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Commit 33ec341e authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Sasha Levin
Browse files

getrusage: move thread_group_cputime_adjusted() outside of lock_task_sighand() 

[ 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: default avatarOleg Nesterov <oleg@redhat.com>
Reported-by: default avatarDylan Hatch <dylanbhatch@google.com>
Tested-by: default avatarDylan Hatch <dylanbhatch@google.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent e904c9a4

kernel/sys.c

+19 −15
Original line number Diff line number Diff line
@@ -1717,17 +1717,19 @@ 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))
@@ -1750,9 +1752,6 @@ void getrusage(struct task_struct *p, int who, struct rusage *r) 
			break;



	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;
@@ -1772,19 +1771,24 @@ 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;



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)