summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorMaksim Rayskiy <mrayskiy@broadcom.com>2011-02-12 10:21:32 -0800
committerRalf Baechle <ralf@linux-mips.org>2011-03-14 21:07:27 +0100
commit6667deb69ee3b8a31ea88e1303cf3ad7d4f221da (patch)
tree575e660bec3cdb905f31940ab3ca64d7185202be
parentba9786f32473410bbec256db9745a7fbcaace69f (diff)
downloadkernel-6667deb69ee3b8a31ea88e1303cf3ad7d4f221da.tar.gz
MIPS: Move idle task creation to work queue
To avoid forking usermode thread when creating an idle task, move fork_idle to a work queue. If kernel starts with maxcpus= option which does not bring all available cpus online at boot time, idle tasks for offline cpus are not created. If later offline cpus are hotplugged through sysfs, __cpu_up is called in the context of the user task, and fork_idle copies its non-zero mm pointer. This causes BUG() in per_cpu_trap_init. This also avoids issues with resource limits of the CPU writing to sysfs, containers, maybe others. Signed-off-by: Maksim Rayskiy <mrayskiy@broadcom.com> To: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/2070/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
-rw-r--r--arch/mips/kernel/smp.c31
1 files changed, 29 insertions, 2 deletions
diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index 383aeb95cb49..32a256101082 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -193,6 +193,22 @@ 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;
@@ -203,8 +219,19 @@ 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 arch/x86/kernel/smpboot.c
+ */
+ 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);