[Xen-devel] [PATCH v2 2/2] hotplug: Prevent alloc/free of irq descriptors during cpu up/down (again)

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

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>
Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CC: x86@xxxxxxxxxx
CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 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 2a6e84a..067de61 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1108,17 +1108,8 @@ 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;
        }
@@ -1136,8 +1127,6 @@ 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 341bf80..ec12b72 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -349,8 +349,16 @@ 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;
-- 
2.7.4


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