Messages in this thread Patch in this message | | | From | Qian Cai <> | Subject | [PATCH] clocksource/arm_arch_timer: fix a lockdep warning | Date | Mon, 3 Dec 2018 14:33:44 -0500 |
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Booting this Huawei TaiShan 2280 arm64 server generated this lockdep warning.
[ 0.000000] lockdep_assert_cpus_held+0x50/0x60 [ 0.000000] static_key_enable_cpuslocked+0x30/0xe8 [ 0.000000] arch_timer_check_ool_workaround+0x128/0x2d0 [ 0.000000] arch_timer_acpi_init+0x274/0x6ac [ 0.000000] acpi_table_parse+0x1ac/0x218 [ 0.000000] __acpi_probe_device_table+0x164/0x1ec [ 0.000000] timer_probe+0x1bc/0x254 [ 0.000000] time_init+0x44/0x98 [ 0.000000] start_kernel+0x4ec/0x7d4
This is due to the commit cb538267ea1e ("jump_label/lockdep: Assert we hold the hotplug lock for _cpuslocked() operations"). Therefore, it will check if it is really in the CPU hotplug path or not, and work around this problem by using cpus_read_trylock(). The chance of not getting the read lock is very small. If that happens, it will report a lockdep warning at most.
Signed-off-by: Qian Cai <cai@gmx.us> --- drivers/clocksource/arm_arch_timer.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c index 9a7d4dc..5c9acbd 100644 --- a/drivers/clocksource/arm_arch_timer.c +++ b/drivers/clocksource/arm_arch_timer.c @@ -497,11 +497,20 @@ void arch_timer_enable_workaround(const struct arch_timer_erratum_workaround *wa per_cpu(timer_unstable_counter_workaround, i) = wa; } +#ifdef CONFIG_HOTPLUG_CPU + i = 0; + /* * Use the locked version, as we're called from the CPU * hotplug framework. Otherwise, we end-up in deadlock-land. */ + i = cpus_read_trylock(); static_branch_enable_cpuslocked(&arch_timer_read_ool_enabled); + if (i) + cpus_read_unlock(); +#else + static_branch_enable(&arch_timer_read_ool_enabled); +#endif /* * Don't use the vdso fastpath if errata require using the -- 1.8.3.1
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