Nowadays ->siglock is overloaded, it would be really nice to change
do_task_stat() to walk through the list of threads lockless. And note
that we are doing while_each_thread() twice!
while_each_thread() is rcu-safe, but thread_group_times() also needs
->siglock to serialize the modifications of signal_struct->prev_Xtime
members.
(however, please note that currently do_task_stat() can race with
wait_task_zombie() which calls thread_group_times() without siglock).
This patch changes the code back to use thread_group_cputime(), as we
did before 0cf55e1e "sched, cputime: Introduce thread_group_times()".
Of course, this makes the output from /proc/pid/stat less accurate, but
otoh this allows us to make do_task_stat() (apart from ->tty bits).
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
fs/proc/array.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
--- 34-rc1/fs/proc/array.c~PROC_5_DTS_TGTS_IS_PITA 2010-03-24 20:47:19.000000000 +0100
+++ 34-rc1/fs/proc/array.c 2010-03-24 20:47:51.000000000 +0100
@@ -403,6 +403,7 @@ static int do_task_stat(struct seq_file
if (lock_task_sighand(task, &flags)) {
struct signal_struct *sig = task->signal;
+ struct task_cputime cputime;
if (sig->tty) {
struct pid *pgrp = tty_get_pgrp(sig->tty);
@@ -433,8 +434,11 @@ static int do_task_stat(struct seq_file
min_flt += sig->min_flt;
maj_flt += sig->maj_flt;
- thread_group_times(task, &utime, &stime);
+
gtime = cputime_add(gtime, sig->gtime);
+ thread_group_cputime(task, &cputime);
+ utime = cputime.utime;
+ stime = cputime.stime;
}
sid = task_session_nr_ns(task, ns);
--
