On Thu, Feb 18, 2021 at 09:27:09AM +0100, Michael Walle wrote: > Am 2021-02-18 08:31, schrieb Greg KH: > > On Wed, Feb 17, 2021 at 09:50:38PM +0000, Marc Zyngier wrote: > > > On Wed, 17 Feb 2021 20:10:50 +0000, > > > Michael Walle <mich...@walle.cc> wrote: > > > > > > > > Am 2021-02-17 21:02, schrieb Marc Zyngier: > > > > > On 2021-02-17 19:57, Michael Walle wrote: > > > > >> Hi Greg, > > > > >> > > > > >>> There's no need to keep around a dentry pointer to a simple file > > > > >>> that > > > > >>> debugfs itself can look up when we need to remove it from the > > > > >>> system. > > > > >>> So simplify the code by deleting the variable and cleaning up the > > > > >>> logic > > > > >>> around the debugfs file. > > > > >> > > > > >> This will generate the following oops on my board (arm64, > > > > >> freescale/fsl-ls1028a-kontron-sl28-var3-ads2.dts). In > > > > >> debugfs_lookup() > > > > >> debugfs_mount is NULL. > > > > > > > > > > That's odd. I gave it a go yesterday, and nothing blew up. > > > > > Which makes me wonder whether I had the debug stuff enabled > > > > > the first place... > > > > > > > > > > I've dropped the patch from -next for now until I figure it out > > > > > (probably tomorrow). > > > > > > > > Mh, maybe its my .config, I've attached it. I also noticed that > > > > the board boots just fine in our kernel-ci [1]. > > > > > > I reproduced here. I had disabled GENERIC_IRQ_DEBUGFS for obscure > > > reasons, and it caught fire as I re-enabled it. > > > > > > Adding this fixes it for me: > > > > > > diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c > > > index 367ff1c35f75..d8a14cf1a7b6 100644 > > > --- a/kernel/irq/irqdomain.c > > > +++ b/kernel/irq/irqdomain.c > > > @@ -1904,7 +1904,8 @@ static void debugfs_add_domain_dir(struct > > > irq_domain *d) > > > > > > static void debugfs_remove_domain_dir(struct irq_domain *d) > > > { > > > - debugfs_remove(debugfs_lookup(d->name, domain_dir)); > > > + if (domain_dir) > > > + debugfs_remove(debugfs_lookup(d->name, domain_dir)); > > > } > > > > > > void __init irq_domain_debugfs_init(struct dentry *root) > > > > > > > > > Could you please check whether it works for you? > > > > Can you try this debugfs core change instead? Callers to debugfs should > > not have to do the above type of checking as debugfs should be much more > > robust than that. > > > > thanks, > > > > greg k-h > > > > > > diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c > > index 2fcf66473436..5aa798f52b6e 100644 > > --- a/fs/debugfs/inode.c > > +++ b/fs/debugfs/inode.c > > @@ -297,7 +297,7 @@ struct dentry *debugfs_lookup(const char *name, > > struct dentry *parent) > > { > > struct dentry *dentry; > > > > - if (IS_ERR(parent)) > > + if (IS_ERR_OR_NULL(name) || IS_ERR(parent)) > > return NULL; > > > > if (!parent) > > This doesn't work. name is not NULL when it is called.
Ok, but it is a good check we need to make anyway, I'll add it to a patch series :) > What has to happen before debugfs_lookup() can be called? Looks like > someone has to initialize the static debugfs_mount, first. Wow, wait, you are removing a debugfs file _before_ debugfs is even initialized? Didn't expect that, ok, let me go try this again... thanks, greg k-h