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authorNiklas Söderlund2020-12-05 03:19:20 +0100
committerDaniel Lezcano2020-12-07 20:10:05 +0100
commit8ae954caf49ac403c177d117fb8e05cbc866aa3c (patch)
tree0c637a4cff034daa9f864e9c356d14327fb8ca47 /lib/ubsan.h
parent8b7770b877d187bfdae1eaf587bd2b792479a31c (diff)
clocksource/drivers/sh_cmt: Fix potential deadlock when calling runtime PM
The ch->lock is used to protect the whole enable() and read() of sh_cmt's implementation of struct clocksource. The enable() implementation calls pm_runtime_get_sync() which may result in the clock source to be read() triggering a cyclic lockdep warning for the ch->lock. The sh_cmt driver implement its own balancing of calls to sh_cmt_{enable,disable}() with flags in sh_cmt_{start,stop}(). It does this to deal with that start and stop are shared between the clock source and clock event providers. While this could be improved on verifying corner cases based on any substantial rework on all devices this driver supports might prove hard. As a first step separate the PM handling for clock event and clock source. Always put/get the device when enabling/disabling the clock source but keep the clock event logic unchanged. This allows the sh_cmt implementation of struct clocksource to call PM without holding the ch->lock and avoiding the deadlock. Triggering and log of the deadlock warning, # echo e60f0000.timer > /sys/devices/system/clocksource/clocksource0/current_clocksource [ 46.948370] ====================================================== [ 46.954730] WARNING: possible circular locking dependency detected [ 46.961094] 5.10.0-rc6-arm64-renesas-00001-g0e5fd7414e8b #36 Not tainted [ 46.967985] ------------------------------------------------------ [ 46.974342] migration/0/11 is trying to acquire lock: [ 46.979543] ffff0000403ed220 (&dev->power.lock){-...}-{2:2}, at: __pm_runtime_resume+0x40/0x74 [ 46.988445] [ 46.988445] but task is already holding lock: [ 46.994441] ffff000040ad0298 (&ch->lock){....}-{2:2}, at: sh_cmt_start+0x28/0x210 [ 47.002173] [ 47.002173] which lock already depends on the new lock. [ 47.002173] [ 47.010573] [ 47.010573] the existing dependency chain (in reverse order) is: [ 47.018262] [ 47.018262] -> #3 (&ch->lock){....}-{2:2}: [ 47.024033] lock_acquire.part.0+0x120/0x330 [ 47.028970] lock_acquire+0x64/0x80 [ 47.033105] _raw_spin_lock_irqsave+0x7c/0xc4 [ 47.038130] sh_cmt_start+0x28/0x210 [ 47.042352] sh_cmt_clocksource_enable+0x28/0x50 [ 47.047644] change_clocksource+0x9c/0x160 [ 47.052402] multi_cpu_stop+0xa4/0x190 [ 47.056799] cpu_stopper_thread+0x90/0x154 [ 47.061557] smpboot_thread_fn+0x244/0x270 [ 47.066310] kthread+0x154/0x160 [ 47.070175] ret_from_fork+0x10/0x20 [ 47.074390] [ 47.074390] -> #2 (tk_core.seq.seqcount){----}-{0:0}: [ 47.081136] lock_acquire.part.0+0x120/0x330 [ 47.086070] lock_acquire+0x64/0x80 [ 47.090203] seqcount_lockdep_reader_access.constprop.0+0x74/0x100 [ 47.097096] ktime_get+0x28/0xa0 [ 47.100960] hrtimer_start_range_ns+0x210/0x2dc [ 47.106164] generic_sched_clock_init+0x70/0x88 [ 47.111364] sched_clock_init+0x40/0x64 [ 47.115853] start_kernel+0x494/0x524 [ 47.120156] [ 47.120156] -> #1 (hrtimer_bases.lock){-.-.}-{2:2}: [ 47.126721] lock_acquire.part.0+0x120/0x330 [ 47.136042] lock_acquire+0x64/0x80 [ 47.144461] _raw_spin_lock_irqsave+0x7c/0xc4 [ 47.153721] hrtimer_start_range_ns+0x68/0x2dc [ 47.163054] rpm_suspend+0x308/0x5dc [ 47.171473] rpm_idle+0xc4/0x2a4 [ 47.179550] pm_runtime_work+0x98/0xc0 [ 47.188209] process_one_work+0x294/0x6f0 [ 47.197142] worker_thread+0x70/0x45c [ 47.205661] kthread+0x154/0x160 [ 47.213673] ret_from_fork+0x10/0x20 [ 47.221957] [ 47.221957] -> #0 (&dev->power.lock){-...}-{2:2}: [ 47.236292] check_noncircular+0x128/0x140 [ 47.244907] __lock_acquire+0x13b0/0x204c [ 47.253332] lock_acquire.part.0+0x120/0x330 [ 47.262033] lock_acquire+0x64/0x80 [ 47.269826] _raw_spin_lock_irqsave+0x7c/0xc4 [ 47.278430] __pm_runtime_resume+0x40/0x74 [ 47.286758] sh_cmt_start+0x84/0x210 [ 47.294537] sh_cmt_clocksource_enable+0x28/0x50 [ 47.303449] change_clocksource+0x9c/0x160 [ 47.311783] multi_cpu_stop+0xa4/0x190 [ 47.319720] cpu_stopper_thread+0x90/0x154 [ 47.328022] smpboot_thread_fn+0x244/0x270 [ 47.336298] kthread+0x154/0x160 [ 47.343708] ret_from_fork+0x10/0x20 [ 47.351445] [ 47.351445] other info that might help us debug this: [ 47.351445] [ 47.370225] Chain exists of: [ 47.370225] &dev->power.lock --> tk_core.seq.seqcount --> &ch->lock [ 47.370225] [ 47.392003] Possible unsafe locking scenario: [ 47.392003] [ 47.405314] CPU0 CPU1 [ 47.413569] ---- ---- [ 47.421768] lock(&ch->lock); [ 47.428425] lock(tk_core.seq.seqcount); [ 47.438701] lock(&ch->lock); [ 47.447930] lock(&dev->power.lock); [ 47.455172] [ 47.455172] *** DEADLOCK *** [ 47.455172] [ 47.471433] 3 locks held by migration/0/11: [ 47.479099] #0: ffff8000113c9278 (timekeeper_lock){-.-.}-{2:2}, at: change_clocksource+0x2c/0x160 [ 47.491834] #1: ffff8000113c8f88 (tk_core.seq.seqcount){----}-{0:0}, at: multi_cpu_stop+0xa4/0x190 [ 47.504727] #2: ffff000040ad0298 (&ch->lock){....}-{2:2}, at: sh_cmt_start+0x28/0x210 [ 47.516541] [ 47.516541] stack backtrace: [ 47.528480] CPU: 0 PID: 11 Comm: migration/0 Not tainted 5.10.0-rc6-arm64-renesas-00001-g0e5fd7414e8b #36 [ 47.542147] Hardware name: Renesas Salvator-X 2nd version board based on r8a77965 (DT) [ 47.554241] Call trace: [ 47.560832] dump_backtrace+0x0/0x190 [ 47.568670] show_stack+0x14/0x30 [ 47.576144] dump_stack+0xe8/0x130 [ 47.583670] print_circular_bug+0x1f0/0x200 [ 47.592015] check_noncircular+0x128/0x140 [ 47.600289] __lock_acquire+0x13b0/0x204c [ 47.608486] lock_acquire.part.0+0x120/0x330 [ 47.616953] lock_acquire+0x64/0x80 [ 47.624582] _raw_spin_lock_irqsave+0x7c/0xc4 [ 47.633114] __pm_runtime_resume+0x40/0x74 [ 47.641371] sh_cmt_start+0x84/0x210 [ 47.649115] sh_cmt_clocksource_enable+0x28/0x50 [ 47.657916] change_clocksource+0x9c/0x160 [ 47.666165] multi_cpu_stop+0xa4/0x190 [ 47.674056] cpu_stopper_thread+0x90/0x154 [ 47.682308] smpboot_thread_fn+0x244/0x270 [ 47.690560] kthread+0x154/0x160 [ 47.697927] ret_from_fork+0x10/0x20 [ 47.708447] clocksource: Switched to clocksource e60f0000.timer Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Link: https://lore.kernel.org/r/20201205021921.1456190-2-niklas.soderlund+renesas@ragnatech.se
Diffstat (limited to 'lib/ubsan.h')
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