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| author | Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> | 2013-06-03 16:33:55 +0200 |
|---|---|---|
| committer | Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> | 2013-06-04 15:03:18 +0200 |
| commit | 466318a87f28cb3ba0d08a3b7ef1a37ae73d5aa7 (patch) | |
| tree | 81e405945646a47f6cd6c17f7389f733d15fe30b /arch/x86/xen/smp.c | |
| parent | xenbus_client.c: correct exit path for xenbus_map_ring_valloc_hvm (diff) | |
| download | linux-466318a87f28cb3ba0d08a3b7ef1a37ae73d5aa7.tar.xz linux-466318a87f28cb3ba0d08a3b7ef1a37ae73d5aa7.zip | |
xen/smp: Fixup NOHZ per cpu data when onlining an offline CPU.
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.
CC: stable@vger.kernel.org
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'arch/x86/xen/smp.c')
| -rw-r--r-- | arch/x86/xen/smp.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c index fb44426fe931..d99cae8147d1 100644 --- 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> @@ -447,6 +448,13 @@ static void __cpuinit xen_play_dead(void) /* used only with HOTPLUG_CPU */ 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 */ |