Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> wrote: >On Wed, Sep 18, 2013 at 05:12:02PM +0100, Jonathan Cameron wrote: >> >> >> Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> wrote: >> >On Wed, Sep 18, 2013 at 10:39:42AM +0100, Jonathan Cameron wrote: >> >> >> >> >> >> "Zubair Lutfullah :" <zubair.lutfullah@xxxxxxxxx> wrote: >> >> >On Tue, Sep 17, 2013 at 09:27:27PM -0700, Dmitry Torokhov wrote: >> >> >> Hi Zubair, >> >> >> >> >> >> On Tue, Sep 17, 2013 at 09:44:07AM +0500, Zubair Lutfullah >wrote: >> >> >> > + >> >> >> > + ret = devm_request_threaded_irq(indio_dev->dev.parent, >> >> >> > + irq, >> >> >> > + pollfunc_th, pollfunc_bh, >> >> >> > + flags, indio_dev->name, >> >> >> > + indio_dev); >> >> >> > + if (ret) >> >> >> > + goto error_kfifo_free; >> >> >> > + >> >> >> > + indio_dev->setup_ops = setup_ops; >> >> >> > + indio_dev->modes |= INDIO_BUFFER_HARDWARE; >> >> >> > + >> >> >> > + ret = iio_buffer_register(indio_dev, >> >> >> > + indio_dev->channels, >> >> >> > + indio_dev->num_channels); >> >> >> > + if (ret) >> >> >> > + goto error_free_irq; >> >> >> > + >> >> >> > + return 0; >> >> >> > + >> >> >> > +error_free_irq: >> >> >> > + devm_free_irq(indio_dev->dev.parent, irq, indio_dev); >> >> >> >> >> >> What is the point of using devm_* here if you are doing >explicit >> >> >> management of the resource anyway (you explicitly release it in >> >all >> >> >code >> >> >> paths)? >> >> >> >> >> >> Thanks. >> >> >> >> >> >> -- >> >> >> Dmitry >> >> > >> >> >I admit I am unaware at the moment about how it works. >> >> > >> >> >I use devm and simply ignore the error path? >> >> > >> >> >The devm function header description said something about using >> >> >devm_free when freeing. And this is the way I am used to seeing >> >> >error handling. >> >> >> > >> >> The devm interfaces ensure this is all cleaned when the device is >> >> removed thus avoiding the need to free the stuff explicitly. >Device >> >> will get freed on deliberate remove and on an error from probe. >Hence >> >> you can drop all calls to devm free. The devm free functions are >only >> >> needed if you wish to free in order to reallocate. This might >happen >> >> if you want to change a buffer size for instance. >> > >> >However in this case such conversion us dangerous. With all but IRQ >> >resource managed by the traditional methods they will be released >first >> >with IRQ handler deregistered very last. Therefore if device is not >> >properly quiesced IRQ raised during driver unbinding is likely to >> >result >> >in kernel oops. >> > >> >IOW devm_request_irq() is very often evil (it is still useful if >_all_ >> >your resources are managed by devm_*). >> > >> >In case of your driver I'd recommend switching to >> >request_irq()/free_irq() instead. >> > >> >Thanks. >> >> Pretty much all resources are devm managed in here >> >> >https://git.kernel.org/cgit/linux/kernel/git/jic23/iio.git/tree/drivers/iio/adc/ti_am335x_adc.c?h=togreg&id=7a1aeba7ed0d5a1e83fd5a8ee2a2869430d40347 > > >So we are guaranteed that that new kfifo that is being allocated just >before we requesting IRQ and will be freed way before we free the IRQ >will not be used by the IOTQ handler? > >Thanks. Good point. I forgot about that. The source of interrupts 'should' be disabled before the kfifo is freed but I guess perhaps better to play it safe. Would take a fair bit of review to be sure that is not going to cause grief. A few more devm handlers need writing before it is truly useful here. Thanks for pointing this out. J -- Sent from my Android phone with K-9 Mail. Please excuse my brevity. -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
