[Xen-changelog] [xen stable-4.8] x86/cpuidle: don't init stats lock more than once

[patchbot@xxxxxxx]

commit f2837b5f11394fc8107f0a06b2cebaa4f8d42d7c
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri May 18 12:11:58 2018 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri May 18 12:11:58 2018 +0200

    x86/cpuidle: don't init stats lock more than once
    
    Osstest flight 122363, having hit an NMI watchdog timeout, shows CPU1 at
    
    Xen call trace:
       [<ffff82d08023d3f4>] _spin_lock+0x30/0x57
       [<ffff82d0802d9346>] update_last_cx_stat+0x29/0x42
       [<ffff82d0802d96f3>] cpu_idle.c#acpi_processor_idle+0x2ff/0x596
       [<ffff82d080276713>] domain.c#idle_loop+0xa8/0xc3
    
    and CPU0 at
    
    Xen call trace:
       [<ffff82d08023d173>] on_selected_cpus+0xb7/0xde
       [<ffff82d0802dbe22>] powernow.c#powernow_cpufreq_target+0x110/0x1cb
       [<ffff82d080257973>] __cpufreq_driver_target+0x43/0xa6
       [<ffff82d080256b0d>] cpufreq_governor_dbs+0x324/0x37a
       [<ffff82d080257bf2>] __cpufreq_set_policy+0xfa/0x19d
       [<ffff82d080256044>] cpufreq_add_cpu+0x3a1/0x5df
       [<ffff82d0802dbab4>] cpufreq_cpu_init+0x17/0x1a
       [<ffff82d0802567a8>] set_px_pminfo+0x2b6/0x2f7
       [<ffff82d08029f1bf>] do_platform_op+0xe75/0x1977
       [<ffff82d0803712c5>] pv_hypercall+0x1f4/0x440
       [<ffff82d0803784a5>] lstar_enter+0x115/0x120
    
    That is, Dom0's ACPI processor driver is in the process of uploading Px
    and Cx data. Looking at the ticket lock state in CPU1's registers, it is
    waiting for ticket 0x0000 to have its turn, while the supposed current
    owner's ticket is 0x0001, which is an invalid state (and neither of the
    other two CPUs holds the lock anyway). Hence I can only conclude that
    cpuidle_init_cpu(1) ran on CPU 0 while some other CPU held the lock (the
    unlock then put the lock in the state that CPU1 is observing).
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 2f64a251fa10dd4d62f84967e3dafa709f5e96ab
    master date: 2018-04-27 14:35:35 +0200
---
 xen/arch/x86/acpi/cpu_idle.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/acpi/cpu_idle.c b/xen/arch/x86/acpi/cpu_idle.c
index 244667993d..655bc47f0e 100644
--- a/xen/arch/x86/acpi/cpu_idle.c
+++ b/xen/arch/x86/acpi/cpu_idle.c
@@ -833,6 +833,9 @@ int cpuidle_init_cpu(unsigned int cpu)
             acpi_power->states[i].idx = i;
 
         acpi_power->cpu = cpu;
+
+        spin_lock_init(&acpi_power->stat_lock);
+
         processor_powers[cpu] = acpi_power;
     }
 
@@ -840,7 +843,6 @@ int cpuidle_init_cpu(unsigned int cpu)
     acpi_power->states[1].type = ACPI_STATE_C1;
     acpi_power->states[1].entry_method = ACPI_CSTATE_EM_HALT;
     acpi_power->safe_state = &acpi_power->states[1];
-    spin_lock_init(&acpi_power->stat_lock);
 
     return 0;
 }
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.8

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