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getrusage: move thread_group_cputime_adjusted() outside of lock_task_sighand()

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[ Upstream commit daa694e413 ]

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>
This commit is contained in:
Oleg Nesterov 2024-01-22 16:50:50 +01:00 committed by Sasha Levin
parent c5579e7280
commit 18c7394e46
1 changed files with 21 additions and 17 deletions
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38
kernel/sys.c
View file

@ -1763,17 +1763,19 @@ 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))
@ -1797,9 +1799,6 @@ 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;
@ -1819,19 +1818,24 @@ void getrusage(struct task_struct *p, int who, struct rusage *r)
}
unlock_task_sighand(p, &flags);
out:
if (who == RUSAGE_CHILDREN)
goto out_children;
thread_group_cputime_adjusted(p, &tgutime, &tgstime);
utime += tgutime;
stime += tgstime;
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);
if (who != RUSAGE_CHILDREN) {
struct mm_struct *mm = get_task_mm(p);
if (mm) {
setmax_mm_hiwater_rss(&maxrss, mm);
mmput(mm);
}
}
r->ru_maxrss = maxrss * (PAGE_SIZE / 1024); /* convert pages to KBs */
}
SYSCALL_DEFINE2(getrusage, int, who, struct rusage __user *, ru)