From: Seiji Aguchi <seiji.aguchi@hds.com> Git-commit: e59310adf5eebce108f78b6c47bb330aae2e1666 Patch-mainline: v3.9-rc1 References: bnc#808680 Target: openSUSE 12.3 [Issue] There is a scenario which efi_pstore may hang up: - cpuA grabs efivars->lock - cpuB panics and calls smp_send_stop - smp_send_stop sends IRQ to cpuA - after 1 second, cpuB gives up on cpuA and sends an NMI instead - cpuA is now in an NMI handler while still holding efivars->lock - cpuB is deadlocked This case may happen if a firmware has a bug and cpuA is stuck talking with it. [Solution] This patch changes a spin_lock to a spin_trylock in non-blocking paths. and if the spin_lock has already taken by another cpu, it returns without accessing to a firmware to avoid the deadlock. Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com> Acked-by: Don Zickus <dzickus@redhat.com> Signed-off-by: Tony Luck <tony.luck@intel.com> Acked-by: Lee, Chun-Yi <jlee@suse.com> --- drivers/firmware/efivars.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) --- a/drivers/firmware/efivars.c +++ b/drivers/firmware/efivars.c @@ -1194,7 +1194,16 @@ static int efi_pstore_write(enum pstore_ sprintf(stub_name, "dump-type%u-%u-", type, part); sprintf(name, "%s%lu", stub_name, get_seconds()); - spin_lock(&efivars->lock); + if (pstore_cannot_block_path(reason)) { + /* + * If the lock is taken by another cpu in non-blocking path, + * this driver returns without entering firmware to avoid + * hanging up. + */ + if (!spin_trylock(&efivars->lock)) + return -EBUSY; + } else + spin_lock(&efivars->lock); /* * Check if there is a space enough to log. -- To unsubscribe, e-mail: opensuse-kernel+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-kernel+owner@opensuse.org