On Mon, Apr 08, 2019 at 04:49:06PM +0100, Marc Zyngier wrote:
> The use of a static key in a hotplug path has proved to be a real
> nightmare, and makes it impossible to have scream-free lockdep
> kernel.
>
> Let's remove the static key altogether, and focus on something saner.
>
> Signed-off-by: Marc Zyngier <marc.zyng...@arm.com>
Acked-by: Mark Rutland <mark.rutl...@arm.com>
Mark.
> ---
> arch/arm64/include/asm/arch_timer.h | 4 ----
> drivers/clocksource/arm_arch_timer.c | 25 +++++++------------------
> 2 files changed, 7 insertions(+), 22 deletions(-)
>
> diff --git a/arch/arm64/include/asm/arch_timer.h
> b/arch/arm64/include/asm/arch_timer.h
> index 4a06d46def7e..5502ea049b63 100644
> --- a/arch/arm64/include/asm/arch_timer.h
> +++ b/arch/arm64/include/asm/arch_timer.h
> @@ -45,13 +45,9 @@
> (__wa && __wa->h) ? __wa->h : arch_timer_##h; \
> })
>
> -extern struct static_key_false arch_timer_read_ool_enabled;
> -#define needs_unstable_timer_counter_workaround() \
> - static_branch_unlikely(&arch_timer_read_ool_enabled)
> #else
> #define has_erratum_handler(h) false
> #define erratum_handler(h) (arch_timer_##h)
> -#define needs_unstable_timer_counter_workaround() false
> #endif
>
> enum arch_timer_erratum_match_type {
> diff --git a/drivers/clocksource/arm_arch_timer.c
> b/drivers/clocksource/arm_arch_timer.c
> index c7f5b66d893c..da487fbfada3 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -372,8 +372,6 @@ static u32 notrace sun50i_a64_read_cntv_tval_el0(void)
> DEFINE_PER_CPU(const struct arch_timer_erratum_workaround *,
> timer_unstable_counter_workaround);
> EXPORT_SYMBOL_GPL(timer_unstable_counter_workaround);
>
> -DEFINE_STATIC_KEY_FALSE(arch_timer_read_ool_enabled);
> -EXPORT_SYMBOL_GPL(arch_timer_read_ool_enabled);
>
> static void erratum_set_next_event_tval_generic(const int access, unsigned
> long evt,
> struct clock_event_device *clk)
> @@ -552,12 +550,6 @@ void arch_timer_enable_workaround(const struct
> arch_timer_erratum_workaround *wa
> per_cpu(timer_unstable_counter_workaround, i) = 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);
> -
> /*
> * Don't use the vdso fastpath if errata require using the
> * out-of-line counter accessor. We may change our mind pretty
> @@ -573,7 +565,7 @@ void arch_timer_enable_workaround(const struct
> arch_timer_erratum_workaround *wa
> static void arch_timer_check_ool_workaround(enum
> arch_timer_erratum_match_type type,
> void *arg)
> {
> - const struct arch_timer_erratum_workaround *wa;
> + const struct arch_timer_erratum_workaround *wa, *__wa;
> ate_match_fn_t match_fn = NULL;
> bool local = false;
>
> @@ -597,16 +589,13 @@ static void arch_timer_check_ool_workaround(enum
> arch_timer_erratum_match_type t
> if (!wa)
> return;
>
> - if (needs_unstable_timer_counter_workaround()) {
> - const struct arch_timer_erratum_workaround *__wa;
> - __wa = __this_cpu_read(timer_unstable_counter_workaround);
> - if (__wa && wa != __wa)
> - pr_warn("Can't enable workaround for %s (clashes with
> %s\n)",
> - wa->desc, __wa->desc);
> + __wa = __this_cpu_read(timer_unstable_counter_workaround);
> + if (__wa && wa != __wa)
> + pr_warn("Can't enable workaround for %s (clashes with %s\n)",
> + wa->desc, __wa->desc);
>
> - if (__wa)
> - return;
> - }
> + if (__wa)
> + return;
>
> arch_timer_enable_workaround(wa, local);
> pr_info("Enabling %s workaround for %s\n",
> --
> 2.20.1
>
