ACPI: NFIT: core: Fix possible deadlock and missing notifications

After commit 9b311b7313d6 ("ACPI: NFIT: Install Notify() handler before
getting NFIT table"), ACPI NFIT driver removal may deadlock if an ACPI
notify on the NFIT device is triggered concurrently.  A similar deadlock
may occur if an ACPI notify on the NFIT device is triggered during a
failing driver probe.

The deadlock is possible because acpi_dev_remove_notify_handler() calls
acpi_os_wait_events_complete() after removing the notify handler and the
driver core invokes it under the NFIT platform device lock which is also
acquired by acpi_nfit_notify().  Thus acpi_os_wait_events_complete() may
be waiting for acpi_nfit_notify() to complete, but the latter may not be
able to acquire the device lock which is being held by the driver core
while the former is being executed.

Moreover, after commit 03667e146f81 ("ACPI: NFIT: core: Convert the
driver to a platform one"), there are no sysfs notifications regarding
NVDIMM devices because __acpi_nvdimm_notify() always bails out after
checking the driver data pointer of the device's parent.  That parent
is the ACPI companion of the platform device used for driver binding,
so its driver data pointer is always NULL after the commit in question
which was overlooked by it.

A remedy for the deadlock is to use a special separate lock for ACPI
notify synchronization with driver probe and removal instead of the
device lock of the NFIT device, while a remedy for the second issue
is to populate the driver data pointer of the NFIT device's ACPI
companion when the driver is ready to operate, so do both these things.
However, since the new lock is not held across the entire teardown and
acpi_nfit_notify() should do nothing when teardown is in progress, make
it check the driver data pointer of the NFIT device's ACPI companion, in
analogy with the existing check in __acpi_nvdimm_notify(), and bail out
if that pointer is NULL.

Fixes: 9b311b7313d6 ("ACPI: NFIT: Install Notify() handler before getting NFIT table")
Fixes: 03667e146f81 ("ACPI: NFIT: core: Convert the driver to a platform one")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: All applicable <stable@vger.kernel.org> # 9995e4404ea4: ACPI: NFIT: core: Eliminate redundant local variable
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/3420096.aeNJFYEL58@rafael.j.wysocki

0 files changed, 0 insertions, 0 deletions