From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Date: Wed, 21 Mar 2012 17:03:45 +0000 (-0400)
Subject: xen/smp: Fix bringup bug in AP code.
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=106b44388d8f76373149c4ea144f717b6d4d9a6d;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git

xen/smp: Fix bringup bug in AP code.

The CPU hotplug code has now a callback to help bring up the CPU.
Without the call we end up getting:

 BUG: soft lockup - CPU#0 stuck for 29s! [migration/0:6]
Modules linked in:
CPU ] Pid: 6, comm: migration/0 Not tainted 3.3.0upstream-01180-ged378a5 #1 Dell Inc. PowerEdge T105 /0RR825
RIP: e030:[<ffffffff810d3b8b>]  [<ffffffff810d3b8b>] stop_machine_cpu_stop+0x7b/0xf0
RSP: e02b:ffff8800ceaabdb0  EFLAGS: 00000293
.. snip..
Call Trace:
 [<ffffffff810d3b10>] ? stop_one_cpu_nowait+0x50/0x50
 [<ffffffff810d3841>] cpu_stopper_thread+0xf1/0x1c0
 [<ffffffff815a9776>] ? __schedule+0x3c6/0x760
 [<ffffffff815aa749>] ? _raw_spin_unlock_irqrestore+0x19/0x30
 [<ffffffff810d3750>] ? res_counter_charge+0x150/0x150
 [<ffffffff8108dc76>] kthread+0x96/0xa0
 [<ffffffff815b27e4>] kernel_thread_helper+0x4/0x10
 [<ffffffff815aacbc>] ? retint_restore_ar

Thix fixes it.

Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---

diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 449f86897db3..240def438dc3 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -75,8 +75,14 @@ static void __cpuinit cpu_bringup(void)
 
 	xen_setup_cpu_clockevents();
 
+	notify_cpu_starting(cpu);
+
+	ipi_call_lock();
 	set_cpu_online(cpu, true);
+	ipi_call_unlock();
+
 	this_cpu_write(cpu_state, CPU_ONLINE);
+
 	wmb();
 
 	/* We can take interrupts now: we're officially "up". */