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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: Kees Cook <keescook@chromium.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211008111626.211281780@infradead.org
This commit is contained in:
Kees Cook 2021-09-29 15:02:15 -07:00 committed by Peter Zijlstra
parent cf2a85efda
commit 4e04615679
1 changed files with 2 additions and 5 deletions
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7
fs/proc/array.c
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@ -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);