cpufreq: interactive: Fix null pointer dereference in interactive gov…

…ernor

For the sync_freq feature currently we check pcpu->policy->cur frequency
for each online cpu.  But for a CPU that isn't using interactive governor
or for an offline CPU, pcpu->policy can be null or an invalid value.
This patch tries to avoid that scenario by using pcpu->target_freq
instead of policy->cur to get the frequency of an online CPU.

Kernel crash without this patch:
[   20.132373] Unable to handle kernel NULL pointer dereference at virtual address 00000028
[   20.132375] pgd = c34f34c0
[   20.132377] pgd = ef6f2440
[   20.132383] [00000028] *pgd=00000000
[   20.132385]
[   20.132388] [00000028] *pgd=2e98f003, *pmd=00000000
[   20.132390] Internal error: Oops: 205 [#1] PREEMPT SMP ARM
[   20.132394] Modules linked in:
[   20.132398] CPU: 0 PID: 1560 Comm: chown Tainted: G        W    3.10.0-perf-gb12057b-00001-ga2c6c16-dirty #7
[   20.132401] task: ef9af300 ti: ee49c000 task.ti: ee49c000
[   20.132411] PC is at cpufreq_interactive_timer+0x10c/0x650
[   20.132415] LR is at cpufreq_interactive_timer+0x128/0x650
<snip>
[   20.133002] [<c07eb204>] (cpufreq_interactive_timer+0x10c/0x650) from [<c02804d8>] (call_timer_fn+0x80/0x198)
[   20.133012] [<c02804d8>] (call_timer_fn+0x80/0x198) from [<c0280acc>] (run_timer_softirq+0x1f8/0x270)
[   20.133019] [<c0280acc>] (run_timer_softirq+0x1f8/0x270) from [<c0279e20>] (__do_softirq+0x12c/0x2d4)
[   20.133025] [<c0279e20>] (__do_softirq+0x12c/0x2d4) from [<c027a2d4>] (irq_exit+0x74/0xc8)
[   20.133034] [<c027a2d4>] (irq_exit+0x74/0xc8) from [<c0206a00>] (handle_IRQ+0x68/0x8c)
[   20.133041] [<c0206a00>] (handle_IRQ+0x68/0x8c) from [<c02004b8>] (gic_handle_irq+0x3c/0x60)
[   20.133051] [<c02004b8>] (gic_handle_irq+0x3c/0x60) from [<c0ac6900>] (__irq_svc+0x40/0x70)
<snip>

Change-Id: Ie834f5d383de4d41e0fe6fbd40c8b0a0c05d82f5
Signed-off-by: Vijay Ganti <[email protected]>
Signed-off-by: franciscofranco <[email protected]>

drivers/cpufreq/cpufreq_interactive.c

@@ -426,7 +426,7 @@ static void cpufreq_interactive_timer(unsigned long data)
 					continue;
 
 				max_load = max(max_load, picpu->prev_load);
-				max_freq = max(max_freq, picpu->policy->cur);
+				max_freq = max(max_freq, picpu->target_freq);
 			}
 
 			if (max_freq > up_threshold_any_cpu_freq &&
@@ -1244,6 +1244,7 @@ static int cpufreq_governor_interactive(struct cpufreq_policy *policy,
 			pcpu = &per_cpu(cpuinfo, j);
 			down_write(&pcpu->enable_sem);
 			pcpu->governor_enabled = 0;
+			pcpu->target_freq = 0;
 			del_timer_sync(&pcpu->cpu_timer);
 			del_timer_sync(&pcpu->cpu_slack_timer);
 			up_write(&pcpu->enable_sem);