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Date: Tue, 14 Jul 2015 19:47:03 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Andrey Vagin <avagin@openvz.org>
Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Cyrill Gorcunov <gorcunov@openvz.org>,
        Pavel Emelyanov <xemul@parallels.com>, Roger Luethi <rl@hellgate.ch>,
        Arnd Bergmann <arnd@arndb.de>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        David Ahern <dsahern@gmail.com>, Andy Lutomirski <luto@amacapital.net>,
        Pavel Odintsov <pavel.odintsov@gmail.com>
Subject: Re: [PATCH 20/24] task_diag: Only add VMAs for thread_group leader
Message-ID: <20150714174703.GA8088@redhat.com>
References: <1436172445-6979-1-git-send-email-avagin@openvz.org> <1436172445-6979-21-git-send-email-avagin@openvz.org>
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On 07/06, Andrey Vagin wrote:
>
> From: David Ahern <dsahern@gmail.com>
>
> threads of a process share the same VMAs, so when dumping all threads
> for all processes only push vma data for group leader.

...

> @@ -492,6 +493,13 @@ static int task_diag_fill(struct task_struct *tsk, struct sk_buff *skb,
>  	}
>  
>  	if (show_flags & TASK_DIAG_SHOW_VMA) {
> +		/* if the request is to dump all threads of all processes
> +		 * only show VMAs for group leader.
> +		 */
> +		if (req->dump_strategy == TASK_DIAG_DUMP_ALL_THREAD &&
> +		    !thread_group_leader(tsk))
> +			goto done;
> +

This doesn't look right, group leader can be a zombie with ->mm == NULL,

>  		if (i >= n)
>  			err = fill_vma(tsk, skb, cb, &progress, show_flags);

so this probably needs something like find_lock_task_mm().

Oleg.


From mboxrd@z Thu Jan  1 00:00:00 1970
From: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH 20/24] task_diag: Only add VMAs for thread_group leader
Date: Tue, 14 Jul 2015 19:47:03 +0200
Message-ID: <20150714174703.GA8088@redhat.com>
References: <1436172445-6979-1-git-send-email-avagin@openvz.org> <1436172445-6979-21-git-send-email-avagin@openvz.org>
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To: Andrey Vagin <avagin-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Cyrill Gorcunov <gorcunov-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>, Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>, Roger Luethi <rl-7uj+XXdSDtwfv37vnLkPlQ@public.gmane.org>, Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>, Arnaldo Carvalho de Melo <acme-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, David Ahern <dsahern-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>, Pavel Odintsov <pavel.odintsov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
List-Id: linux-api@vger.kernel.org

On 07/06, Andrey Vagin wrote:
>
> From: David Ahern <dsahern-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>
> threads of a process share the same VMAs, so when dumping all threads
> for all processes only push vma data for group leader.

...

> @@ -492,6 +493,13 @@ static int task_diag_fill(struct task_struct *tsk, struct sk_buff *skb,
>  	}
>  
>  	if (show_flags & TASK_DIAG_SHOW_VMA) {
> +		/* if the request is to dump all threads of all processes
> +		 * only show VMAs for group leader.
> +		 */
> +		if (req->dump_strategy == TASK_DIAG_DUMP_ALL_THREAD &&
> +		    !thread_group_leader(tsk))
> +			goto done;
> +

This doesn't look right, group leader can be a zombie with ->mm == NULL,

>  		if (i >= n)
>  			err = fill_vma(tsk, skb, cb, &progress, show_flags);

so this probably needs something like find_lock_task_mm().

Oleg.