On Mon, Dec 17, 2012 at 08:56:27PM +0000, Seiji Aguchi wrote: > Changelog v1 -> v2 > - Erase a logic checking the number of online cpus. > - Create a patchset to fix deadlocking issue in both pstore filesystem and > efi_pstore driver. > - Introduce a function, is_non_blocking_path(), to check if pstore > is in panic and emergency-restart paths (PATCH 1/2) > - Avoid efi_pstore_driver is blocked in non-blocking paths > such as nmi, panic and emergency-restart paths (PATCH 2/2)
This patch set seems cleaner. Though it seems most of patch2 should have been in patch1 (except for the efi part). The only nitpick I have is the name 'is_non_blocking_path'. I don't know why, but the name doesn't seem exactly right to me. I was thinking something like 'pstore_cannot_block_path' or something. But it is just a nitpick, so it doesn't matter either way to me. Cheers, Don > > [Issue] > > There are some paths which shouldn't be blocked in kernel, like NMI, panic > case after stopping cpus, > emergency-restart. > > On the other hand, current pstore avoids blocking in a NMI path but it may be > blocked in other paths. > Also, an efi_pstore driver may be blocked in all of those paths because it > simply takes a spin lock > at writing time. > > If they are blocked in those paths, the system will hang up and it has a big > impact for users. > > Here is an example scenario which pstore is blocked in panic path. > > - cpuA grabs psinfo->buf_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 buf_lock. > And then, cpuB is deadlocked by taking efi_pstore->lock again. > > This case may happen if a firmware has a bug and cpuA is stuck in it. > > [Solution] > > This patchset avoids that pstore and efi_pstore driver are blocked in the > non-blocking paths > like NMI, panic, and emrgency-restart by introducing a function checking if > they are in those paths. > Please see each patch for detailed explanations. > > Seiji Aguchi (2): > [PATCH v2 1/2] pstore: Avoid deadlock in panic and emergency-restart path > [PATCH v2 2/2] efi_pstore: Avoid deadlock in non-blocking paths > > drivers/firmware/efivars.c | 11 ++++++++++- > fs/pstore/platform.c | 34 ++++++++++++++++++++++++++++------ > include/linux/pstore.h | 6 ++++++ > 3 files changed, 44 insertions(+), 7 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
