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author | Vishal Verma <vishal.l.verma@intel.com> | 2023-01-25 11:34:18 -0700 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-03-03 11:52:21 +0100 |
commit | fdbcacfe495dc3faa9d49872a2c40f25fc069f27 (patch) | |
tree | db613a612b0dbe0397d3af1f0eb1bd18de146206 | |
parent | 1b7730f203559481edefb06dca743bea01a6e138 (diff) | |
download | linux-fdbcacfe495dc3faa9d49872a2c40f25fc069f27.tar.gz |
ACPI: NFIT: fix a potential deadlock during NFIT teardown
[ 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.com Signed-off-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
-rw-r--r-- | drivers/acpi/nfit/core.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c index ae5f4acf2675..6d4ac934cd49 100644 --- a/drivers/acpi/nfit/core.c +++ b/drivers/acpi/nfit/core.c @@ -3297,8 +3297,8 @@ 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 |