Commit 4e046156 authored by Kees Cook's avatar Kees Cook Committed by Peter Zijlstra
Browse files

proc: Use task_is_running() for wchan in /proc/$pid/stat 



The implementations of get_wchan() can be expensive. The only information
imparted here is whether or not a process is currently blocked in the
scheduler (and even this doesn't need to be exact). Avoid doing the
heavy lifting of stack walking and just report that information by using
task_is_running().

Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211008111626.211281780@infradead.org
parent cf2a85ef

fs/proc/array.c

+2 −5
Original line number Diff line number Diff line
@@ -541,7 +541,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns, 
	}



	if (permitted && (!whole || num_threads < 2))

		wchan = get_wchan(task);

		wchan = !task_is_running(task);

	if (!whole) {

		min_flt = task->min_flt;

		maj_flt = task->maj_flt;
@@ -606,10 +606,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns, 
	 *

	 * This works with older implementations of procps as well.

	 */

	if (wchan)

		seq_puts(m, " 1");

	else

		seq_puts(m, " 0");

	seq_put_decimal_ull(m, " ", wchan);



	seq_put_decimal_ull(m, " ", 0);

	seq_put_decimal_ull(m, " ", 0);