3.6.11.6 stable review patch. If anyone has any objections, please let me know. ------------------ From: Konrad Rzeszutek Wilk [ Upstream commit 466318a87f28cb3ba0d08a3b7ef1a37ae73d5aa7 ] 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: [] dump_stack+0x19/0x1b [] warn_slowpath_common+0x6b/0xa0 [] warn_slowpath_null+0x15/0x20 [] tick_nohz_idle_exit+0x195/0x1b0 [] cpu_startup_entry+0x205/0x250 [] 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 Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Steven Rostedt --- arch/x86/xen/smp.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c index 641c91e..76bce6e 100644 --- a/arch/x86/xen/smp.c +++ b/arch/x86/xen/smp.c @@ -17,6 +17,7 @@ #include #include #include +#include #include #include @@ -435,6 +436,13 @@ static void __cpuinit xen_play_dead(void) /* used only with HOTPLUG_CPU */ 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(); + /* * Balance out the preempt calls - as we are running in cpu_idle * loop which has been called at bootup from cpu_bringup_and_idle. * The cpucpu_bringup_and_idle called cpu_bringup which made a -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/