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From: Oleg Nesterov <oleg@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	William Preston <wpreston@suse.com>,
	Michal Hocko <mhocko@suse.com>,
	Roland McGrath <roland@hack.frob.com>,
	Andreas Schwab <schwab@suse.com>
Subject: Re: [RFC PATCH] kernel/fork: fix CLONE_CHILD_CLEARTID regression in nscd
Date: Wed, 3 Aug 2016 23:08:04 +0200	[thread overview]
Message-ID: <20160803210804.GA11549@redhat.com> (raw)
In-Reply-To: <1470039287-14643-1-git-send-email-mhocko@kernel.org>

sorry for delay, I am travelling till the end of the week.

On 08/01, Michal Hocko wrote:
>
> fec1d0115240 ("[PATCH] Disable CLONE_CHILD_CLEARTID for abnormal exit")

almost 10 years ago ;)

> has caused a subtle regression in nscd which uses CLONE_CHILD_CLEARTID
> to clear the nscd_certainly_running flag in the shared databases, so
> that the clients are notified when nscd is restarted.

So iiuc with this patch nscd_certainly_running should be cleared even if
ncsd was killed by !sig_kernel_coredump() signal, right?

> We should also check for vfork because
> this is killable since d68b46fe16ad ("vfork: make it killable").

Hmm, why? Can't understand... In any case this check doesn't look right, the
comment says "a killed vfork parent" while tsk->vfork_done != NULL means it
is a vforked child.

So if we want this change, why we can't simply do

	-	if (!(tsk->flags & PF_SIGNALED) &&
	+	if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&

?

And I think PF_SIGNALED must die in any case... but this is off-topic.

Oleg.

WARNING: multiple messages have this Message-ID (diff)
From: Oleg Nesterov <oleg@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	William Preston <wpreston@suse.com>,
	Michal Hocko <mhocko@suse.com>,
	Roland McGrath <roland@hack.frob.com>,
	Andreas Schwab <schwab@suse.com>
Subject: Re: [RFC PATCH] kernel/fork: fix CLONE_CHILD_CLEARTID regression in nscd
Date: Wed, 3 Aug 2016 23:08:04 +0200	[thread overview]
Message-ID: <20160803210804.GA11549@redhat.com> (raw)
In-Reply-To: <1470039287-14643-1-git-send-email-mhocko@kernel.org>

sorry for delay, I am travelling till the end of the week.

On 08/01, Michal Hocko wrote:
>
> fec1d0115240 ("[PATCH] Disable CLONE_CHILD_CLEARTID for abnormal exit")

almost 10 years ago ;)

> has caused a subtle regression in nscd which uses CLONE_CHILD_CLEARTID
> to clear the nscd_certainly_running flag in the shared databases, so
> that the clients are notified when nscd is restarted.

So iiuc with this patch nscd_certainly_running should be cleared even if
ncsd was killed by !sig_kernel_coredump() signal, right?

> We should also check for vfork because
> this is killable since d68b46fe16ad ("vfork: make it killable").

Hmm, why? Can't understand... In any case this check doesn't look right, the
comment says "a killed vfork parent" while tsk->vfork_done != NULL means it
is a vforked child.

So if we want this change, why we can't simply do

	-	if (!(tsk->flags & PF_SIGNALED) &&
	+	if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&

?

And I think PF_SIGNALED must die in any case... but this is off-topic.

Oleg.

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  reply	other threads:[~2016-08-03 21:08 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-01  8:14 [RFC PATCH] kernel/fork: fix CLONE_CHILD_CLEARTID regression in nscd Michal Hocko
2016-08-01  8:14 ` Michal Hocko
2016-08-03 21:08 ` Oleg Nesterov [this message]
2016-08-03 21:08   ` Oleg Nesterov
2016-08-12  9:41   ` Michal Hocko
2016-08-12  9:41     ` Michal Hocko
2016-08-19 13:25     ` Michal Hocko
2016-08-19 13:25       ` Michal Hocko
2016-08-23 15:27       ` Oleg Nesterov
2016-08-23 15:27         ` Oleg Nesterov
2016-08-23 16:03         ` Michal Hocko
2016-08-23 16:03           ` Michal Hocko

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