cpu/hotplug: Prevent alloc/free of irq descriptors during CPU up/down (again)

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@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: david.vrabel@citrix.com
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1470244948-17674-3-git-send-email-boris.ostrovsky@oracle.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 8 insertions, 11 deletions

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 2a6e84a30a54..067de612d3fa 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 341bf80f80bd..ec12b726fa6f 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;