Matt, Can you please take a look at this patchset which removes create_sysfs_entries() from efi_pstore_write()? It has been updated in accordance with Mike's comment and fixes an actual bug. http://comments.gmane.org/gmane.linux.kernel.efi/406 Seiji > -----Original Message----- > From: Seiji Aguchi > Sent: Wednesday, January 23, 2013 7:41 PM > To: linux-kernel@xxxxxxxxxxxxxxx; linux-efi@xxxxxxxxxxxxxxx; Luck, Tony (tony.luck@xxxxxxxxx); mikew@xxxxxxxxxx; > matt.fleming@xxxxxxxxx; cbouatmailru@xxxxxxxxx; dzickus@xxxxxxxxxx > Cc: dle-develop@xxxxxxxxxxxxxxxxxxxxx; Satoru Moriya > Subject: [PATCH v5 -next 0/2] make efivars/efi_pstore interrupt-safe > > Changelogv4 -> v5 > - Rebase from a linus tree to a linux-next tree to avoid getting > a conflict when this patchset is merged to a linux-next tree. > - Merge previous patches 2/3 and 3/3 into 2/2 because they fix > a same problem. > - Modify to fit a latest upstream kernel as follows. > - Change spinlock operations of efivarfs which has been > introduced recently.(Patch 1/2) > - Remove delete_all_stale_sysfs_entries() from update_sysfs_entries() > because a currnet efi_pstore doesn't erase existing entries > in a write callback and sysfs entries don't become stale. > (Patch 2/2) > > 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 efivars including efivarfs and efi_pstore. > > (1)There is a scenario which efi_pstore fails to log messages > in a panic case. > > - CPUA holds an efi_var->lock in either efivarfs parts > or efi_pstore with interrupt enabled. > - CPUB panics and sends IPI to CPUA in smp_send_stop(). > - CPUA stops with holding the lock. > - CPUB kicks efi_pstore_write() via kmsg_dump(KSMG_DUMP_PANIC) > but it returns without logging messages. > > (2)Also, efi_pstore creates sysfs entries, which enable users to access to > NVRAM, in a write callback. > If a kernel panic happens in an interrupt contexts, pstore may fail > because it could sleep due to dynamic memory allocations during creating > sysfs entries. > An actual failure due to the create_sysfs_entry() has been reported. > http://comments.gmane.org/gmane.linux.kernel.efi/406 > > To resolve problems above, this patchset makes efivars/efi_pstore interrupt-safe. > > [Patch Description] > Please see detailed explanations in each patch. > > Seiji Aguchi (2): > efivars: Disable external interrupt while holding efivars->lock > - This patch fixes a problem (1). > > efi_pstore: Introducing workqueue updating sysfs entries > - This patch fixes a problem (2). > > drivers/firmware/efivars.c | 171 ++++++++++++++++++++++++++++++++------------ > include/linux/efi.h | 3 +- > 2 files changed, 126 insertions(+), 48 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
