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

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[ Upstream commit 4e04615679 ]

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
Stable-dep-of: 60f92acb60a9 ("fs/proc: do_task_stat: move thread_group_cputime_adjusted() outside of lock_task_sighand()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Kees Cook
2021-09-29 15:02:15 -07:00
committed by Sasha Levin
parent 3c1b2776ef
commit 9b3834276b
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);