From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B9FE328DBE for ; Thu, 18 Jan 2024 15:58:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705593503; cv=none; b=AZepTDmU7Xld7N/dfRVCHCHmDC07wV72zALVffnEdcqJBriMswuaKzNBdsR8EKNRtnUcDSfYeS9G6vv7H1PZLwwYZ/xPmcOGv7kXcTUiIlZ115v01fphIdw7OiILyt+diqesITXaxR8zpTZPGwPQzM21MxJG4yE1PJBJMNvIsRk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705593503; c=relaxed/simple; bh=8CaDs+CjLaW9DHqUml+lCbr0MBeL3UzroduzmKzDvFg=; h=DKIM-Signature:Received:X-MC-Unique:Received:Received:Received: Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To:User-Agent: X-Scanned-By; b=hvbawmG3MRojDmuo+Aar1mQKmySPNAm16e6MVyIm4Oa22A7Gy1hvz4sVyxojb0I5pVD5sOOmt+vaa5naRsXiKR7bSKJ4yC93DVqWxamTOUXRwEMnw8GDmmaiMb5r5/6pPvlgF5h20xa1ZArAgO5wE8KHHXQ+oKMLXZfBImC6Efw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=aW9U3Cf4; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="aW9U3Cf4" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1705593500; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=AJlRlMSn9Tux/y1MTmqum9WOCp9JOJB/R0qG6qSOtrU=; b=aW9U3Cf4Gz9RZ0t/mwfudRKSoQIgAr9Rb4saq6IPTAp7ES8jIh7ChIu/eJy5X6xnjWgdLc CAk5CN8JcfnB+hwwg84N9/5gT+g/kpzY24ZZVjbMyNcYmgPaAZomTb8fhAifvsKvwaOyfu X+OlWT3gfy+nZKsSLU8C8cPrOrpoLw4= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-648-1oNEHh_KNIiebxOVhiJYUg-1; Thu, 18 Jan 2024 10:58:17 -0500 X-MC-Unique: 1oNEHh_KNIiebxOVhiJYUg-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A0A6F29AA389; Thu, 18 Jan 2024 15:58:14 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.126]) by smtp.corp.redhat.com (Postfix) with SMTP id 3709C492BE3; Thu, 18 Jan 2024 15:58:09 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 18 Jan 2024 16:57:02 +0100 (CET) Date: Thu, 18 Jan 2024 16:56:55 +0100 From: Oleg Nesterov To: Dylan Hatch Cc: Andrew Morton , Kees Cook , Frederic Weisbecker , "Joel Fernandes (Google)" , Ard Biesheuvel , "Matthew Wilcox (Oracle)" , Thomas Gleixner , Sebastian Andrzej Siewior , "Eric W. Biederman" , Vincent Whitchurch , Dmitry Vyukov , Luis Chamberlain , Mike Christie , David Hildenbrand , Catalin Marinas , Stefan Roesch , Joey Gouly , Josh Triplett , Helge Deller , Ondrej Mosnacek , Florent Revest , Miguel Ojeda , linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] getrusage: Use trylock when getting sighand lock. Message-ID: <20240118155655.GA8174@redhat.com> References: <20240117192534.1327608-1-dylanbhatch@google.com> <20240117204416.GB32526@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240117204416.GB32526@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 On 01/17, Oleg Nesterov wrote: > > Heh ;) > > getrusage() should not use ->siglock at all. > > On my TODO list. I'll try to make a patch this week. something like below... I need to re-check this change, split it into 2 patches, and write the changelogs. Hopefully tomorrow. Oleg. --- diff --git a/kernel/sys.c b/kernel/sys.c index e219fcfa112d..0728744a90a6 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1785,21 +1785,24 @@ 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; + unsigned int seq = 0; +retry: memset((char *)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)) - return; + flags = read_seqbegin_or_lock_irqsave(&sig->stats_lock, &seq); switch (who) { case RUSAGE_BOTH: @@ -1819,9 +1822,6 @@ 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; @@ -1830,28 +1830,42 @@ void getrusage(struct task_struct *p, int who, struct rusage *r) r->ru_oublock += sig->oublock; if (maxrss < sig->maxrss) maxrss = sig->maxrss; + + rcu_read_lock(); __for_each_thread(sig, t) accumulate_thread_rusage(t, r); + rcu_read_unlock(); + break; default: BUG(); } - 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 (need_seqretry(&sig->stats_lock, seq)) { + seq = 1; + goto retry; + } + done_seqretry_irqrestore(&sig->stats_lock, seq, flags); - if (who != RUSAGE_CHILDREN) { - struct mm_struct *mm = get_task_mm(p); + if (who == RUSAGE_CHILDREN) + goto done; - if (mm) { - setmax_mm_hiwater_rss(&maxrss, mm); - mmput(mm); - } + 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); } + +done: 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)