On Mon, 14 Apr 2014 17:11:12 +0200 Igor Mammedov <imammedo@xxxxxxxxxx> wrote: > changes since v3: > * put simple bugfixes first > * move common part of syncing with master CPU in cpu_init() > for x32/64 variant into helper function > * cpu_init(): WARN_ON if cpu_initialized_mask is set > * fix panic on CPU unplug, caused by erroneous removing > of "pr->dev = dev;" in drivers/acpi/acpi_processor.c Hi guys, It seems there won't be more comments on series, could you review it, please? > > -- > Hang is observed on virtual machines during CPU hotplug, > especially in big guests with many CPUs. (It happens more > often if host is over-committed). > > Hang happens because master CPU timeouts on waiting till > AP boots and 'cancels' CPU online operation assuming AP > is not functional but AP may continue run wild later > causing various hangs or panics in running kernel that > is assuming that AP was offline. > > This is an alternative approach, that instead of canceling > in-progress AP bringup (https://lkml.org/lkml/2014/3/6/257), > removes timeouts so that AP bringup won't be affected by > poor timing and syncs AP with master CPU at early startup > making sure that AP won't run wild if master CPU doesn't > expect AP to come online. > > Series also fixes 3 bugs found during testing CPU bringup > failure case. > > -- > Below is the detailed description of a more often happening hang: > --- > Master CPU may timeout before cpu_callin_mask is set and cancel > booting CPU, but being onlined CPU still continues to boot, sets > cpu_active_mask (CPU_STARTING notifiers) and spins in > check_tsc_sync_target() for master cpu to arrive. Following attempt > to online another cpu hangs in stop_machine, initiated from here: > smp_callin -> > smp_store_cpu_info -> > identify_secondary_cpu -> > mtrr_ap_init -> set_mtrr_from_inactive_cpu > > stop_machine waits on completion of stop_work on all CPUs from > cpu_active_mask including a failed CPU that spins in check_tsc_sync_target(). > > > Igor Mammedov (5): > x86: fix list corruption on CPU hotplug > x86: fix memory corruption in acpi_unmap_lsapic() > acpi_processor: do not mark present at boot but not onlined CPU as > onlined > x86: log error on secondary CPU wakeup failure at ERR level > x86: initialize secondary CPU only if master CPU will wait for it > > arch/x86/kernel/cpu/common.c | 27 ++++++---- > arch/x86/kernel/smpboot.c | 103 ++++++++++++---------------------------- > drivers/acpi/acpi_processor.c | 1 - > 3 files changed, 47 insertions(+), 84 deletions(-) > -- Regards, Igor -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
