linux-kernel - [PATCH] cpufreq_sched: set governor

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Date:	Sat, 20 Feb 2016 19:32:46 +0800
From:	Pingbo Wen <pingbo.wen@...aro.org>
To:	eas-dev@...ts.linaro.org
Cc:	mturquette@...libre.com, smuckle@...aro.org,
	linux-kernel@...r.kernel.org, Pingbo Wen <pingbo.wen@...aro.org>
Subject: [PATCH] cpufreq_sched: set governor_data before waking up kschedfreq

Fix null pointer dereference error liked below. This BUG can be easily
re-produced by 'monkey --throttle 50' in android 6.0.

Unable to handle kernel NULL pointer dereference at virtual address 00000010
[KERN Warning] check backtrace:
CPU: 0 PID: 10714 Comm: kschedfreq:0 Tainted:
Call trace:
[<ffffffc00008b8ac>] dump_backtrace+0x0/0x15c
[<ffffffc00008ba18>] show_stack+0x10/0x1c
[<ffffffc000b97bf8>] dump_stack+0x74/0xb8
[<ffffffc00036208c>] debug_locks_off+0x4c/0x7c
[<ffffffc0000a3450>] oops_enter+0xc/0x28
[<ffffffc00008ba50>] die+0x2c/0x1a4
[<ffffffc000b96588>] __do_kernel_fault.part.5+0x70/0x84
[<ffffffc00009c728>] do_page_fault+0x344/0x348
[<ffffffc00009c7e8>] do_translation_fault+0xbc/0xf0
[<ffffffc0000822b0>] do_mem_abort+0x38/0x9c
[<ffffffc000085c50>] el1_da+0x14/0x80
[<ffffffc0000c0168>] kthread+0xd4/0xec

Signed-off-by: Pingbo Wen <pingbo.wen@...aro.org>
---
 kernel/sched/cpufreq_sched.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/cpufreq_sched.c b/kernel/sched/cpufreq_sched.c
index e1d208e..93731ef 100644
--- a/kernel/sched/cpufreq_sched.c
+++ b/kernel/sched/cpufreq_sched.c
@@ -265,6 +265,8 @@ static int cpufreq_sched_policy_init(struct cpufreq_policy *policy)
 	pr_debug("%s: throttle threshold = %u [ns]\n",
 		  __func__, gd->throttle_nsec);
 
+	policy->governor_data = gd;
+
 	if (cpufreq_driver_is_slow()) {
 		cpufreq_driver_slow = true;
 		gd->task = kthread_create(cpufreq_sched_thread, policy,
@@ -281,7 +283,6 @@ static int cpufreq_sched_policy_init(struct cpufreq_policy *policy)
 		init_irq_work(&gd->irq_work, cpufreq_sched_irq_work);
 	}
 
-	policy->governor_data = gd;
 	set_sched_freq();
 
 	return 0;
-- 
1.9.1