From: Josh Boyer Date: Mon, 11 Mar 2013 21:47:42 +0000 (-0400) Subject: efivars: Disable external interrupt while holding efivars->lock X-Git-Tag: v3.2.41~43 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3b048fc196139b840d79b316405bede9b5d3c4c2;p=pandora-kernel.git efivars: Disable external interrupt while holding efivars->lock commit 81fa4e581d9283f7992a0d8c534bb141eb840a14 upstream. [Problem] 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. [Patch Description] This patch disables an external interruption while holding efivars->lock as follows. In efi_pstore_write() and get_var_data(), spin_lock/spin_unlock is replaced by spin_lock_irqsave/spin_unlock_irqrestore because they may be called in an interrupt context. In other functions, they are replaced by spin_lock_irq/spin_unlock_irq. because they are all called from a process context. By applying this patch, we can avoid the problem above with a following senario. - CPUA holds an efi_var->lock with interrupt disabled. - CPUB panics and sends IPI to CPUA in smp_send_stop(). - CPUA receives the IPI after releasing the lock because it is disabling interrupt while holding the lock. - CPUB waits for one sec until CPUA releases the lock. - CPUB kicks efi_pstore_write() via kmsg_dump(KSMG_DUMP_PANIC) And it can hold the lock successfully. Signed-off-by: Seiji Aguchi Acked-by: Mike Waychison Acked-by: Matt Fleming Signed-off-by: Tony Luck [bwh: Backported to 3.2: - Drop efivarfs changes - Adjust context - Drop change to efi_pstore_erase(), which is implemented using efi_pstore_write() here] Signed-off-by: Ben Hutchings --- Reading git-diff-tree failed