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From: Mike Rapoport <rppt@linux.vnet.ibm.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Darren Hart <dvhart@infradead.org>,
	Balbir Singh <bsingharora@gmail.com>,
	linux-mm <linux-mm@kvack.org>,
	lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] pids: introduce find_get_task_by_vpid helper
Date: Thu, 26 Oct 2017 22:54:47 +0300	[thread overview]
Message-ID: <20171026195442.GA10558@rapoport-lnx> (raw)
In-Reply-To: <20171026135825.GA16528@redhat.com>

On Thu, Oct 26, 2017 at 03:58:25PM +0200, Oleg Nesterov wrote:
> On 10/26, Mike Rapoport wrote:
> >
> > There are several functions that do find_task_by_vpid() followed by
> > get_task_struct(). We can use a helper function instead.
> 
> Yes, agreed, I was going to do this many times.
> 
> > --- a/kernel/futex.c
> > +++ b/kernel/futex.c
> > @@ -870,12 +870,7 @@ static struct task_struct *futex_find_get_task(pid_t pid)
> >  {
> >  	struct task_struct *p;
> >  
> > -	rcu_read_lock();
> > -	p = find_task_by_vpid(pid);
> > -	if (p)
> > -		get_task_struct(p);
> > -
> > -	rcu_read_unlock();
> > +	p = find_get_task_by_vpid(pid);
> >  
> >  	return p;
> 
> OK, but then I think you should remove futex_find_get_task() and convert
> it callers to use the new helper.

Agree. My cocci script was too simple :)
 
> > @@ -1103,11 +1103,7 @@ static struct task_struct *ptrace_get_task_struct(pid_t pid)
> >  {
> >  	struct task_struct *child;
> >  
> > -	rcu_read_lock();
> > -	child = find_task_by_vpid(pid);
> > -	if (child)
> > -		get_task_struct(child);
> > -	rcu_read_unlock();
> > +	child = find_get_task_by_vpid(pid);
> >  
> >  	if (!child)
> >  		return ERR_PTR(-ESRCH);
> 
> The same. ptrace_get_task_struct() should die imo.

Yeah, we could just return -ESRCH in ptrace_get_task_struct users instead
of all the ERR_PTR and PTR_ERR conversions...

> Oleg.
> 

-- 
Sincerely yours,
Mike.

WARNING: multiple messages have this Message-ID (diff)
From: Mike Rapoport <rppt@linux.vnet.ibm.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Darren Hart <dvhart@infradead.org>,
	Balbir Singh <bsingharora@gmail.com>,
	linux-mm <linux-mm@kvack.org>,
	lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] pids: introduce find_get_task_by_vpid helper
Date: Thu, 26 Oct 2017 22:54:47 +0300	[thread overview]
Message-ID: <20171026195442.GA10558@rapoport-lnx> (raw)
In-Reply-To: <20171026135825.GA16528@redhat.com>

On Thu, Oct 26, 2017 at 03:58:25PM +0200, Oleg Nesterov wrote:
> On 10/26, Mike Rapoport wrote:
> >
> > There are several functions that do find_task_by_vpid() followed by
> > get_task_struct(). We can use a helper function instead.
> 
> Yes, agreed, I was going to do this many times.
> 
> > --- a/kernel/futex.c
> > +++ b/kernel/futex.c
> > @@ -870,12 +870,7 @@ static struct task_struct *futex_find_get_task(pid_t pid)
> >  {
> >  	struct task_struct *p;
> >  
> > -	rcu_read_lock();
> > -	p = find_task_by_vpid(pid);
> > -	if (p)
> > -		get_task_struct(p);
> > -
> > -	rcu_read_unlock();
> > +	p = find_get_task_by_vpid(pid);
> >  
> >  	return p;
> 
> OK, but then I think you should remove futex_find_get_task() and convert
> it callers to use the new helper.

Agree. My cocci script was too simple :)
 
> > @@ -1103,11 +1103,7 @@ static struct task_struct *ptrace_get_task_struct(pid_t pid)
> >  {
> >  	struct task_struct *child;
> >  
> > -	rcu_read_lock();
> > -	child = find_task_by_vpid(pid);
> > -	if (child)
> > -		get_task_struct(child);
> > -	rcu_read_unlock();
> > +	child = find_get_task_by_vpid(pid);
> >  
> >  	if (!child)
> >  		return ERR_PTR(-ESRCH);
> 
> The same. ptrace_get_task_struct() should die imo.

Yeah, we could just return -ESRCH in ptrace_get_task_struct users instead
of all the ERR_PTR and PTR_ERR conversions...

> Oleg.
> 

-- 
Sincerely yours,
Mike.

--
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  reply	other threads:[~2017-10-26 19:55 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-26 13:07 [PATCH] pids: introduce find_get_task_by_vpid helper Mike Rapoport
2017-10-26 13:07 ` Mike Rapoport
2017-10-26 13:58 ` Oleg Nesterov
2017-10-26 13:58   ` Oleg Nesterov
2017-10-26 19:54   ` Mike Rapoport [this message]
2017-10-26 19:54     ` Mike Rapoport

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