[PATCH] x86: cpu_init(): avoid GFP_KERNEL allocation while atomic

The patch fixes two issues:

1.  cpu_init is called with interrupt disabled.  Allocating gdt table
   there isn't good at runtime.

2. gdt table page cause memory leak in CPU hotplug case.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/cpu/common.c

@@ -613,6 +613,12 @@ void __cpuinit cpu_init(void)
 		set_in_cr4(X86_CR4_TSD);
 	}
 
+	/* The CPU hotplug case */
+	if (cpu_gdt_descr->address) {
+		gdt = (struct desc_struct *)cpu_gdt_descr->address;
+		memset(gdt, 0, PAGE_SIZE);
+		goto old_gdt;
+	}
 	/*
 	 * This is a horrible hack to allocate the GDT.  The problem
 	 * is that cpu_init() is called really early for the boot CPU
@@ -631,7 +637,7 @@ void __cpuinit cpu_init(void)
 				local_irq_enable();
 		}
 	}
-
+old_gdt:
 	/*
 	 * Initialize the per-CPU GDT with the boot GDT,
 	 * and set up the GDT descriptor:

arch/i386/kernel/smpboot.c

@@ -1056,6 +1056,7 @@ static int __cpuinit __smp_prepare_cpu(int cpu)
 	struct warm_boot_cpu_info info;
 	struct work_struct task;
 	int	apicid, ret;
+	struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
 
 	apicid = x86_cpu_to_apicid[cpu];
 	if (apicid == BAD_APICID) {
@@ -1063,6 +1064,18 @@ static int __cpuinit __smp_prepare_cpu(int cpu)
 		goto exit;
 	}
 
+	/*
+	 * the CPU isn't initialized at boot time, allocate gdt table here.
+	 * cpu_init will initialize it
+	 */
+	if (!cpu_gdt_descr->address) {
+		cpu_gdt_descr->address = get_zeroed_page(GFP_KERNEL);
+		if (!cpu_gdt_descr->address)
+			printk(KERN_CRIT "CPU%d failed to allocate GDT\n", cpu);
+			ret = -ENOMEM;
+			goto exit;
+	}
+
 	info.complete = &done;
 	info.apicid = apicid;
 	info.cpu = cpu;