1. 19 2月, 2015 2 次提交
  2. 12 2月, 2015 1 次提交
    • M
      cpufreq: speedstep-smi: enable interrupts when waiting · d4d4eda2
      Mikulas Patocka 提交于
      On Dell Latitude C600 laptop with Pentium 3 850MHz processor, the
      speedstep-smi driver sometimes loads and sometimes doesn't load with
      "change to state X failed" message.
      
      The hardware sometimes refuses to change frequency and in this case, we
      need to retry later. I found out that we need to enable interrupts while
      waiting. When we enable interrupts, the hardware blockage that prevents
      frequency transition resolves and the transition is possible. With
      disabled interrupts, the blockage doesn't resolve (no matter how long do
      we wait). The exact reasons for this hardware behavior are unknown.
      
      This patch enables interrupts in the function speedstep_set_state that can
      be called with disabled interrupts. However, this function is called with
      disabled interrupts only from speedstep_get_freqs, so it shouldn't cause
      any problem.
      
      Signed-off-by: Mikulas Patocka <mpatocka@redhat.com
      Cc: All applicable <stable@vger.kernel.org>
      Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
      Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      d4d4eda2
  3. 10 2月, 2015 1 次提交
  4. 07 2月, 2015 1 次提交
  5. 04 2月, 2015 4 次提交
  6. 03 2月, 2015 1 次提交
    • V
      cpufreq: Set cpufreq_cpu_data to NULL before putting kobject · 6ffae8c0
      Viresh Kumar 提交于
      In __cpufreq_remove_dev_finish(), per-cpu 'cpufreq_cpu_data' needs
      to be cleared before calling kobject_put(&policy->kobj) and under
      cpufreq_driver_lock. Otherwise, if someone else calls cpufreq_cpu_get()
      in parallel with it, they can obtain a non-NULL policy from that after
      kobject_put(&policy->kobj) was executed.
      
      Consider this case:
      
      Thread A				Thread B
      cpufreq_cpu_get()
        acquire cpufreq_driver_lock
        read-per-cpu cpufreq_cpu_data
      					kobject_put(&policy->kobj);
        kobject_get(&policy->kobj);
      					...
      					per_cpu(&cpufreq_cpu_data, cpu) = NULL
      
      And this will result in a warning like this one:
      
       ------------[ cut here ]------------
       WARNING: CPU: 0 PID: 4 at include/linux/kref.h:47
       kobject_get+0x41/0x50()
       Modules linked in: acpi_cpufreq(+) nfsd auth_rpcgss nfs_acl
       lockd grace sunrpc xfs libcrc32c sd_mod ixgbe igb mdio ahci hwmon
       ...
       Call Trace:
        [<ffffffff81661b14>] dump_stack+0x46/0x58
        [<ffffffff81072b61>] warn_slowpath_common+0x81/0xa0
        [<ffffffff81072c7a>] warn_slowpath_null+0x1a/0x20
        [<ffffffff812e16d1>] kobject_get+0x41/0x50
        [<ffffffff815262a5>] cpufreq_cpu_get+0x75/0xc0
        [<ffffffff81527c3e>] cpufreq_update_policy+0x2e/0x1f0
        [<ffffffff810b8cb2>] ? up+0x32/0x50
        [<ffffffff81381aa9>] ? acpi_ns_get_node+0xcb/0xf2
        [<ffffffff81381efd>] ? acpi_evaluate_object+0x22c/0x252
        [<ffffffff813824f6>] ? acpi_get_handle+0x95/0xc0
        [<ffffffff81360967>] ? acpi_has_method+0x25/0x40
        [<ffffffff81391e08>] acpi_processor_ppc_has_changed+0x77/0x82
        [<ffffffff81089566>] ? move_linked_works+0x66/0x90
        [<ffffffff8138e8ed>] acpi_processor_notify+0x58/0xe7
        [<ffffffff8137410c>] acpi_ev_notify_dispatch+0x44/0x5c
        [<ffffffff8135f293>] acpi_os_execute_deferred+0x15/0x22
        [<ffffffff8108c910>] process_one_work+0x160/0x410
        [<ffffffff8108d05b>] worker_thread+0x11b/0x520
        [<ffffffff8108cf40>] ? rescuer_thread+0x380/0x380
        [<ffffffff81092421>] kthread+0xe1/0x100
        [<ffffffff81092340>] ? kthread_create_on_node+0x1b0/0x1b0
        [<ffffffff81669ebc>] ret_from_fork+0x7c/0xb0
        [<ffffffff81092340>] ? kthread_create_on_node+0x1b0/0x1b0
       ---[ end trace 89e66eb9795efdf7 ]---
      
      The actual code flow is as follows:
      
       Thread A: Workqueue: kacpi_notify
      
       acpi_processor_notify()
         acpi_processor_ppc_has_changed()
               cpufreq_update_policy()
                 cpufreq_cpu_get()
                   kobject_get()
      
       Thread B: xenbus_thread()
      
       xenbus_thread()
         msg->u.watch.handle->callback()
           handle_vcpu_hotplug_event()
             vcpu_hotplug()
               cpu_down()
                 __cpu_notify(CPU_POST_DEAD..)
                   cpufreq_cpu_callback()
                     __cpufreq_remove_dev_finish()
                       cpufreq_policy_put_kobj()
                         kobject_put()
      
      cpufreq_cpu_get() gets the policy from per-cpu variable cpufreq_cpu_data
      under cpufreq_driver_lock, and once it gets a valid policy it expects it
      to not be freed until cpufreq_cpu_put() is called.
      
      But the race happens when another thread puts the kobject first and updates
      cpufreq_cpu_data before or later. And so the first thread gets a valid policy
      structure and before it does kobject_get() on it, the second one has already
      done kobject_put().
      
      Fix this by setting cpufreq_cpu_data to NULL before putting the kobject and that
      too under locks.
      Reported-by: NEthan Zhao <ethan.zhao@oracle.com>
      Reported-by: NSantosh Shilimkar <santosh.shilimkar@oracle.com>
      Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
      Cc: 3.12+ <stable@vger.kernel.org> # 3.12+
      Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      6ffae8c0
  7. 30 1月, 2015 5 次提交
  8. 24 1月, 2015 25 次提交