[PATCH] Fix microcode-related suspend problem

Fix the regression resulting from the recent change of suspend code
ordering that causes systems based on Intel x86 CPUs using the microcode
driver to hang during the resume.

The problem occurs since the microcode driver uses request_firmware() in
its CPU hotplug notifier, which is called after tasks has been frozen and
hangs.  It can be fixed by telling the microcode driver to use the
microcode stored in memory during the resume instead of trying to load it
from disk.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Adrian Bunk <bunk@stusta.de>
Cc: Tigran Aivazian <tigran@aivazian.fsnet.co.uk>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Maxim <maximlevitsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 16 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 3d4206ada5c9..36e70845cfc3 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -254,6 +254,12 @@ int __cpuinit cpu_up(unsigned int cpu)
 }
 
 #ifdef CONFIG_SUSPEND_SMP
+/* Needed to prevent the microcode driver from requesting firmware in its CPU
+ * hotplug notifier during the suspend/resume.
+ */
+int suspend_cpu_hotplug;
+EXPORT_SYMBOL(suspend_cpu_hotplug);
+
 static cpumask_t frozen_cpus;
 
 int disable_nonboot_cpus(void)
@@ -261,16 +267,8 @@ int disable_nonboot_cpus(void)
         int cpu, first_cpu, error = 0;
 
         mutex_lock(&cpu_add_remove_lock);
-        first_cpu = first_cpu(cpu_present_map);
-        if (!cpu_online(first_cpu)) {
-                error = _cpu_up(first_cpu);
-                if (error) {
-                        printk(KERN_ERR "Could not bring CPU%d up.\n",
-                                first_cpu);
-                        goto out;
-                }
-        }
-
+        suspend_cpu_hotplug = 1;
+        first_cpu = first_cpu(cpu_online_map);
         /* We take down all of the non-boot CPUs in one shot to avoid races
          * with the userspace trying to use the CPU hotplug at the same time
          */
@@ -296,7 +294,7 @@ int disable_nonboot_cpus(void)
         } else {
                 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
         }
-out:
+        suspend_cpu_hotplug = 0;
         mutex_unlock(&cpu_add_remove_lock);
         return error;
 }
@@ -308,20 +306,22 @@ void enable_nonboot_cpus(void)
         /* Allow everyone to use the CPU hotplug again */
         mutex_lock(&cpu_add_remove_lock);
         cpu_hotplug_disabled = 0;
-        mutex_unlock(&cpu_add_remove_lock);
         if (cpus_empty(frozen_cpus))
-                return;
+                goto out;
 
+        suspend_cpu_hotplug = 1;
         printk("Enabling non-boot CPUs ...\n");
         for_each_cpu_mask(cpu, frozen_cpus) {
-                error = cpu_up(cpu);
+                error = _cpu_up(cpu);
                 if (!error) {
                         printk("CPU%d is up\n", cpu);
                         continue;
                 }
-                printk(KERN_WARNING "Error taking CPU%d up: %d\n",
-                        cpu, error);
+                printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
         }
         cpus_clear(frozen_cpus);
+        suspend_cpu_hotplug = 0;
+out:
+        mutex_unlock(&cpu_add_remove_lock);
 }
 #endif