RE: [RESEND][PATCH v4 0/3] make efivars/efi_pstore interrupt-safe

From: Seiji Aguchi
Date: Tue Sep 04 2012 - 18:14:46 EST


Matthew,

Could you please review this patchset?
I talked to Tony about it in Plumbers conference last week and he told that your review is needed because it is efi-specific.

Seiji

> -----Original Message-----
> From: linux-kernel-owner@xxxxxxxxxxxxxxx [mailto:linux-kernel-owner@xxxxxxxxxxxxxxx] On Behalf Of Seiji Aguchi
> Sent: Tuesday, September 04, 2012 6:06 PM
> To: Mike Waychison; linux-kernel@xxxxxxxxxxxxxxx; Luck, Tony (tony.luck@xxxxxxxxx); Matthew Garrett (mjg@xxxxxxxxxx);
> dzickus@xxxxxxxxxx; linux-efi@xxxxxxxxxxxxxxx
> Cc: dle-develop@xxxxxxxxxxxxxxxxxxxxx; Satoru Moriya
> Subject: [RESEND][PATCH v4 0/3] make efivars/efi_pstore interrupt-safe
>
> Changelog
> v3 -> v4
> - Patch 2/3
> Move cancel_work_sync() above an efi_enabled test in efivars_exit().
>
> v2 -> v3
> - Patch 1/3
> Replace spin_lock_irqsave/spin_unlock_irqrestore with spin_lock_irq/spin_unlock_irq in efivars_unregister(),
> efivar_create(), efivar_store_raw() and efivar_delete() which are called in a process context.
>
> - Patch 2/3
> Change a name of delete_sysfs_entry() to delete_all_stale_sysfs_entries().
> Also, don't release an efivar->lock while searching efivar->list in delete_all_stale_sysfs_entries().
>
> - Patch 3/3
> Remove a logic in efi_pstore_erase() which freshly created in patch v2.
>
> v1 -> v2
> - 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: Skiping scheduling a workqueue in cases other than oops
> This patch restricts a schedule of a workqueue in case where users erase entries or oops happen which is truly needed for users.
>
> drivers/firmware/efivars.c | 167 +++++++++++++++++++++++++++++++++++--------
> include/linux/efi.h | 3 +-
> 2 files changed, 138 insertions(+), 32 deletions(-)
>
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