[PATCH 2/2] hotplug: Prevent alloc/free of irq descriptors during cpu up/down (again)

From: Boris Ostrovsky
Date: Thu Mar 17 2016 - 09:36:09 EST


Now that Xen no longer allocates irqs in _cpu_up() we can restore
commit a89941816726 ("hotplug: Prevent alloc/free of irq descriptors
during cpu up/down")

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
arch/x86/kernel/smpboot.c | 11 -----------
kernel/cpu.c | 8 ++++++++
2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 643dbdc..cabe21e 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1083,17 +1083,8 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)

common_cpu_up(cpu, tidle);

- /*
- * We have to walk the irq descriptors to setup the vector
- * space for the cpu which comes online. Prevent irq
- * alloc/free across the bringup.
- */
- irq_lock_sparse();
-
err = do_boot_cpu(apicid, cpu, tidle);
-
if (err) {
- irq_unlock_sparse();
pr_err("do_boot_cpu failed(%d) to wakeup CPU#%u\n", err, cpu);
return -EIO;
}
@@ -1111,8 +1102,6 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)
touch_nmi_watchdog();
}

- irq_unlock_sparse();
-
return 0;
}

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 6ea42e8..2ff63b3 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -342,8 +342,16 @@ static int bringup_cpu(unsigned int cpu)
struct task_struct *idle = idle_thread_get(cpu);
int ret;

+ /*
+ * Some architectures have to walk the irq descriptors to
+ * setup the vector space for the cpu which comes online.
+ * Prevent irq alloc/free across the bringup.
+ */
+ irq_lock_sparse();
+
/* Arch-specific enabling code. */
ret = __cpu_up(cpu, idle);
+ irq_unlock_sparse();
if (ret) {
cpu_notify(CPU_UP_CANCELED, cpu);
return ret;
--
1.7.1