From: Vishal Verma vishal.l.verma@intel.com
[ Upstream commit fb6df4366f86dd252bfa3049edffa52d17e7b895 ]
Lockdep reports that acpi_nfit_shutdown() may deadlock against an opportune acpi_nfit_scrub(). acpi_nfit_scrub () is run from inside a 'work' and therefore has already acquired workqueue-internal locks. It also acquiires acpi_desc->init_mutex. acpi_nfit_shutdown() first acquires init_mutex, and was subsequently attempting to cancel any pending workqueue items. This reversed locking order causes a potential deadlock:
====================================================== WARNING: possible circular locking dependency detected 6.2.0-rc3 #116 Tainted: G O N ------------------------------------------------------ libndctl/1958 is trying to acquire lock: ffff888129b461c0 ((work_completion)(&(&acpi_desc->dwork)->work)){+.+.}-{0:0}, at: __flush_work+0x43/0x450
but task is already holding lock: ffff888129b460e8 (&acpi_desc->init_mutex){+.+.}-{3:3}, at: acpi_nfit_shutdown+0x87/0xd0 [nfit]
which lock already depends on the new lock.
...
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(&acpi_desc->init_mutex); lock((work_completion)(&(&acpi_desc->dwork)->work)); lock(&acpi_desc->init_mutex); lock((work_completion)(&(&acpi_desc->dwork)->work));
*** DEADLOCK ***
Since the workqueue manipulation is protected by its own internal locking, the cancellation of pending work doesn't need to be done under acpi_desc->init_mutex. Move cancel_delayed_work_sync() outside the init_mutex to fix the deadlock. Any work that starts after acpi_nfit_shutdown() drops the lock will see ARS_CANCEL, and the cancel_delayed_work_sync() will safely flush it out.
Reported-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Vishal Verma vishal.l.verma@intel.com Link: https://lore.kernel.org/r/20230112-acpi_nfit_lockdep-v1-1-660be4dd10be@intel... Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/acpi/nfit/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c index 99e23a5df0267..2306abb09f7f5 100644 --- a/drivers/acpi/nfit/core.c +++ b/drivers/acpi/nfit/core.c @@ -3687,8 +3687,8 @@ void acpi_nfit_shutdown(void *data)
mutex_lock(&acpi_desc->init_mutex); set_bit(ARS_CANCEL, &acpi_desc->scrub_flags); - cancel_delayed_work_sync(&acpi_desc->dwork); mutex_unlock(&acpi_desc->init_mutex); + cancel_delayed_work_sync(&acpi_desc->dwork);
/* * Bounce the nvdimm bus lock to make sure any in-flight