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Commit deef3250 authored by Ingo Molnar's avatar Ingo Molnar Committed by Thomas Gleixner
Browse files

x86: disable preemption in native_smp_prepare_cpus 



Priit Laes reported the following warning:

Call Trace:
 [<ffffffff8022f1e1>] warn_on_slowpath+0x51/0x63
 [<ffffffff80282e48>] sys_ioctl+0x2d/0x5d
 [<ffffffff805185ff>] _spin_lock+0xe/0x24
 [<ffffffff80227459>] task_rq_lock+0x3d/0x73
 [<ffffffff805133c3>] set_cpu_sibling_map+0x336/0x350
 [<ffffffff8021c1b8>] read_apic_id+0x30/0x62
 [<ffffffff806d921d>] verify_local_APIC+0x90/0x138
 [<ffffffff806d84b5>] native_smp_prepare_cpus+0x1f9/0x305
 [<ffffffff806ce7b1>] kernel_init+0x59/0x2d9
 [<ffffffff80518a26>] _spin_unlock_irq+0x11/0x2b
 [<ffffffff8020bf48>] child_rip+0xa/0x12
 [<ffffffff806ce758>] kernel_init+0x0/0x2d9
 [<ffffffff8020bf3e>] child_rip+0x0/0x12

fix this by generally disabling preemption in native_smp_prepare_cpus().

Reported-and-bisected-by: default avatarPriit Laes <plaes@plaes.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent fb3bbd6a

arch/x86/kernel/smpboot.c

+4 −1
Original line number Diff line number Diff line
@@ -1190,6 +1190,7 @@ static void __init smp_cpu_index_default(void) 
 */

void __init native_smp_prepare_cpus(unsigned int max_cpus)

{

	preempt_disable();

	nmi_watchdog_default();

	smp_cpu_index_default();

	current_cpu_data = boot_cpu_data;
@@ -1206,7 +1207,7 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus) 
	if (smp_sanity_check(max_cpus) < 0) {

		printk(KERN_INFO "SMP disabled\n");

		disable_smp();

		return;

		goto out;

	}



	preempt_disable();
@@ -1246,6 +1247,8 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus) 
	printk(KERN_INFO "CPU%d: ", 0);

	print_cpu_info(&cpu_data(0));

	setup_boot_clock();

out:

	preempt_enable();

}

/*

 * Early setup to make printk work.