[PATCH] cpufreq: remove race while accessing cur_policy

* [PATCH] cpufreq: remove race while accessing cur_policy
@ 2014-05-19  4:54 Bibek Basu
  2014-05-19  6:46 ` Viresh Kumar
  0 siblings, 1 reply; 2+ messages in thread
From: Bibek Basu @ 2014-05-19  4:54 UTC (permalink / raw)
  To: rjw, viresh.kumar; +Cc: cpufreq, linux-pm, Bibek Basu

While accessing cur_policy during executing events
CPUFREQ_GOV_START, CPUFREQ_GOV_STOP, CPUFREQ_GOV_LIMITS,
same mutex lock is not taken, dbs_data->mutex, which leads
to race and data corruption while running continious suspend
resume test. This is seen with ondemand governor with suspend
resume test using rtcwake.

[ 367.405875] Unable to handle kernel NULL pointer dereference at virtual address 00000028
[ 367.427534] pgd = ed610000
[ 367.427545] [00000028] *pgd=adf11831, *pte=00000000, *ppte=00000000
[ 367.427555] Internal error: Oops: 17 [#1] PREEMPT SMP ARM
[ 367.427564] Modules linked in: nvhost_vi
[ 367.427573] CPU: 1 PID: 3243 Comm: rtcwake Not tainted 3.10.24-gf5cf9e5 #1
[ 367.427578] task: ee708040 ti: ed61c000 task.ti: ed61c000
[ 367.427589] PC is at cpufreq_governor_dbs+0x400/0x634
[ 367.427594] LR is at cpufreq_governor_dbs+0x3f8/0x634
[ 367.427600] pc : [<c05652b8>] lr : [<c05652b0>] psr: 600f0013
[ 367.427600] sp : ed61dcb0 ip : 000493e0 fp : c1cc14f0
[ 367.427604] r10: 00000000 r9 : 00000000 r8 : 00000000
[ 367.427608] r7 : eb725280 r6 : c1cc1560 r5 : eb575200 r4 : ebad7740
[ 367.427612] r3 : ee708040 r2 : ed61dca8 r1 : 001ebd24 r0 : 00000000
[ 367.427618] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
[ 367.427622] Control: 10c5387d Table: ad61006a DAC: 00000015
[ 367.429201] [<c05652b8>] (cpufreq_governor_dbs+0x400/0x634) from [<c055f700>] (__cpufreq_governor+0x98/0x1b4)
[ 367.429216] [<c055f700>] (__cpufreq_governor+0x98/0x1b4) from [<c0560770>] (__cpufreq_set_policy+0x250/0x320)
[ 367.429226] [<c0560770>] (__cpufreq_set_policy+0x250/0x320) from [<c0561dcc>] (cpufreq_update_policy+0xcc/0x168)
[ 367.429235] [<c0561dcc>] (cpufreq_update_policy+0xcc/0x168) from [<c0561ed0>] (cpu_freq_notify+0x68/0xdc)
[ 367.429253] [<c0561ed0>] (cpu_freq_notify+0x68/0xdc) from [<c008eff8>] (notifier_call_chain+0x4c/0x8c)
[ 367.429270] [<c008eff8>] (notifier_call_chain+0x4c/0x8c) from [<c008f3d4>] (__blocking_notifier_call_chain+0x50/0x68)
[ 367.429283] [<c008f3d4>] (__blocking_notifier_call_chain+0x50/0x68) from [<c008f40c>] (blocking_notifier_call_chain+0x20/0x28)
[ 367.429301] [<c008f40c>] (blocking_notifier_call_chain+0x20/0x28) from [<c00aac6c>] (pm_qos_update_bounded_target+0xd8/0x310)
[ 367.429314] [<c00aac6c>] (pm_qos_update_bounded_target+0xd8/0x310) from [<c00ab3b0>] (__pm_qos_update_request+0x64/0x70)
[ 367.429328] [<c00ab3b0>] (__pm_qos_update_request+0x64/0x70) from [<c004b4b8>] (tegra_pm_notify+0x114/0x134)
[ 367.429342] [<c004b4b8>] (tegra_pm_notify+0x114/0x134) from [<c008eff8>] (notifier_call_chain+0x4c/0x8c)
[ 367.429355] [<c008eff8>] (notifier_call_chain+0x4c/0x8c) from [<c008f3d4>] (__blocking_notifier_call_chain+0x50/0x68)
[ 367.429366] [<c008f3d4>] (__blocking_notifier_call_chain+0x50/0x68) from [<c008f40c>] (blocking_notifier_call_chain+0x20/0x28)
[ 367.429376] [<c008f40c>] (blocking_notifier_call_chain+0x20/0x28) from [<c00ac228>] (pm_notifier_call_chain+0x1c/0x34)
[ 367.429389] [<c00ac228>] (pm_notifier_call_chain+0x1c/0x34) from [<c00ad38c>] (enter_state+0xec/0x128)
[ 367.429399] [<c00ad38c>] (enter_state+0xec/0x128) from [<c00ad400>] (pm_suspend+0x38/0xa4)
[ 367.429407] [<c00ad400>] (pm_suspend+0x38/0xa4) from [<c00ac114>] (state_store+0x70/0xc0)
[ 367.429423] [<c00ac114>] (state_store+0x70/0xc0) from [<c027b1e8>] (kobj_attr_store+0x14/0x20)
[ 367.429443] [<c027b1e8>] (kobj_attr_store+0x14/0x20) from [<c019cd9c>] (sysfs_write_file+0x104/0x184)
[ 367.429460] [<c019cd9c>] (sysfs_write_file+0x104/0x184) from [<c0143038>] (vfs_write+0xd0/0x19c)
[ 367.429472] [<c0143038>] (vfs_write+0xd0/0x19c) from [<c0143414>] (SyS_write+0x4c/0x78)
[ 367.429485] [<c0143414>] (SyS_write+0x4c/0x78) from [<c000f080>] (ret_fast_syscall+0x0/0x30)
[ 367.429495] Code: e1a00006 eb084346 e59b0020 e5951024 (e5903028)
[ 367.429533] ---[ end trace 0488523c8f6b0f9d ]---

Signed-off-by: Bibek Basu <bbasu@nvidia.com>
---
 drivers/cpufreq/cpufreq_governor.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
index ba43991..e1c6433 100644
--- a/drivers/cpufreq/cpufreq_governor.c
+++ b/drivers/cpufreq/cpufreq_governor.c
@@ -366,6 +366,11 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 		break;
 
 	case CPUFREQ_GOV_LIMITS:
+		mutex_lock(&dbs_data->mutex);
+		if (!cpu_cdbs->cur_policy) {
+			mutex_unlock(&dbs_data->mutex);
+			break;
+		}
 		mutex_lock(&cpu_cdbs->timer_mutex);
 		if (policy->max < cpu_cdbs->cur_policy->cur)
 			__cpufreq_driver_target(cpu_cdbs->cur_policy,
@@ -375,6 +380,7 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 					policy->min, CPUFREQ_RELATION_L);
 		dbs_check_cpu(dbs_data, cpu);
 		mutex_unlock(&cpu_cdbs->timer_mutex);
+		mutex_unlock(&dbs_data->mutex);
 		break;
 	}
 	return 0;
-- 
1.8.1.5


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