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Date: Wed, 8 Nov 2023 22:11:01 +0530
From: Mukesh Ojha <quic_mojha@...cinc.com>
To: <myungjoo.ham@...sung.com>, <kyungmin.park@...sung.com>,
<cw00.choi@...sung.com>, <jstultz@...gle.com>,
<tglx@...utronix.de>, <sboyd@...nel.org>, <tj@...nel.org>,
<jiangshanlai@...il.com>
CC: <linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>
Subject: Re: timer list corruption in devfreq
On 11/8/2023 9:39 PM, Mukesh Ojha wrote:
> Hi,
>
> We are facing an issue on 6.1 kernel while using devfreq framework
> and looks like the devfreq_monitor_stop()/devfreq_monitor_start is
> vulnerable if frequent governor change is being done from user space
> in a loop.
>
> echo simple_ondemand > /sys/class/devfreq/1d84000.ufshc/governor
> echo performance > /sys/class/devfreq/1d84000.ufshc/governor
>
> Here, we are using ufs device, but could be any device.
>
> Issue is because same instance of timer is being queued from two
> places one from devfreq_monitor() and one from devfreq_monitor_start() as
> cancel_delayed_work_sync() from devfreq_monitor_stop() was not
> able to delete the delayed work time completely due to which
> devfreq_monitor() work rearmed the same timer.
>
> But there looks to be issue in the timer framework where
> it was initially discussed in [1] and later fixed in [2]
> but not sure being whether is it issue in cancel_delayed_work_sync()
> where del_timer() inside try_to_grab_pending() need to be replaced
> with timer_delete[_sync]() or devfreq_monitor_stop() need to use
> this api's and then delete the work.
I meant, timer_shutdown_sync().
Well, i am not sure as these patches[2] are not available on LTS kernel.
-Mukesh
>
> [1]
> https://lore.kernel.org/all/20220407161745.7d6754b3@gandalf.local.home/
>
> [2]
> https://lore.kernel.org/all/20221123201306.823305113@linutronix.de/
>
> In the below ftraces, last two are back to back two timer cancel
> operations one from devfreq_monitor_stop() and other from expire_timer().
>
> devfreq_monitor_stop
> cancel_delayed_work_sync
> __cancel_work_timer
> try_to_grab_pending
> del_timer()
>
> 00|__hlist_del(inline) == list corruption
> -000|detach_timer(inline)
> -000|expire_timers(inline) ==>
> -000|__run_timers(base = 0xFFFFFF8A70F31240)
> -001|run_timer_softirq()
> -002|__do_softirq()
> -003|____do_softirq()
> -004|call_on_irq_stack(asm)
> -005|do_softirq_own_stack()
> -006|invoke_softirq(inline)
>
> kworker/u16:2-5133 [002] 9436.089773: timer_start timer=0xffffff80444f0428 function=__typeid__ZTSFvP10timer_listE_global_addr expires=0x10022da0d now=0x10022d9fe flags=56623106
> <idle>-0 [002] 9436.149664: timer_cancel timer=0xffffff80444f0428
> <idle>-0 [002] 9436.149666: timer_expire_entry timer=0xffffff80444f0428 now=0x10022da0d function=__typeid__ZTSFvP10timer_listE_global_addr baseclk=0x10022da0d
> <idle>-0 [002] 9436.149705: timer_expire_exit timer=0xffffff80444f0428
> kworker/u16:6-14217 [003] 9436.149776: timer_start timer=0xffffff80444f0428 function=__typeid__ZTSFvP10timer_listE_global_addr expires=0x10022da1c now=0x10022da0d flags=119537667
> vendor.xxxyyy.ha-1593 [006] 9436.182730: timer_init timer=0xffffff80444f0428
> vendor.xxxyyy.ha-1593 [006] 9436.182731: timer_start timer=0xffffff80444f0428 function=__typeid__ZTSFvP10timer_listE_global_addr expires=0x10022da24 now=0x10022da15 flags=153092102
> vendor.xxxyyy.ha-1593 [004] 9436.188128: timer_cancel timer=0xffffff80444f0428
> vendor.xxxyyy.ha-1593 [004] 9436.193456: timer_init timer=0xffffff80444f0428
> vendor.xxxyyy.ha-1593 [004] 9436.193458: timer_start timer=0xffffff80444f0428 function=__typeid__ZTSFvP10timer_listE_global_addr expires=0x10022da26 now=0x10022da17 flags=161480708
> vendor.xxxyyy.ha-1593 [005] 9436.199602: timer_cancel timer=0xffffff80444f0428
> vendor.xxxyyy.ha-1593 [004] 9436.205410: timer_init timer=0xffffff80444f0428
> vendor.xxxyyy.ha-1593 [004] 9436.205412: timer_start timer=0xffffff80444f0428 function=__typeid__ZTSFvP10timer_listE_global_addr expires=0x10022da29 now=0x10022da1a flags=174063620
> <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
>
> <1>[10278.515522] [cpu: 0] Unable to handle kernel paging request at virtual address dead00000000012a
>
> -000|__hlist_del(inline)
> -000|detach_timer(inline)
> -000|expire_timers(inline)
> -000|__run_timers(base = 0xFFFFFF8A70F31240)
> -001|run_timer_softirq()
> -002|__do_softirq()
> -003|____do_softirq()
> -004|call_on_irq_stack(asm)
> -005|do_softirq_own_stack()
> -006|invoke_softirq(inline)
> -006|__irq_exit_rcu()
> -007|irq_exit_rcu()
> -008|__el1_irq(inline)
> -008|el1_interrupt(regs = 0xFFFFFFC0410FB680, handler = 0xFFFFFFE5222100F8)
> -009|el1h_64_irq_handler(regs = ?)
> -010|el1h_64_irq(asm)
> -->|exception
> -011|arch_local_irq_enable(inline)
> -011|raw_spin_rq_unlock_irq(inline)
> -011|finish_lock_switch(inline)
> -011|finish_task_switch(prev = 0xFFFFFF88D30D8000)
> -012|context_switch(inline)
> -012|__schedule(:sched_mode = 1091549328)
> -013|schedule()
> -014|schedule_hrtimeout_range_clock(expires = ?, delta = ?, mode = ?, clock_id = ?)
> -015|schedule_hrtimeout_range(expires = 0x0, delta = 0, mode = 1091549520)
> -016|poll_schedule_timeout(inline)
> -016|do_poll(inline)
> -016|do_sys_poll(:ufds = 0x00000072B4397BD8, :nfds = 2, :end_time = 0x0)
> -017|__do_sys_ppoll(inline)
> -017|__se_sys_ppoll(inline)
> -017|__arm64_sys_ppoll(:regs = 0xFFFFFFC0410FBEB0)
> -018|__invoke_syscall(inline)
> -018|invoke_syscall(:regs = 0xFFFFFFC0410FBEB0, scno = ?, sc_nr = ?, :syscall_table = 0xFFFFFFE5231E0D20)
> -019|el0_svc_common(regs = 0xFFFFFFC0410FBEB0, scno = ?, sc_nr = ?, syscall_table = 0xFFFFFFE5231E0D20)
> -020|do_el0_svc(regs = 0xFFFFFFC0410FBEB0)
> -021|el0_svc(regs = 0xFFFFFFC0410FBEB0)
> -022|el0t_64_sync_handler(regs = ?)
> -023|el0t_64_sync(asm)
> -->|exception
> -024|NUX:0x736F8F15FC(asm)
> ---|end of frame
> expire_timers(inline)
> expires = 4297461926,
> function = 0xFFFFFFE262CD6E18,
> base = 0xFFFFFF8975713240
> baseclk = 4297461926
> fn = 0x0
> timer = 0xFFFFFF8044AA5430 ->
> ( entry = (next = 0xDEAD000000000122, pprev = 0xFFFFFFC008003EA0 -> 0xDEAD000000000122 ->
> next = 0x0,pprev = 0x0)),
> expires = 4297461926,
> function = 0xFFFFFFE262CD6E18, //delayed_work_timer_fn
>
>
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