On 1/26/24 15:23, Andrew Jones wrote:
> Remove spinlocks from on_cpu_async() by pulling some of their
> use into a new function and also by narrowing the locking to a
> single on_cpu_info structure by introducing yet another cpumask.
>
> Signed-off-by: Andrew Jones <andrew.jones@xxxxxxxxx>
> Acked-by: Thomas Huth <thuth@xxxxxxxxxx>
Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
Eric
> ---
> lib/arm/asm/smp.h | 4 +++-
> lib/arm/smp.c | 37 ++++++++++++++++++++++++++++---------
> 2 files changed, 31 insertions(+), 10 deletions(-)
>
> diff --git a/lib/arm/asm/smp.h b/lib/arm/asm/smp.h
> index 9f6d839ab568..f0c0f97a19f8 100644
> --- a/lib/arm/asm/smp.h
> +++ b/lib/arm/asm/smp.h
> @@ -27,9 +27,11 @@ extern bool cpu0_calls_idle;
> extern void halt(void);
> extern void do_idle(void);
>
> -extern void smp_boot_secondary(int cpu, secondary_entry_fn entry);
> extern void on_cpu_async(int cpu, void (*func)(void *data), void *data);
> extern void on_cpu(int cpu, void (*func)(void *data), void *data);
> extern void on_cpus(void (*func)(void *data), void *data);
>
> +extern void smp_boot_secondary(int cpu, secondary_entry_fn entry);
> +extern void smp_boot_secondary_nofail(int cpu, secondary_entry_fn entry);
> +
> #endif /* _ASMARM_SMP_H_ */
> diff --git a/lib/arm/smp.c b/lib/arm/smp.c
> index c00fda2efb03..e0872a1a72c2 100644
> --- a/lib/arm/smp.c
> +++ b/lib/arm/smp.c
> @@ -76,12 +76,32 @@ void smp_boot_secondary(int cpu, secondary_entry_fn entry)
> spin_unlock(&lock);
> }
>
> +void smp_boot_secondary_nofail(int cpu, secondary_entry_fn entry)
> +{
> + spin_lock(&lock);
> + if (!cpu_online(cpu))
> + __smp_boot_secondary(cpu, entry);
> + spin_unlock(&lock);
> +}
> +
> struct on_cpu_info {
> void (*func)(void *data);
> void *data;
> cpumask_t waiters;
> };
> static struct on_cpu_info on_cpu_info[NR_CPUS];
> +static cpumask_t on_cpu_info_lock;
> +
> +static bool get_on_cpu_info(int cpu)
> +{
> + return !cpumask_test_and_set_cpu(cpu, &on_cpu_info_lock);
> +}
> +
> +static void put_on_cpu_info(int cpu)
> +{
> + int ret = cpumask_test_and_clear_cpu(cpu, &on_cpu_info_lock);
> + assert(ret);
> +}
>
> static void __deadlock_check(int cpu, const cpumask_t *waiters, bool *found)
> {
> @@ -158,22 +178,21 @@ void on_cpu_async(int cpu, void (*func)(void *data), void *data)
> assert_msg(cpu != 0 || cpu0_calls_idle, "Waiting on CPU0, which is unlikely to idle. "
> "If this is intended set cpu0_calls_idle=1");
>
> - spin_lock(&lock);
> - if (!cpu_online(cpu))
> - __smp_boot_secondary(cpu, do_idle);
> - spin_unlock(&lock);
> + smp_boot_secondary_nofail(cpu, do_idle);
>
> for (;;) {
> cpu_wait(cpu);
> - spin_lock(&lock);
> - if ((volatile void *)on_cpu_info[cpu].func == NULL)
> - break;
> - spin_unlock(&lock);
> + if (get_on_cpu_info(cpu)) {
> + if ((volatile void *)on_cpu_info[cpu].func == NULL)
> + break;
> + put_on_cpu_info(cpu);
> + }
> }
> +
> on_cpu_info[cpu].func = func;
> on_cpu_info[cpu].data = data;
> - spin_unlock(&lock);
> set_cpu_idle(cpu, false);
> + put_on_cpu_info(cpu);
> smp_send_event();
> }
>
