Messages in this thread | | | Date | Tue, 17 Aug 2010 20:42:55 +0200 | From | Jean Delvare <> | Subject | Re: [PATCH] hwmon: (ads7871) Fix ads7871_probe error path |
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On Tue, 17 Aug 2010 08:15:59 -0700, Paul Thomas wrote: > On Tue, Aug 17, 2010 at 4:07 AM, Jean Delvare <khali@linux-fr.org> wrote: > > Hi Alex, > > > > On Mon, 16 Aug 2010 09:31:17 +0800, Axel Lin wrote: > >> We need to call hwmon_device_unregister() if an error is detected after > >> sucessfully register hwmon device. > >> > >> Signed-off-by: Axel Lin <axel.lin@gmail.com> > >> --- > >> drivers/hwmon/ads7871.c | 4 +++- > >> 1 files changed, 3 insertions(+), 1 deletions(-) > >> > >> diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c > >> index b300a20..303db92 100644 > >> --- a/drivers/hwmon/ads7871.c > >> +++ b/drivers/hwmon/ads7871.c > >> @@ -201,11 +201,13 @@ static int __devinit ads7871_probe(struct spi_device *spi) > >> we need to make sure we really have a chip*/ > >> if (val != ret) { > >> err = -ENODEV; > >> - goto error_remove; > >> + goto error_unregister; > >> } > >> > >> return 0; > >> > >> +error_unregister: > >> + hwmon_device_unregister(pdata->hwmon_dev); > >> error_remove: > >> sysfs_remove_group(&spi->dev.kobj, &ads7871_group); > >> error_free: > > > > The bug is real, but I don't think the fix is correct. You should never > > have to unregister the hwmon device in the error path, because you > > should ensure the hardware is there and working _before_ you register > > the hwmon device. > > > > User-space could watch for hwmon devices being added or removed, and > > you don't want to trigger such events for a device which isn't going to > > work. > > > > So I would suggest reworking the order in which things are done, > > leaving hwmon_device_register() at the end of the function. This won't > > only fix the error path, this will also close a race window, as for the > > moment, the device is exposed to user-space _before_ it it properly > > initialized, which is wrong. > > > > Please send an updated patch and I'll be happy to apply it. > > > > -- > > Jean Delvare > > > > Should the kzalloc, sysfs_create_group and hwmon_device_register all > stay in the same order just following the register check? I can send a > patch for that.
Axel already sent an updated patch, so it's all OK.
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