This is a note to let you know that I've just added the patch titled
xen/smp: Fixup NOHZ per cpu data when onlining an offline CPU.
to the 3.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xen-smp-fixup-nohz-per-cpu-data-when-onlining-an-offline-cpu.patch
and it can be found in the queue-3.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 466318a87f28cb3ba0d08a3b7ef1a37ae73d5aa7 Mon Sep 17 00:00:00 2001
From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Date: Mon, 3 Jun 2013 10:33:55 -0400
Subject: xen/smp: Fixup NOHZ per cpu data when onlining an offline CPU.
From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
commit 466318a87f28cb3ba0d08a3b7ef1a37ae73d5aa7 upstream.
The xen_play_dead is an undead function. When the vCPU is told to
offline it ends up calling xen_play_dead wherin it calls the
VCPUOP_down hypercall which offlines the vCPU. However, when the
vCPU is onlined back, it resumes execution right after
VCPUOP_down hypercall.
That was OK (albeit the API for play_dead assumes that the CPU
stays dead and never returns) but with commit 4b0c0f294
(tick: Cleanup NOHZ per cpu data on cpu down) that is no longer safe
as said commit resets the ts->inidle which at the start of the
cpu_idle loop was set.
The net effect is that we get this warn:
Broke affinity for irq 16
installing Xen timer for CPU 1
cpu 1 spinlock event irq 48
------------[ cut here ]------------
WARNING: at /home/konrad/linux-linus/kernel/time/tick-sched.c:935 tick_nohz_idle_exit+0x195/0x1b0()
Modules linked in: dm_multipath dm_mod xen_evtchn iscsi_boot_sysfs
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 3.10.0-rc3upstream-00068-gdcdbe33 #1
Hardware name: BIOSTAR Group N61PB-M2S/N61PB-M2S, BIOS 6.00 PG 09/03/2009
ffffffff8193b448 ffff880039da5e60 ffffffff816707c8 ffff880039da5ea0
ffffffff8108ce8b ffff880039da4010 ffff88003fa8e500 ffff880039da4010
0000000000000001 ffff880039da4000 ffff880039da4010 ffff880039da5eb0
Call Trace:
[<ffffffff816707c8>] dump_stack+0x19/0x1b
[<ffffffff8108ce8b>] warn_slowpath_common+0x6b/0xa0
[<ffffffff8108ced5>] warn_slowpath_null+0x15/0x20
[<ffffffff810e4745>] tick_nohz_idle_exit+0x195/0x1b0
[<ffffffff810da755>] cpu_startup_entry+0x205/0x250
[<ffffffff81661070>] cpu_bringup_and_idle+0x13/0x15
---[ end trace 915c8c486004dda1 ]---
b/c ts_inidle is set to zero. Thomas suggested that we just add a workaround
to call tick_nohz_idle_enter before returning from xen_play_dead() - and
that is what this patch does and fixes the issue.
We also add the stable part b/c git commit 4b0c0f294 is on the stable
tree.
Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
arch/x86/xen/smp.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -17,6 +17,7 @@
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/irq_work.h>
+#include <linux/tick.h>
#include <asm/paravirt.h>
#include <asm/desc.h>
@@ -436,6 +437,13 @@ static void __cpuinit xen_play_dead(void
play_dead_common();
HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
cpu_bringup();
+ /*
+ * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
+ * clears certain data that the cpu_idle loop (which called us
+ * and that we return from) expects. The only way to get that
+ * data back is to call:
+ */
+ tick_nohz_idle_enter();
}
#else /* !CONFIG_HOTPLUG_CPU */
Patches currently in stable-queue which might be from konrad.wilk@xxxxxxxxxx are
queue-3.9/xen-smp-fixup-nohz-per-cpu-data-when-onlining-an-offline-cpu.patch
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html