Call __raw_get_cpu_var() instead of __get_cpu_var()

pfair_activate_plugin() is called in atomic. Calls to __get_cpu_var()
are unsafe in atomic under PreemptRT (call to smp_processor_id()).

Fix this BUG condition (triggered only with debugging kernel features
enabled):

[  156.719784] BUG: using smp_processor_id() in preemptible [00000000] code: setsched/3084
[  156.719791] caller is pfair_activate_plugin+0x1d/0xd0
[  156.719795] Pid: 3084, comm: setsched Not tainted 2.6.33.5-rt22-litmus2010 #390
[  156.719806] Call Trace:
[  156.719812]  [<ffffffff8124bccd>] debug_smp_processor_id+0xed/0xf0
[  156.719815]  [<ffffffff8123b3fd>] pfair_activate_plugin+0x1d/0xd0
[  156.719819]  [<ffffffff81233382>] switch_sched_plugin+0x142/0x1b0
[  156.719822]  [<ffffffff81233a5c>] proc_write_curr+0x6c/0xe0
[  156.719827]  [<ffffffff81580402>] ? _raw_spin_unlock_irqrestore+0x42/0x80
[  156.719831]  [<ffffffff8157eec5>] ? rt_spin_lock_slowunlock+0x55/0x90
[  156.719836]  [<ffffffff81109781>] proc_file_write+0x71/0xb0
[  156.719839]  [<ffffffff81109710>] ? proc_file_write+0x0/0xb0
[  156.719842]  [<ffffffff81103b5d>] proc_reg_write+0x7d/0xc0
[  156.719847]  [<ffffffff810b780a>] vfs_write+0xca/0x160
[  156.719850]  [<ffffffff810b7df3>] sys_write+0x53/0x90
[  156.719855]  [<ffffffff8100246b>] system_call_fastpath+0x16/0x1b
[  156.719905] Switching to LITMUS^RT plugin PFAIR.

1 files changed, 1 insertions, 1 deletions

diff --git a/litmus/sched_pfair.c b/litmus/sched_pfair.c
index ea77d3295290..7d3544b0bdf0 100644
--- a/litmus/sched_pfair.c
+++ b/litmus/sched_pfair.c
@@ -821,7 +821,7 @@ static long pfair_activate_plugin(void)
         int cpu;
         struct pfair_state* state;
 
-        state = &__get_cpu_var(pfair_state);
+        state = &__raw_get_cpu_var(pfair_state);
         pfair_time = current_quantum(state);
 
         TRACE("Activating PFAIR at q=%lu\n", pfair_time);