[PATCH v4] PM / devfreq: Synchronize device_monitor_[start/stop]
From: Mukesh Ojha
Date: Fri Nov 24 2023 - 16:12:48 EST
There is a chance if a frequent switch of the governor
done in a loop result in timer list corruption where
timer cancel being done from two place one from
cancel_delayed_work_sync() and followed by expire_timers()
can be seen from the traces[1].
while true
do
echo "simple_ondemand" > /sys/class/devfreq/1d84000.ufshc/governor
echo "performance" > /sys/class/devfreq/1d84000.ufshc/governor
done
It looks to be issue with devfreq driver where
device_monitor_[start/stop] need to synchronized so that
delayed work should get corrupted while it is either
being queued or running or being cancelled.
Let's use polling flag and devfreq lock to synchronize the
queueing the timer instance twice and work data being
corrupted.
[1]
...
..
<idle>-0 [003] 9436.209662: timer_cancel timer=0xffffff80444f0428
<idle>-0 [003] 9436.209664: timer_expire_entry timer=0xffffff80444f0428 now=0x10022da1c function=__typeid__ZTSFvP10timer_listE_global_addr baseclk=0x10022da1c
<idle>-0 [003] 9436.209718: timer_expire_exit timer=0xffffff80444f0428
kworker/u16:6-14217 [003] 9436.209863: timer_start timer=0xffffff80444f0428 function=__typeid__ZTSFvP10timer_listE_global_addr expires=0x10022da2b now=0x10022da1c flags=182452227
vendor.xxxyyy.ha-1593 [004] 9436.209888: timer_cancel timer=0xffffff80444f0428
vendor.xxxyyy.ha-1593 [004] 9436.216390: timer_init timer=0xffffff80444f0428
vendor.xxxyyy.ha-1593 [004] 9436.216392: timer_start timer=0xffffff80444f0428 function=__typeid__ZTSFvP10timer_listE_global_addr expires=0x10022da2c now=0x10022da1d flags=186646532
vendor.xxxyyy.ha-1593 [005] 9436.220992: timer_cancel timer=0xffffff80444f0428
xxxyyyTraceManag-7795 [004] 9436.261641: timer_cancel timer=0xffffff80444f0428
[2]
9436.261653][ C4] Unable to handle kernel paging request at virtual address dead00000000012a
[ 9436.261664][ C4] Mem abort info:
[ 9436.261666][ C4] ESR = 0x96000044
[ 9436.261669][ C4] EC = 0x25: DABT (current EL), IL = 32 bits
[ 9436.261671][ C4] SET = 0, FnV = 0
[ 9436.261673][ C4] EA = 0, S1PTW = 0
[ 9436.261675][ C4] Data abort info:
[ 9436.261677][ C4] ISV = 0, ISS = 0x00000044
[ 9436.261680][ C4] CM = 0, WnR = 1
[ 9436.261682][ C4] [dead00000000012a] address between user and kernel address ranges
[ 9436.261685][ C4] Internal error: Oops: 96000044 [#1] PREEMPT SMP
[ 9436.261701][ C4] Skip md ftrace buffer dump for: 0x3a982d0
...
[ 9436.262138][ C4] CPU: 4 PID: 7795 Comm: TraceManag Tainted: G S W O 5.10.149-android12-9-o-g17f915d29d0c #1
[ 9436.262141][ C4] Hardware name: Qualcomm Technologies, Inc. (DT)
[ 9436.262144][ C4] pstate: 22400085 (nzCv daIf +PAN -UAO +TCO BTYPE=--)
[ 9436.262161][ C4] pc : expire_timers+0x9c/0x438
[ 9436.262164][ C4] lr : expire_timers+0x2a4/0x438
[ 9436.262168][ C4] sp : ffffffc010023dd0
[ 9436.262171][ C4] x29: ffffffc010023df0 x28: ffffffd0636fdc18
[ 9436.262178][ C4] x27: ffffffd063569dd0 x26: ffffffd063536008
[ 9436.262182][ C4] x25: 0000000000000001 x24: ffffff88f7c69280
[ 9436.262185][ C4] x23: 00000000000000e0 x22: dead000000000122
[ 9436.262188][ C4] x21: 000000010022da29 x20: ffffff8af72b4e80
[ 9436.262191][ C4] x19: ffffffc010023e50 x18: ffffffc010025038
[ 9436.262195][ C4] x17: 0000000000000240 x16: 0000000000000201
[ 9436.262199][ C4] x15: ffffffffffffffff x14: ffffff889f3c3100
[ 9436.262203][ C4] x13: ffffff889f3c3100 x12: 00000000049f56b8
[ 9436.262207][ C4] x11: 00000000049f56b8 x10: 00000000ffffffff
[ 9436.262212][ C4] x9 : ffffffc010023e50 x8 : dead000000000122
[ 9436.262216][ C4] x7 : ffffffffffffffff x6 : ffffffc0100239d8
[ 9436.262220][ C4] x5 : 0000000000000000 x4 : 0000000000000101
[ 9436.262223][ C4] x3 : 0000000000000080 x2 : ffffff889edc155c
[ 9436.262227][ C4] x1 : ffffff8001005200 x0 : ffffff80444f0428
[ 9436.262232][ C4] Call trace:
[ 9436.262236][ C4] expire_timers+0x9c/0x438
[ 9436.262240][ C4] __run_timers+0x1f0/0x330
[ 9436.262245][ C4] run_timer_softirq+0x28/0x58
[ 9436.262255][ C4] efi_header_end+0x168/0x5ec
[ 9436.262265][ C4] __irq_exit_rcu+0x108/0x124
[ 9436.262274][ C4] __handle_domain_irq+0x118/0x1e4
[ 9436.262282][ C4] gic_handle_irq.30369+0x6c/0x2bc
[ 9436.262286][ C4] el0_irq_naked+0x60/0x6c
Reported-by: Joyyoung Huang <huangzaiyang@xxxxxxxx>
Signed-off-by: Mukesh Ojha <quic_mojha@xxxxxxxxxxx>
---
Huang,
Would be looking for your tested-by..
-Mukesh
Changes in v4: https://lore.kernel.org/lkml/1700238027-20518-1-git-send-email-quic_mojha@xxxxxxxxxxx/
- Mistakenly put cancel work under devfreq lock which could result in deadlock
reported by [Joyyoung Huang]
https://lore.kernel.org/lkml/KL1PR02MB8141D1A307457AF69EBB6AFBA3B8A@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Changes in v3: https://lore.kernel.org/lkml/1700235522-31105-1-git-send-email-quic_mojha@xxxxxxxxxxx/
- Remove the unexpected 'twice' from the subject.
Changes in v2: https://lore.kernel.org/lkml/1699957648-31299-1-git-send-email-quic_mojha@xxxxxxxxxxx/
- Changed subject.
- Added lock to avoid work data corruption due to
parallel calls to devfreq_monitor_start while work
is queued in flight.
- Added lock to cover the same as above case while the
work is being cancelled.
- Added Reported-by for similar issue reported at
https://lore.kernel.org/lkml/SEYPR02MB565398175FA093AC3E63EE7BA3B0A@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
drivers/devfreq/devfreq.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index b3a68d5833bd..cb1c24721a37 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -461,10 +461,14 @@ static void devfreq_monitor(struct work_struct *work)
if (err)
dev_err(&devfreq->dev, "dvfs failed with (%d) error\n", err);
+ if (devfreq->stop_polling)
+ goto out;
+
queue_delayed_work(devfreq_wq, &devfreq->work,
msecs_to_jiffies(devfreq->profile->polling_ms));
- mutex_unlock(&devfreq->lock);
+out:
+ mutex_unlock(&devfreq->lock);
trace_devfreq_monitor(devfreq);
}
@@ -483,6 +487,10 @@ void devfreq_monitor_start(struct devfreq *devfreq)
if (IS_SUPPORTED_FLAG(devfreq->governor->flags, IRQ_DRIVEN))
return;
+ mutex_lock(&devfreq->lock);
+ if (delayed_work_pending(&devfreq->work))
+ goto out;
+
switch (devfreq->profile->timer) {
case DEVFREQ_TIMER_DEFERRABLE:
INIT_DEFERRABLE_WORK(&devfreq->work, devfreq_monitor);
@@ -491,12 +499,16 @@ void devfreq_monitor_start(struct devfreq *devfreq)
INIT_DELAYED_WORK(&devfreq->work, devfreq_monitor);
break;
default:
- return;
+ goto out;
}
if (devfreq->profile->polling_ms)
queue_delayed_work(devfreq_wq, &devfreq->work,
msecs_to_jiffies(devfreq->profile->polling_ms));
+
+out:
+ devfreq->stop_polling = false;
+ mutex_unlock(&devfreq->lock);
}
EXPORT_SYMBOL(devfreq_monitor_start);
@@ -513,6 +525,14 @@ void devfreq_monitor_stop(struct devfreq *devfreq)
if (IS_SUPPORTED_FLAG(devfreq->governor->flags, IRQ_DRIVEN))
return;
+ mutex_lock(&devfreq->lock);
+ if (devfreq->stop_polling) {
+ mutex_unlock(&devfreq->lock);
+ return;
+ }
+
+ devfreq->stop_polling = true;
+ mutex_unlock(&devfreq->lock);
cancel_delayed_work_sync(&devfreq->work);
}
EXPORT_SYMBOL(devfreq_monitor_stop);
--
2.7.4