[PATCH] cpufreq: powernv: Fix the hardlockup by synchronus smp_call in timer interrupt

[Shilpasri G Bhat]

gpstate_timer_handler() uses synchronous smp_call to set the pstate
on the requested core. This causes the below hard lockup:

[c000003fe566b320] [c0000000001d5340] smp_call_function_single+0x110/0x180 (unreliable)
[c000003fe566b390] [c0000000001d55e0] smp_call_function_any+0x180/0x250
[c000003fe566b3f0] [c000000000acd3e8] gpstate_timer_handler+0x1e8/0x580
[c000003fe566b4a0] [c0000000001b46b0] call_timer_fn+0x50/0x1c0
[c000003fe566b520] [c0000000001b4958] expire_timers+0x138/0x1f0
[c000003fe566b590] [c0000000001b4bf8] run_timer_softirq+0x1e8/0x270
[c000003fe566b630] [c000000000d0d6c8] __do_softirq+0x158/0x3e4
[c000003fe566b710] [c000000000114be8] irq_exit+0xe8/0x120
[c000003fe566b730] [c000000000024d0c] timer_interrupt+0x9c/0xe0
[c000003fe566b760] [c000000000009014] decrementer_common+0x114/0x120
--- interrupt: 901 at doorbell_global_ipi+0x34/0x50
LR = arch_send_call_function_ipi_mask+0x120/0x130
[c000003fe566ba50] [c00000000004876c] arch_send_call_function_ipi_mask+0x4c/0x130 (unreliable)
[c000003fe566ba90] [c0000000001d59f0] smp_call_function_many+0x340/0x450
[c000003fe566bb00] [c000000000075f18] pmdp_invalidate+0x98/0xe0
[c000003fe566bb30] [c0000000003a1120] change_huge_pmd+0xe0/0x270
[c000003fe566bba0] [c000000000349278] change_protection_range+0xb88/0xe40
[c000003fe566bcf0] [c0000000003496c0] mprotect_fixup+0x140/0x340
[c000003fe566bdb0] [c000000000349a74] SyS_mprotect+0x1b4/0x350
[c000003fe566be30] [c00000000000b184] system_call+0x58/0x6c

Fix this by using the asynchronus smp_call in the timer interrupt handler.
We don't have to wait in this handler until the pstates are changed on
the core. This change will not have any impact on the global pstate
ramp-down algorithm.

Reported-by: Nicholas Piggin <npiggin at gmail.com>
Reported-by: Pridhiviraj Paidipeddi <ppaidipe at linux.vnet.ibm.com>
Signed-off-by: Shilpasri G Bhat <shilpa.bhat at linux.vnet.ibm.com>
---
 drivers/cpufreq/powernv-cpufreq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index 0591874..7e0c752 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -721,7 +721,7 @@ void gpstate_timer_handler(struct timer_list *t)
 	spin_unlock(&gpstates->gpstate_lock);
 
 	/* Timer may get migrated to a different cpu on cpu hot unplug */
-	smp_call_function_any(policy->cpus, set_pstate, &freq_data, 1);
+	smp_call_function_any(policy->cpus, set_pstate, &freq_data, 0);
 }
 
 /*
-- 
1.8.3.1