On Mon, 5 Apr 2021 19:42:03 -0400
Waiman Long <long...@redhat.com> wrote:
> +/*
> + * All the print_cpu() callers from sched_debug_show() will be allowed
> + * to contend for sched_debug_lock and use group_path[] as their SEQ_printf()
> + * calls will be much faster. However only one print_cpu() caller from
> + * sysrq_sched_debug_show() which outputs to the console will be allowed
> + * to use group_path[]. Another parallel console writer will have to use
> + * a shorter stack buffer instead. Since the console output will be garbled
> + * anyway, truncation of some cgroup paths shouldn't be a big issue.
> + */
> +#define SEQ_printf_task_group_path(m, tg, fmt...) \
> +{ \
> + unsigned long flags; \
> + int token = m ? TOKEN_NA \
> + : xchg_acquire(&console_token, TOKEN_NONE); \
> + \
> + if (token == TOKEN_NONE) { \
> + char buf[128]; \
> + task_group_path(tg, buf, sizeof(buf)); \
> + SEQ_printf(m, fmt, buf); \
> + } else { \
> + spin_lock_irqsave(&sched_debug_lock, flags); \
> + task_group_path(tg, group_path, sizeof(group_path)); \
> + SEQ_printf(m, fmt, group_path); \
> + spin_unlock_irqrestore(&sched_debug_lock, flags); \
> + if (token == TOKEN_ACQUIRED) \
> + smp_store_release(&console_token, token); \
> + } \
> }
> #endif
And you said my suggestion was complex!
I'll let others review this.
-- Steve
