From: Oleg Nesterov oleg@redhat.com
[ Upstream commit daa694e4137571b4ebec330f9a9b4d54aa8b8089 ]
Patch series "getrusage: use sig->stats_lock", v2.
This patch (of 2):
thread_group_cputime() does its own locking, we can safely shift thread_group_cputime_adjusted() which does another for_each_thread loop outside of ->siglock protected section.
This is also preparation for the next patch which changes getrusage() to use stats_lock instead of siglock, thread_group_cputime() takes the same lock. With the current implementation recursive read_seqbegin_or_lock() is fine, thread_group_cputime() can't enter the slow mode if the caller holds stats_lock, yet this looks more safe and better performance-wise.
Link: https://lkml.kernel.org/r/20240122155023.GA26169@redhat.com Link: https://lkml.kernel.org/r/20240122155050.GA26205@redhat.com Signed-off-by: Oleg Nesterov oleg@redhat.com Reported-by: Dylan Hatch dylanbhatch@google.com Tested-by: Dylan Hatch dylanbhatch@google.com Cc: Eric W. Biederman ebiederm@xmission.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sys.c | 34 +++++++++++++++++++--------------- 1 file changed, 19 insertions(+), 15 deletions(-)
diff --git a/kernel/sys.c b/kernel/sys.c index 8a53d858d7375..26c8783bd0757 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1736,17 +1736,19 @@ void getrusage(struct task_struct *p, int who, struct rusage *r) struct task_struct *t; unsigned long flags; u64 tgutime, tgstime, utime, stime; - unsigned long maxrss = 0; + unsigned long maxrss; + struct mm_struct *mm; struct signal_struct *sig = p->signal;
- memset((char *)r, 0, sizeof (*r)); + memset(r, 0, sizeof(*r)); utime = stime = 0; + maxrss = 0;
if (who == RUSAGE_THREAD) { task_cputime_adjusted(current, &utime, &stime); accumulate_thread_rusage(p, r); maxrss = sig->maxrss; - goto out; + goto out_thread; }
if (!lock_task_sighand(p, &flags)) @@ -1770,9 +1772,6 @@ void getrusage(struct task_struct *p, int who, struct rusage *r) fallthrough;
case RUSAGE_SELF: - thread_group_cputime_adjusted(p, &tgutime, &tgstime); - utime += tgutime; - stime += tgstime; r->ru_nvcsw += sig->nvcsw; r->ru_nivcsw += sig->nivcsw; r->ru_minflt += sig->min_flt; @@ -1792,19 +1791,24 @@ void getrusage(struct task_struct *p, int who, struct rusage *r) } unlock_task_sighand(p, &flags);
-out: - r->ru_utime = ns_to_kernel_old_timeval(utime); - r->ru_stime = ns_to_kernel_old_timeval(stime); + if (who == RUSAGE_CHILDREN) + goto out_children;
- if (who != RUSAGE_CHILDREN) { - struct mm_struct *mm = get_task_mm(p); + thread_group_cputime_adjusted(p, &tgutime, &tgstime); + utime += tgutime; + stime += tgstime;
- if (mm) { - setmax_mm_hiwater_rss(&maxrss, mm); - mmput(mm); - } +out_thread: + mm = get_task_mm(p); + if (mm) { + setmax_mm_hiwater_rss(&maxrss, mm); + mmput(mm); } + +out_children: r->ru_maxrss = maxrss * (PAGE_SIZE / 1024); /* convert pages to KBs */ + r->ru_utime = ns_to_kernel_old_timeval(utime); + r->ru_stime = ns_to_kernel_old_timeval(stime); }
SYSCALL_DEFINE2(getrusage, int, who, struct rusage __user *, ru)