linux-kernel - Re: [PATCH -mm 3/5][AIO]

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Date:	Tue, 5 Dec 2006 09:30:03 +0100
From:	Sébastien Dugué <sebastien.dugue@...l.net>
To:	bharata@...ibm.com
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-aio <linux-aio@...ck.org>, Andrew Morton <akpm@...l.org>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Christoph Hellwig <hch@...radead.org>,
	Zach Brown <zach.brown@...cle.com>,
	Badari Pulavarty <pbadari@...ibm.com>,
	Ulrich Drepper <drepper@...hat.com>,
	Jean Pierre Dion <jean-pierre.dion@...l.net>
Subject: Re: [PATCH -mm 3/5][AIO] - export good_sigevent()

On Mon, 4 Dec 2006 22:43:13 +0530 Bharata B Rao <bharata@...ibm.com> wrote:

> On Wed, Nov 29, 2006 at 11:32:34AM +0100, Sébastien Dugué wrote:
> > 
> > <snip> 
> > +/***
> > + * good_sigevent - check and get target task from a sigevent.
> > + * @event: the sigevent to be checked
> > + *
> > + * This function must be called with tasklist_lock held for reading.
> > + */
> > +struct task_struct * good_sigevent(sigevent_t * event)
> > +{
> > +	struct task_struct *rtn = current->group_leader;
> > +
> > +	if ((event->sigev_notify & SIGEV_THREAD_ID ) &&
> > +		(!(rtn = find_task_by_pid(event->sigev_notify_thread_id)) ||
> > +		 rtn->tgid != current->tgid ||
> > +		 (event->sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_SIGNAL))
> > +		return NULL;
> > +
> > +	if (((event->sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE) &&
> > +	    ((event->sigev_signo <= 0) || (event->sigev_signo > SIGRTMAX)))
> > +		return NULL;
> > +
> > +	return rtn;
> > +}
> 
> Here good_sigevent() doesn't take care of SIGEV_THREAD. From this comment
> from include/asm-generic/siginfo.h,
> 
> "It seems likely that SIGEV_THREAD will have to be handled from 
> userspace, libpthread transmuting it to SIGEV_SIGNAL, which the
> thread manager then catches and does the appropriate nonsense.
>  However, everything is written out here so as to not get lost."
> 
> it looks like SIGEV_THREAD should never come into kernel. But atleast
> libposix-aio does send SIGEV_THREAD all the way up to kernel.

  That's right, I had to reflect that change into libposix-aio, i.e. transmuting
SIGEV_THREAD into SIGEV_SIGNAL.

  Sébastien.
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