tree c40b03ea2eaf98ccd399e02972cbec3954dcc623
parent 0912da9f7f503b179683774e970ae5726756adb4
author Seiji Aguchi <seiji.aguchi@hds.com> 1360703081 -0800
committer chrmhoffmann <chrmhoffmann@gmail.com> 1586074811 +0200

efi_pstore: Introducing workqueue updating sysfs

commit a93bc0c6e07ed9bac44700280e65e2945d864fd4 upstream.

[Problem]
efi_pstore creates sysfs entries, which enable users to access to NVRAM,
in a write callback. If a kernel panic happens in an interrupt context,
it may fail because it could sleep due to dynamic memory allocations during
creating sysfs entries.

[Patch Description]
This patch removes sysfs operations from a write callback by introducing
a workqueue updating sysfs entries which is scheduled after the write
callback is called.

Also, the workqueue is kicked in a just oops case.
A system will go down in other cases such as panic, clean shutdown and emergency
restart. And we don't need to create sysfs entries because there is no chance for
users to access to them.

efi_pstore will be robust against a kernel panic in an interrupt context with this patch.

Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>
Acked-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
[xr: Backported to 3.4:
  - Adjust contest
  - Remove repeated definition of helper function variable_is_present]
Signed-off-by: Rui Xiang <rui.xiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>