Messages in this thread | | | From | Dmitry Torokhov <> | Date | Sat, 14 Jul 2018 11:07:21 +0300 | Subject | Re: [PATCH 06/18] staging: gasket: fix deadlock in pci driver unregister path |
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On Sat, Jul 14, 2018 at 8:58 AM Todd Poynor <toddpoynor@gmail.com> wrote: > > From: Todd Poynor <toddpoynor@google.com> > > g_mutex held across pci_unregister_driver() call, also held in > gasket_pci_remove(), which deadlocks. > > Reported-by: Dmitry Torokhov <dtor@chromium.org> > Signed-off-by: Zhongze Hu <frankhu@chromium.org> > Signed-off-by: Todd Poynor <toddpoynor@google.com> > --- > drivers/staging/gasket/gasket_core.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/drivers/staging/gasket/gasket_core.c b/drivers/staging/gasket/gasket_core.c > index 3bdf7d36b397..6d240dc59557 100644 > --- a/drivers/staging/gasket/gasket_core.c > +++ b/drivers/staging/gasket/gasket_core.c > @@ -668,13 +668,10 @@ static void gasket_pci_remove(struct pci_dev *pci_dev) > struct gasket_dev *gasket_dev = NULL; > const struct gasket_driver_desc *driver_desc; > /* Find the device desc. */ > - mutex_lock(&g_mutex); > + __must_hold(&g_mutex);
And what exactly ensures that mutex is held here? Yes, we are holding the mutex when we unload the driver, but PCI hot-unplug or unbinding the device though sysfs do not go through module unload code path, so you'll end up here without holding the mutex.
> internal_desc = lookup_internal_desc(pci_dev); > - if (!internal_desc) { > - mutex_unlock(&g_mutex); > + if (!internal_desc) > return; > - } > - mutex_unlock(&g_mutex); > > driver_desc = internal_desc->driver_desc;
Thanks, Dmitry
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