On Tuesday, November 12, 2013 12:19 PM, Julia Lawall wrote: > On Tue, 12 Nov 2013, Jingoo Han wrote: > > On Tuesday, November 12, 2013 2:45 AM, Julia Lawall wrote: > > > > > > I was looking into the use of devm_spi_register_master. This function > > > seems to take care of registering and unregistering, but not allocation > > > and freeing. I have the impression that that is done with > > > spi_alloc_master and and spi_master_put, which are not managed functions. > > > But then I wonder how this can work? It seems that the spi_master_put > > > function should remain in the probe or remove function, and then the > > > object could be freed before it is unregistered? > > > > > > The patch 2fe7e4add3e53df7c1b97e32076f8390dd81c6b3 introduces a call to > > > devm_spi_register_master and also removes a call to spi_master_put. By my > > > reasoning, this would cause a memory leak. > > > > Hi Julia Lawall, > > > > I already checked that the patch 2fe7e4a "spi: txx9: use > > devm_spi_register_master()" is right. The call to spi_master_put() > > was duplicated. So, it should be removed. > > > > When removing the driver, the following functions are called. > > : devm_spi_unregister() > > -> spi_unregister_master() > > -> device_unregister() > > -> put_device() > > > > Also, spi_master_put() calls the following functions. > > : spi_master_put() > > -> put_device() > > > > So, put_device() is duplicated, when devm_spi_register_master() > > is used. In this case, spi_master_put() can be removed. > > spi_register_master calls device_add, which seems to increment the > reference count. So it may be that both calls to put_device are needed. > On the other hand, in that case it would be safe to invert their order. >
Hi Mark, By the way, now I am testing s3c64xx by repeating modprobe & rmmod. However, after s3c64xx_spi_remove() by rmmod, devm_spi_unregister() is not called. So, at the next calling modprobe, it makes kernel panic. On the other hand, When spi_unregister_master()& spi_master_put() are added, the kernel panic does not happen. Best regards, Jingoo Han -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
