On 4/5/21 8:18 PM, Steven Rostedt wrote:
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.
This patch is actually inspired by your suggestion, though it is
structured differently from your approach. I really want to thank you
for your valuable feedback.
I realized that printing to a sequence file wasn't really a problem,
only printing to console can be problematic. That is why I decided to
allow unlimited use of group_path[] for those users and only one console
writer is allowed to use it. As for calling touch_nmi_watchdog(), I am
still thinking where will be the right place to do it, but it can be
done with a separate patch, if needed.
Cheers,
Longman
