@@ -492,18 +492,21 @@ void arch_timer_enable_workaround(const struct arch_timer_erratum_workaround *wa
if (local) {
__this_cpu_write(timer_unstable_counter_workaround, wa);
+
+ /*
+ * Use the locked version, as we're called from the CPU
+ * hotplug framework. Otherwise, we end-up in
+ * deadlock-land.
+ */
+ static_branch_enable_cpuslocked(&arch_timer_read_ool_enabled);
} else {
for_each_possible_cpu(i)
per_cpu(timer_unstable_counter_workaround, i) = wa;
+ /* A global workaround is not on the CPU hotplug path. */
+ static_branch_enable(&arch_timer_read_ool_enabled);
}
/*
- * Use the locked version, as we're called from the CPU
- * hotplug framework. Otherwise, we end-up in deadlock-land.
- */
- static_branch_enable_cpuslocked(&arch_timer_read_ool_enabled);
-
- /*
* Don't use the vdso fastpath if errata require using the
* out-of-line counter accessor. We may change our mind pretty
* late in the game (with a per-CPU erratum, for example), so
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"). Since it is applying a global workaround to all CPUs here, it did not hold any CPU locks in this path. arch_timer_acpi_init arch_timer_check_ool_workaround(ate_match_acpi_oem_info, table) arch_timer_enable_workaround(wa, local = false) for_each_possible_cpu() per_cpu() When hot-add a CPU, it will go with a slightly different route. arch_timer_starting_cpu __arch_timer_setup arch_timer_check_ool_workaround(ate_match_local_cap_id, NULL) arch_timer_enable_workaround(wa, local = true) __this_cpu_write() Hence, deal with them differently. Fixes: 450f9689f294 (clocksource/arm_arch_timer: Use static_branch_enable_cpuslocked()) Signed-off-by: Qian Cai <cai@gmx.us> --- Changes since v1: * Fixed the root cause instead of a workaround. drivers/clocksource/arm_arch_timer.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)