[RFC][PATCH 0/2] make efivars/efi_pstore interrupt-safe

[Seiji Aguchi]

[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 1/2 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 2/2 efi_pstore: Introducing workqueue updating sysfs entries
   This patch removes sysfs operations from write callback by introducing a workqueue updating sysfs entries

 drivers/firmware/efivars.c |  193 +++++++++++++++++++++++++++++++++++---------
 include/linux/efi.h        |    6 +-
 2 files changed, 161 insertions(+), 38 deletions(-)

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