linux-kernel - Re: [PATCH] [media] staging: Return -EINTR in s2250

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Message-Id: <201203161859.35104.oliver@neukum.org>
Date:	Fri, 16 Mar 2012 18:59:35 +0100
From:	Oliver Neukum <oliver@...kum.org>
To:	santosh prasad nayak <santoshprasadnayak@...il.com>
Cc:	mchehab@...radead.org, gregkh@...uxfoundation.org,
	khoroshilov@...ras.ru, linux-media@...r.kernel.org,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] [media] staging: Return -EINTR in s2250_probe() if fails to get lock.

Am Freitag, 16. März 2012, 17:56:20 schrieb santosh prasad nayak:
> On Fri, Mar 16, 2012 at 10:02 PM, Oliver Neukum <oliver@...kum.org> wrote:
> >
> > Indeed there's a lot wrong here. The idea of having an interruptible
> > sleep in probe() is arcane. You need a very, very, very good reason for that.
> 
> Can you please explain why interruptible  sleep  should not be  in probe() ?
> I am curious to know.

-EINTR is supposed to be returned to user space, so that it can repeat
an interrupted syscall.

- There is no user space for probe()
- probe() cannot be easily repeated from user space
- there is no syscall for probe
> 
> 
> > The sane fix is using an uninterruptable sleep here.
> >
> > Second, while you are at it, fix the error case for no initialization
> > due to a failing kmalloc(). You need to return -ENOMEM.
> 
> Are you talking about kmalloc or kzalloc ?
> Because for failing kmalloc -ENOMEM is returned as shown below:

                data = kzalloc(16, GFP_KERNEL);
                if (data != NULL) {
                        int rc;
                        rc = go7007_usb_vendor_request(go, 0x41, 0, 0,
                                                       data, 16, 1);
                        if (rc > 0) {
                                u8 mask;
                                data[0] = 0;
                                mask = 1<<5;
                                data[0] &= ~mask;
                                data[1] |= mask;
                                go7007_usb_vendor_request(go, 0x40, 0,
                                                          (data[1]<<8)
                                                          + data[1],
                                                          data, 16, 0);
                        }
                        kfree(data);
                }
                mutex_unlock(&usb->i2c_lock)

This code has no error handling.

	Regards
		Oliver
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