ struct work_struct work;
+ struct task_struct *idle;
+ struct completion done;
+ int cpu;
+};
+
+static void __cpuinit do_fork_idle(struct work_struct *work)
+{
+ struct create_idle *c_idle =
+ container_of(work, struct create_idle, work);
+ c_idle->idle = fork_idle(c_idle->cpu);
+ complete(&c_idle->done);
+}
+
int __cpuinit __cpu_up(unsigned int cpu)
{
struct task_struct *idle;
@@ -203,16 +218,21 @@ int __cpuinit __cpu_up(unsigned int cpu)
* Linux can schedule processes on this slave.
*/
if (!cpu_idle_thread[cpu]) {
- idle = fork_idle(cpu);
- cpu_idle_thread[cpu] = idle;
+ /* Schedule work item to avoid forking user task.
+ Ported from x86 */
+ struct create_idle c_idle = {
+ .cpu = cpu,
+ .done = COMPLETION_INITIALIZER_ONSTACK(c_idle.done),
+ };
+
+ INIT_WORK_ONSTACK(&c_idle.work, do_fork_idle);
+ schedule_work(&c_idle.work);
+ wait_for_completion(&c_idle.done);
+ idle = cpu_idle_thread[cpu] = c_idle.idle;
if (IS_ERR(idle))
panic(KERN_ERR "Fork failed for CPU %d", cpu);
- if (idle->mm) {
- mmput(idle->mm);
- idle->mm = NULL;
- }
} else {
idle = cpu_idle_thread[cpu];
init_idle(idle, cpu);
--
1.7.3.2
