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From: "Sébastien Dugué" <sebastien.dugue@bull.net>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@osdl.org>, linux-aio <linux-aio@kvack.org>,
	Bharata B Rao <bharata@in.ibm.com>,
	Christoph Hellwig <hch@infradead.org>,
	Suparna Bhattacharya <suparna@in.ibm.com>,
	Ulrich Drepper <drepper@redhat.com>,
	Zach Brown <zach.brown@oracle.com>,
	Badari Pulavarty <pbadari@us.ibm.com>,
	Benjamin LaHaise <bcrl@linux.intel.com>,
	Jean Pierre Dion <jean-pierre.dion@bull.net>
Subject: Re: [PATCH -mm 4/7][AIO] - Make good_sigevent() non-static
Date: Mon, 5 Feb 2007 12:09:28 +0100	[thread overview]
Message-ID: <20070205120928.51dbc6a2@frecb000686> (raw)
In-Reply-To: <20070202180039.GA658@tv-sign.ru>


  Hi Oleg,

  thanks for your comments.

On Fri, 2 Feb 2007 21:00:39 +0300 Oleg Nesterov <oleg@tv-sign.ru> wrote:

> On 02/01, S?bastien Dugu? wrote:
> > 
> > +struct task_struct * sigevent_find_task(sigevent_t * event)
> > +{
> > +	struct task_struct *task = NULL;
> > +
> > +	if (event->sigev_signo <= 0 || event->sigev_signo > SIGRTMAX)
> > +		return NULL;
> > +
> > +	if ((event->sigev_notify & SIGEV_THREAD_ID ) == SIGEV_THREAD_ID) {
> > +		task = find_task_by_pid(event->sigev_notify_thread_id);
> > +
> > +		if (!task || task->tgid != current->tgid)
> > +			task = NULL;
> > +	} else if (event->sigev_notify == SIGEV_SIGNAL)
> > +		task = current->group_leader;
> > +
> > +	return task;
> > +}
> 
> I am afraid this is still not right. Consider
> 
> 	->sigev_notify == SIGEV_THREAD_ID | RANDOM_BIT
> 
> Now, the second "if (SIGEV_THREAD_ID)" returns a valid task. However,
> 
> 	really_put_req:
> 
> 		if (notify == SIGEV_THREAD_ID || notify == SIGEV_SIGNAL)
> 			put_task_struct();
> 
> doesn't work, so we have task_struct leak.

  Right, I'll revert back to the old code with cleanups.

> 
> Worse, this breaks posix-timers. Note that posix-timers allow SIGEV_NONE,
> the timer is not queued in that case, we shouldn't do ->sigev_signo check.
> This means that aio should check SIGEV_NONE itself.
> 
> Also, it is critical for posix-timers that SIGEV_THREAD_ID doesn't come
> with another bit (like in the example below), note the code like
> 
> 	if (sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
> 		...
> 
> IOW: good_sigevent() in its current form is very cryptic, and it _really_
> needs a cleanup, but we should not change its behaviour.

  Yep. I must admit that I didn't pay enough attention to this 10-liner,
but in the end it rightfully backfired on me.

> 
> Apart from this, I don't see other problems in the signal related code in
> this series.
> 
> Oleg.
> 

  Thanks again for your review.

  Sébastien.

  reply	other threads:[~2007-02-05 11:10 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-01  9:22 [PATCH -mm 0/7][AIO] - AIO completion signal notification v6 Sébastien Dugué
2007-02-01  9:26 ` [PATCH -mm 1/7][AIO] - Rework compat_sys_io_submit Sébastien Dugué
2007-02-01  9:29 ` [PATCH -mm 2/7][AIO] - fix aio.h includes Sébastien Dugué
2007-02-01  9:30 ` [PATCH -mm 3/7][AIO] - Fix access_ok() checks Sébastien Dugué
2007-02-01  9:30 ` [PATCH -mm 4/7][AIO] - Make good_sigevent() non-static Sébastien Dugué
2007-02-02 18:00   ` Oleg Nesterov
2007-02-05 11:09     ` Sébastien Dugué [this message]
2007-02-05 12:18     ` [PATCH -mm 4/7][AIO] Resend " Sébastien Dugué
2007-02-05 13:43       ` Oleg Nesterov
2007-02-05 16:00         ` [PATCH -mm][AIO] Fix AIO completion signal notification possible ref leak Sébastien Dugué
2007-02-05 17:13           ` Oleg Nesterov
2007-02-06  8:31             ` Sébastien Dugué
2007-02-06  9:22             ` [PATCH -mm][AIO] AIO completion signal notification fixes and cleanups Sébastien Dugué
2007-02-06 11:05               ` Oleg Nesterov
2007-02-06 11:39                 ` Sébastien Dugué
2007-02-06 11:57                 ` [PATCH -mm][AIO] AIO completion signal notification small cleanup Sébastien Dugué
2007-02-01  9:31 ` [PATCH -mm 5/7][AIO] - Make __sigqueue_free() and __sigqueue_alloc() non static Sébastien Dugué
2007-02-01  9:31 ` [PATCH -mm 6/7][AIO] - AIO completion signal notification Sébastien Dugué
2007-02-01  9:32 ` [PATCH -mm 7/7][AIO] - Add listio syscall support Sébastien Dugué

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