On Wed, 7 Apr 2021 at 09:55, William A. Kennington III <wak@xxxxxxxxxx> wrote: > > We can't rely on the contents of the devres list during > spi_unregister_controller(), as the list is already torn down at the > time we perform devres_find() for devm_spi_release_controller. This > causes devices registered with devm_spi_alloc_{master,slave}() to be > mistakenly identified as legacy, non-devm managed devices and have their > reference counters decremented below 0. Thanks for spending the time to track down the bug and sending a fix for it. I appreciate it! Reviewed-by: Joel Stnaley <joel@xxxxxxxxx> Cheers, Joel > > ------------[ cut here ]------------ > WARNING: CPU: 1 PID: 660 at lib/refcount.c:28 refcount_warn_saturate+0x108/0x174 > [<b0396f04>] (refcount_warn_saturate) from [<b03c56a4>] (kobject_put+0x90/0x98) > [<b03c5614>] (kobject_put) from [<b0447b4c>] (put_device+0x20/0x24) > r4:b6700140 > [<b0447b2c>] (put_device) from [<b07515e8>] (devm_spi_release_controller+0x3c/0x40) > [<b07515ac>] (devm_spi_release_controller) from [<b045343c>] (release_nodes+0x84/0xc4) > r5:b6700180 r4:b6700100 > [<b04533b8>] (release_nodes) from [<b0454160>] (devres_release_all+0x5c/0x60) > r8:b1638c54 r7:b117ad94 r6:b1638c10 r5:b117ad94 r4:b163dc10 > [<b0454104>] (devres_release_all) from [<b044e41c>] (__device_release_driver+0x144/0x1ec) > r5:b117ad94 r4:b163dc10 > [<b044e2d8>] (__device_release_driver) from [<b044f70c>] (device_driver_detach+0x84/0xa0) > r9:00000000 r8:00000000 r7:b117ad94 r6:b163dc54 r5:b1638c10 r4:b163dc10 > [<b044f688>] (device_driver_detach) from [<b044d274>] (unbind_store+0xe4/0xf8) > > Instead, determine the devm allocation state as a flag on the > controller which is guaranteed to be stable during cleanup. > > Fixes: 5e844cc37a5c ("spi: Introduce device-managed SPI controller allocation") > Signed-off-by: William A. Kennington III <wak@xxxxxxxxxx> > --- > drivers/spi/spi.c | 9 ++------- > include/linux/spi/spi.h | 3 +++ > 2 files changed, 5 insertions(+), 7 deletions(-) > > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c > index b08efe88ccd6..904a353798b6 100644 > --- a/drivers/spi/spi.c > +++ b/drivers/spi/spi.c > @@ -2496,6 +2496,7 @@ struct spi_controller *__devm_spi_alloc_controller(struct device *dev, > > ctlr = __spi_alloc_controller(dev, size, slave); > if (ctlr) { > + ctlr->devm_allocated = true; > *ptr = ctlr; > devres_add(dev, ptr); > } else { > @@ -2842,11 +2843,6 @@ int devm_spi_register_controller(struct device *dev, > } > EXPORT_SYMBOL_GPL(devm_spi_register_controller); > > -static int devm_spi_match_controller(struct device *dev, void *res, void *ctlr) > -{ > - return *(struct spi_controller **)res == ctlr; > -} > - > static int __unregister(struct device *dev, void *null) > { > spi_unregister_device(to_spi_device(dev)); > @@ -2893,8 +2889,7 @@ void spi_unregister_controller(struct spi_controller *ctlr) > /* Release the last reference on the controller if its driver > * has not yet been converted to devm_spi_alloc_master/slave(). > */ > - if (!devres_find(ctlr->dev.parent, devm_spi_release_controller, > - devm_spi_match_controller, ctlr)) > + if (!ctlr->devm_allocated) > put_device(&ctlr->dev); > > /* free bus id */ > diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h > index 592897fa4f03..643139b1eafe 100644 > --- a/include/linux/spi/spi.h > +++ b/include/linux/spi/spi.h > @@ -510,6 +510,9 @@ struct spi_controller { > > #define SPI_MASTER_GPIO_SS BIT(5) /* GPIO CS must select slave */ > > + /* flag indicating this is a non-devres managed controller */ > + bool devm_allocated; > + > /* flag indicating this is an SPI slave controller */ > bool slave; > > -- > 2.31.0.208.g409f899ff0-goog >