Changelog
- Patch 1/3
Add spin_lock_irq/spin_unlock_irq to open/close callbacks of efi_pstore
instead of moving spin_locks to a read callback.
- Patch 2/3
Replace a periodical timer with schedule_work().
- Patch 3/3
freshly create to kick a workqueue in oops case only.
[Problem]
There are following problems related to an interrupt context in
efivar/efi_pstore.
Currently, efivars enables interrupt while taking efivars->lock.
So, there is a risk to be deadlocking in a write callback of efi_pstore if
kernel panics
in interrupt context while taking efi_lock.
Also, efi_pstore creates sysfs entries ,which enable users to access to NVRAM,
in a write callback.
If a kernel panic happens in interrupt contexts, pstore may fail because it
could sleep due to dynamic
memory allocations during creating sysfs entries.
To resolve the problems above, a goal of this patchset is making
efivars/efi_pstore interrupt-safe.
[Patch Description]
Patch 1/3 efivars: Disable external interrupt while holding efivars->lock
This patch replaces spin_lock/spin_unlock with
spin_lock_irqsave/spin_lock_irqrestore to make efivars interrupt safe
Patch 2/3 efi_pstore: Introducing workqueue updating sysfs entries
This patch removes sysfs operations from write callback by introducing a
workqueue updating sysfs entries
Patch 3/3 efi_pstore: Skip scheduling a workqueue in cases other than oops
This patch restricts a schedule of a workqueue in just oops case which is
truly needed for users.
Also, a logic of erase callback is freshly created instead of sharing with a
write callback so that
its sysfs update operation works correctly.
drivers/firmware/efivars.c | 209 +++++++++++++++++++++++++++++++++++++-------
include/linux/efi.h | 3 +-
2 files changed, 179 insertions(+), 33 deletions(-)
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