linux-kernel - RE: [RESEND][PATCH v4 0/3] make efivars/efi

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Message-ID: <A5ED84D3BB3A384992CBB9C77DEDA4D413826F2E@USINDEM103.corp.hds.com>
Date:	Tue, 4 Sep 2012 22:14:15 +0000
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	"Matthew Garrett (mjg@...hat.com)" <mjg@...hat.com>
CC:	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Satoru Moriya <satoru.moriya@....com>,
	Mike Waychison <mikew@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>,
	"dzickus@...hat.com" <dzickus@...hat.com>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>
Subject: RE: [RESEND][PATCH v4 0/3] make efivars/efi_pstore interrupt-safe

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@...r.kernel.org [mailto:linux-kernel-owner@...r.kernel.org] On Behalf Of Seiji Aguchi
> Sent: Tuesday, September 04, 2012 6:06 PM
> To: Mike Waychison; linux-kernel@...r.kernel.org; Luck, Tony (tony.luck@...el.com); Matthew Garrett (mjg@...hat.com);
> dzickus@...hat.com; linux-efi@...r.kernel.org
> Cc: dle-develop@...ts.sourceforge.net; 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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